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High molecular weight (HMW; >1 kDa) carbohydrates are a major component of dissolved organic matter (DOM) released by benthic primary producers. Despite shifts from coral to algae dominance on many reefs, little is known about the effects of exuded carbohydrates on bacterioplankton communities in reef waters. We compared the monosaccharide composition of HMW carbohydrates exuded by hard corals and brown macroalgae and investigated the response of the bacterioplankton community of an algae-dominated Caribbean reef to the respective HMW fractions. HMW coral exudates were compositionally distinct from the ambient, algae-dominated reef waters and similar to coral mucus (high in arabinose). They further selected for opportunistic bacterioplankton taxa commonly associated with coral stress (i.e., Rhodobacteraceae , Phycisphaeraceae , Vibrionaceae , and Flavobacteriales ) and significantly increased the predicted energy-, amino acid-, and carbohydrate-metabolism by 28%, 44%, and 111%, respectively. In contrast, HMW carbohydrates exuded by algae were similar to those in algae tissue extracts and reef water (high in fucose) and did not significantly alter the composition and predicted metabolism of the bacterioplankton community. These results confirm earlier findings of coral exudates supporting efficient trophic transfer, while algae exudates may have stimulated microbial respiration instead of biomass production, thereby supporting the microbialization of reefs. In contrast to previous studies, HMW coral and not algal exudates selected for opportunistic microbes, suggesting that a shift in the prevalent DOM composition and not the exudate type (i.e., coral vs algae) per se , may induce the rise of opportunistic microbial taxa., Importance: Dissolved organic matter (DOM) released by benthic primary producers fuels coral reef food webs. Anthropogenic stressors cause shifts from coral to algae dominance on many reefs, and resulting alterations in the DOM pool can promote opportunistic microbes and potential coral pathogens in reef water. To better understand these DOM-induced effects on bacterioplankton communities, we compared the carbohydrate composition of coral- and macroalgae-DOM and analyzed the response of bacterioplankton from an algae-dominated reef to these DOM types. In line with the proposed microbialization of reefs, coral-DOM was efficiently utilized, promoting energy transfer to higher trophic levels, whereas macroalgae-DOM likely stimulated microbial respiration over biomass production. Contrary to earlier findings, coral- and not algal-DOM selected for opportunistic microbial taxa, indicating that a change in the prevalent DOM composition, and not DOM type, may promote the rise of opportunistic microbes. Presented results may also apply to other coastal marine ecosystems undergoing benthic community shifts., Competing Interests: The authors declare no conflict of interest.

The ruminant-microorganism symbiosis is unique by providing high-quality food from fibrous materials but also contributes to the production of one of the most potent greenhouse gases-methane. Mitigating methanogenesis in ruminants has been a focus of interest in the past decades. One of the promising strategies to combat methane production is the use of feed supplements, such as seaweeds, that might mitigate methanogenesis via microbiome modulation and direct chemical inhibition. We conducted in vitro investigations of the effect of three seaweeds ( Ascophyllum nodosum , Asparagopsis taxiformis , and Fucus vesiculosus ) harvested at different locations (Iceland, Scotland, and Portugal) on methane production. We applied metataxonomics (16S rRNA gene amplicons) and metagenomics (shotgun) methods to uncover the interplay between the microbiome's taxonomical and functional states, methanogenesis rates, and seaweed supplementations. Methane concentration was reduced by A. nodosum and F. vesiculosus , both harvested in Scotland and A. taxiformis , with the greatest effect of the latter. A. taxiformis acted through the reduction of archaea-to-bacteria ratios but not eukaryotes-to-bacteria. Moreover, A. taxiformis application was accompanied by shifts in both taxonomic and functional profiles of the microbial communities, decreasing not only archaeal ratios but also abundances of methanogenesis-associated functions. Methanobrevibacter "SGMT" ( M. smithii, M. gottschalkii, M. millerae or M. thaueri ; high methane yield) to "RO" ( M. ruminantium and M. olleyae ; low methane yield) clades ratios were also decreased, indicating that A. taxiformis application favored Methanobrevibacter species that produce less methane. Most of the functions directly involved in methanogenesis were less abundant, while the abundances of the small subset of functions that participate in methane assimilation were increased., Importance: The application of A. taxiformis significantly reduced methane production in vitro . We showed that this reduction was linked to changes in microbial function profiles, the decline in the overall archaeal community counts, and shifts in ratios of Methanobrevibacter "SGMT" and "RO" clades. A. nodosum and F. vesiculosus , obtained from Scotland, also decreased methane concentration in the total gas, while the same seaweed species from Iceland did not., Competing Interests: The authors declare no conflict of interest.

We isolated and characterized the community of cultivable fungi associated with marine macroalgae present in the Magellan sub-Antarctic straits and the South Shetland Islands, Maritime Antarctica, and evaluated their production of bioactive metabolites. A total of 201 filamentous fungal isolates were obtained. The genera Antarctomyces, Pseudogymnoascus, Microdochium, Trichoderma, Cladosporium, Penicillium, Neoascochyta, Entomortierella and Linnemannia were associated with Antarctic macroalgae, with Neoascochyta paspali being the most abundant taxon. In contrast, 12 taxa representing Cadophora, Microdochium, Penicillium, Pseudogymnoascus were associated with macroalgae from the Magellan sub-Antarctic, with Penicillium dominating the assemblages. The diversity indices of the fungal communities associated with macroalgae in the two regions were similar. Among 177 fungal extracts assessed for metabolite production, 31 (17.5%) showed strong phytotoxic activity and 17 (9.6%) showed anti-Trypanosoma cruzi activity. Penicillium showed the highest phytotoxic and anti-Trypanosoma activity values. The detection of taxa in common between the polar and cold temperate zones reinforces the need for further investigations of the distribution of species in these distinct ecoregions. The detection of bioactive extracts produced particularly by Penicillium representatives reinforces the potential to obtain active molecules that can be explored as natural products or as sources of bioactive compounds with application in agriculture and biomedicine., (© 2024. The Author(s), under exclusive licence to Springer Nature Japan KK.)

Alginate lyases have countless potential for application in industries and medicine particularly as an appealing biocatalyst for the production of biofuels and bioactive oligosaccharides. Solid-state fermentation (SSF) allows improved production of enzymes and consumes less energy compared to submerged fermentation. Seaweeds can serve as the most promising biomass for the production of biochemicals. Alginate present in the seaweed can be used by alginate lyase-producing bacteria to support growth and can secrete alginate lyase. In this perspective, the current study was directed on the bioprocessing of brown seaweeds for the production of alginate lyase using marine bacterial isolate. A novel alginate-degrading marine bacterium Enterobacter tabaci RAU2C which was previously isolated in the laboratory was used for the production of alginate lyase using Sargassum swartzii as a low-cost solid substrate. Process parameters such as inoculum incubation period and moisture content were optimized for alginate lyase production. SSF resulted in 33.56 U/mL of alginate lyase under the static condition maintained with 75% moisture after 4 days. Further, the effect of different buffers, pH, and temperature on alginate lyase activity was also analyzed. An increase in alginate lyase activity was observed with an increase in moisture content from 60 to 75%. Maximum enzyme activity was perceived with phosphate buffer at pH 7 and 37 °C. Further, the residual biomass after SSF could be employed as biofertilizer for plant growth promotion based on the preliminary analysis. To our knowledge, this is the first report stating the usage of seaweed biomass as a substrate for the production of alginate lyase using solid-state fermentation., (© 2024. Institute of Microbiology, Academy of Sciences of the Czech Republic, v.v.i.)

In the marine environment, seaweeds (i.e. marine macroalgae) provide a wide range of ecological services and economic benefits. Like land plants, seaweeds do not provide these services in isolation, rather they rely on their associated microbial communities, which together with the host form the seaweed holobiont. However, there is a poor understanding of the mechanisms shaping these complex seaweed-microbe interactions, and of the evolutionary processes underlying these interactions. Here, we identify the current research challenges and opportunities in the field of seaweed holobiont biology. We argue that identifying the key microbial partners, knowing how they are recruited, and understanding their specific function and their relevance across all seaweed life history stages are among the knowledge gaps that are particularly important to address, especially in the context of the environmental challenges threatening seaweeds. We further discuss future approaches to study seaweed holobionts, and how we can apply the holobiont concept to natural or engineered seaweed ecosystems., (© 2024 The Author(s). New Phytologist © 2024 New Phytologist Foundation.)

We investigated the dynamics of feces-associated microorganisms in areas with wrack accumulation in the southeastern part of the Baltic Sea. Our study covered single-day (2021 ) and multi-day (2022) observations during the recreational season. We collected water, sand, and wrack samples and assessed the abundance of fecal indicator bacteria (FIB), as well metagenomic analysis was conducted to monitor changes in microbial composition. Based on metagenomic data we identified taxa associated with feces, sewage, and ruminant sources. Human-related fecal pollution based on genetic markers correlated with the presence of Lachnospiraceae, Prevotellaceae and Rickenellacea abundance. Higher abundance and diversity of feces-associated and ruminant-associated taxa and the presence of enteric pathogens were observed when wrack accumulated near the river outflow in 2021, suggesting a potential link with fecal pollution from the river. As a preventive measure, it is recommended to remove the wrack to reduce the risk of exposure to potential enteric pathogens if it is accumulated next to the river outflow., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Raman spectroscopy was used to study the complex interactions and morphogenesis of the green seaweed Ulva (Chlorophyta) and its associated bacteria under controlled conditions in a reductionist model system. Integrating multiple imaging techniques contributes to a more comprehensive understanding of these biological processes. Therefore, Raman spectroscopy was introduced as a non-invasive, label-free tool for examining chemical information of the tripartite community Ulva mutabilis-Roseovarius sp.-Maribacter sp. The study explored cell differentiation, cell wall protrusion, and bacterial-macroalgae interactions of intact algal thalli. Using Raman spectroscopy, the analysis of the CH x -stretching wavenumber region distinguished spatial regions in Ulva germination and cellular malformations under axenic conditions and upon inoculation with a specific bacterium in bipartite communities. The spectral information was used to guide in-depth analyses within the fingerprint region and to identify substance classes such as proteins, lipids, and polysaccharides, including evidence for ulvan found in cell wall protrusions., (© 2024 The Authors. ChemPhysChem published by Wiley-VCH GmbH.)

Two novel actinomycetal strains, designated CC-R113 T and CC-R104 T , were isolated from the tissues of two macroalgae collected on the northern Portuguese coast. Phylogenetic analyses based on the 16S rRNA gene showed that strain CT-R113 T belongs to the genus Nocardiopsis , being closely related to Nocardiopsis umidischolae 66/93 T and Nocardiopsis tropica VKM Ac-1457 T , with 98.65 and 98.39 % sequence similarity, respectively. The clade formed between the three type strains was confirmed by phylogenomic analysis. The genome of strain CT-R113 T was 7.27 Mb in size with a G+C content of 71.3 mol %, with average nucleotide identity (ANI) values of 89.59 and 90.14 % with strains 66/93 T and VKM Ac-1457 T , respectively. The major cellular fatty acids were identified as C 18 : 1  ω 9 c , iso-C 16 : 0 and anteiso-C 17 : 0 . Menaquinone 10 (MK-10) was the major respiratory quinone. Comparative analysis of 16S rRNA gene sequences showed that strain CC-R104 T belongs to the genus Rhodococcus and is most closely related to Rhodococcus pyridinivorans DSM 44555 T , with 98.24 % sequence similarity. However, phylogenomic analysis revealed that strain CC-R104 T establishes a clade with Rhodococcus artemisae DSM 45380 T , being more distant from Rhodococcus pyridinivorans DSM 44555 T . The genome of strain CC-R104 T was 5.34 Mb in size with a G+C content of 67.01 mol%. The ANI value between strains CC-R104 T and DSM 45380 T was 81.2 % and between strains CC-R104 T and DSM 44555 T was 81.5 %. The major cellular fatty acids were identified as C 18 : 1  ω 9 c , C 16 : 0 and summed feature 3. Menaquinone 8 (MK-8) was the only respiratory quinone. For both CC-R113 T and CC-R104 T , optimum growth was observed at pH 7.0, 28 °C and 0-5 % NaCl and whole-cell hydrolysates contained meso -diaminopimelic acid as the cell-wall diamino acid. On the basis of phenotypic, molecular and chemotaxonomic characteristics, strains CT-R113 T and CC-R104 T are considered to represent novel species, for which the names Nocardiopsis codii sp. nov. (type strain CT-R113 T =LMG33234 T =UCCCB172 T ) and Rhodococcus chondri sp. nov. (type strain CC-R104 T =LMG33233 T =UCCCB171 T ) are proposed.

The use of beneficial microorganisms and polysaccharides for the biocontrol of plant diseases currently represents a promising tool for the management of soil-borne pathogens. Despite advancements, enhancing the efficacy and sustainability of these biocontrol methods, particularly in complex soil environments, remains a challenge. Thus, we investigated the potential of four PGPR strains encapsulated in natural alginate extracted from a brown seaweed Bifurcaria bifurcata to evaluate its biocontrol capacities against Verticillium wilt of tomato, ensuring optimal performance through a synergistic effect and innovative bacterial release. Our research demonstrated that the application of PGPR and alginate reduced disease severity and mortality rate and increased the natural defenses of tomato. Results showed that supplying alginate or the PGPR consortium at the root level s stimulates phenylalanine ammonia-lyase activity (the key enzyme of the phenylpropanoid metabolism) and the accumulation of phenolic compounds and lignin in leaves and roots. Treatment with PGPR encapsulated in alginate beads showed the best biocontrol efficiency and was accompanied by a synergistic effect reflecting a rapid, intense, and systemic induction of defense mechanisms known for their effectiveness in inducing resistance in tomato. These promising results suggest that such bioformulations could lead to innovative agricultural practices for sustainable plant protection against pathogens., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Hydrophobins (HFBs) and cerato-platanins (CPs) are surface-active extracellular proteins produced by filamentous fungi. This study identified two HFB genes (pshyd1 and pshyd2) and one CP gene (pscp) in the marine fungus Paradendryphiella salina. The proteins PsCP, PsHYD2, and PsHYD1 had molecular weights of 12.70, 6.62, and 5.98 kDa, respectively, with isoelectric points below 7. PsHYD1 and PsHYD2 showed hydrophobicity (GRAVY score 0.462), while PsCP was hydrophilic (GRAVY score - 0.202). Stability indices indicated in-solution stability. Mass spectrometry identified 2,922 proteins, including CP but not HFB proteins. qPCR revealed differential gene expression influenced by developmental stage and substrate, with pshyd1 consistently expressed. These findings suggest P. salina's adaptation to marine ecosystems with fewer hydrophobin genes than other fungi but capable of producing surface-active proteins from seaweed carbohydrates. These proteins have potential applications in medical biocoatings, food industry foam stabilizers, and environmental bioremediation., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: As a result of the ineffectiveness of existing control methods against Verticillium dahliae, the causal agent of verticillium wilt of olive (Olea europaea; VWO), it is necessary to search for sustainable and environmentally friendly alternatives, such as bioprotection by products based on plant extracts and other naturally synthesized compounds. Therefore, present study aimed to evaluate the effects of seven natural-based commercial products on the inhibition of mycelial growth, the germination of V. dahliae conidia and microsclerotia, and disease progression in olive plants (cv. Picual). Aluminium lignosulfonate and a copper phosphonate salt (copper phosphite) were included for comparative purposes., Results: The seaweed and willow extracts and copper phosphite inhibited V. dahliae mycelial growth by more than 50% at the high doses tested. Most of the products inhibited conidial germination by up to 90% compared to the control at the high doses tested. However, none of the products showed efficacy above 50% in inhibiting microsclerotia germination. The willow extract was the most effective at reducing disease severity and progression in olive plants, with no significant differences compared to the non-inoculated negative control., Conclusion: The results of the present study suggest that the use of natural-based products (i.e. seaweed and willow extracts) is a potential sustainable alternative in an integrated VWO control strategy. © 2024 Society of Chemical Industry., (© 2024 Society of Chemical Industry.)

A Gram-stain-negative, light khaki, strictly aerobic, rod-shaped, motile via multiple flagella, and catalase- and oxidase-positive bacterium, designated as SSM4.3 T , was isolated from the seaweed of Gouqi Island in the East China Sea. The novel isolate grows at 0-5.0% NaCl concentrations (w/v) (optimum 1%), pH 5.0-9.0 (optimum pH 7.0), and 15-37 °C (optimum 30 °C). The 16S rRNA gene sequences-based phylogeny indicates that the novel marine isolate belongs to the family Rhizobiaceae and that it shared the greatest sequence similarity (98.9%) with Peteryoungia rhizophila CGMCC 1.15691 T . This classification was also supported by phylogenetic analysis using core genes. The predominant fatty acids (≥ 10%) of the strain were identified as C 18:1 ω7c/C 18:1 ω6c. Q-10 was identified as the major isoprenoid quinone, with trace levels of Q-9 present. The major polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol. The complete genome size of strain SSM4.3 T is 4.39 Mb with a DNA G+C content of 61.3%. The average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity values between the genomes of strain SSM4.3 T and its closely related representatives were 74.80-86.93%, 20.00-32.30%, and 70.30-91.52%, respectively. Phylogenetic analysis, grounded on the core genes, reveals the evolutionary relationship between SSM4.3 T and other Peteryoungia strains. Pan-genomics analysis of 8 previously classified Peteryoungia species and SSM4.3 T revealed their unique genetic features and functions. Overall, strain SSM4.3 T was considered to be a new species of the Peteryoungia genus; the name Peteryoungia algae sp. nov. has been proposed, with type strain SSM4.3 T (= LMG 32561 = MCCC 1K07170)., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The complex interactions between epiphytic bacteria and marine macroalgae are still poorly understood, with limited knowledge about their community structure, interactions, and functions. This study focuses on comparing epiphytic prokaryotes community structure between three seaweed phyla; Chlorophyta, Rhodophyta, and Heterokontophyta in an easternmost rocky intertidal site of the Mediterranean Sea. By taking a snapshot approach and simultaneously collecting seaweed samples from the same habitat, we minimize environmental variations that could affect epiphytic bacterial assembly, thereby emphasizing host specificity. Through 16S rRNA gene amplicon sequencing, we identified that the microbial community composition was more similar within the same seaweed phylum host compared to seaweed host from other phyla. Furthermore, exclusive Amplicon Sequence Variants (ASVs) were identified for each algal phyla despite sharing higher taxonomic classifications across the other phyla. Analysis of niche breadth indices uncovers distinctive affinities and potential specialization among seaweed host phyla, with 39% of all ASVs identified as phylum specialists and 13% as generalists. Using taxonomy function prediction, we observed that the taxonomic variability does not significantly impact functional redundancy, suggesting resilience to disturbance. The study concludes that epiphytic bacteria composition is connected to host taxonomy, possibly influenced by shared morphological and chemical traits among genetically related hosts, implying a potential coevolutionary relationship between specific bacteria and their host seaweeds., (© 2024. The Author(s).)

Endophytic bacteria found in marine macroalgae have been studied for their potential antimicrobial activity, consequently, they could serve as a valuable source of bioactive compounds to control pathogenic bacteria, yeasts, and fungi. Algae endophytic bacteria were isolated from Caulerpa sp., Ulva sp., Ahnfeltiopsis sp., and Chondracantus chamissoi from Yacila and Cangrejo Beaches (Piura, Peru). Antimicrobial assays against pathogenic bacteria were evaluated using cross-culture, over-plate, and volatile organic compound tests. Afterward, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of selected crude extracts were determined, also ITS molecular analysis, antifungal activity, and PCR of iturin, fengycin, and surfactin genes were performed for bacteria strains exhibiting better activity. Forty-six algae endophytic bacteria were isolated from algae. Ten strains inhibited gram-positive pathogenic bacteria (Enterococcus faecalis, Staphylococcus epidermidis, S. aureus, and Listeria monocytogenes), and 12 inhibited gram-negative bacteria (Escherichia coli and Salmonella enteric sv typhimurium). Bacteria with better activity belong to Bacillus sp., Kluyvera ascorbata, Pantoea agglomerans, Leclercia adecarboxylata, and Enterobacter sp., which only four showed antifungal activities against Candida albicans, C. tropicalis, Colletotrichium sp., Fusarium sp., Fusarium oxysporum, and Alternaria sp. Furthermore, K. ascorbata YAFE21 and Bacillus sp. YCFE4 exhibited iturin and fengycin genes. The results indicate that the algae endophytic bacteria found in this study, particularly K. ascorbata YAFE21, Bacillus sp. YCFR6, L. adecarboxylata CUFE2, Bacillus sp. YUFE8, Enterobacter sp. YAFL1, and P. agglomerans YAFL6, could be investigated as potential producers of antimicrobial compounds due to their broad activity against various microorganisms., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Macroalgae are vital reservoirs for essential epibiotic microorganisms. Among these are growth-promoting bacteria that support the growth and healthy development of their host macroalgae, and these macroalgae can be utilized in agriculture as biostimulants, offering an alternative to traditional agrochemicals. However, to date, no comparative studies have been conducted on the functional profile and bacterial diversity associated with coastal macroalgae of Peru. In this study, we employed amplicon sequencing of the V3-V4 region of 16S rRNA gene in twelve host macroalgae collected from two rocky shores in central Peru to compare their bacterial communities. The results revealed high bacterial diversity across both sites, but differences in microbial composition were noted. The phyla Bacteroidota and Pseudomonadota were predominant. The functional prediction highlighted 44 significant metabolic pathways associated with the bacterial microbiota when comparing host macroalgae. These active pathways are related to metabolism and genetic and cellular information processing. No direct association was detected between the macroalgal genera and the associated microbiota, suggesting that the bacterial community is largely influenced by their genetic functions than the taxonomic composition of their hosts. Furthermore, some species of Chlorophyta and Rhodophyta were observed to host growth-promoting bacteria, such as Maribacter sp. and Sulfitobacter sp., (© 2024. The Author(s).)

There is an enormous diversity of life forms present in the extremely intricate marine environment. The growth and development of seaweeds in this particular environment are controlled by the bacteria that settle on their surfaces and generate a diverse range of inorganic and organic chemicals. The purpose of this work was to identify epiphytic and endophytic bacterial populations associated with ten common marine macroalgae from various areas along the Mediterranean Sea coast in Alexandria. This was done to target their distribution and possible functional aspects. Examine the effects of the algal habitat on the counting and phenotypic characterization of bacteria, which involves grouping bacteria based on characteristics such as shape, colour, mucoid nature, type of Gram stain, and their ability to generate spores. Furthermore, studying the physiological traits of the isolates under exploration provides insight into the optimum environmental circumstances for bacteria associated with the formation of algae. The majority of the bacterial isolates exhibited a wide range of enzyme activities, with cellulase, alginase, and caseinase being the most prevalent, according to the data. Nevertheless, 26% of the isolates displayed amylolytic activity, while certain isolates from Miami, Eastern Harbor, and Montaza lacked catalase activity. Geographical variations with the addition of algal extract may impact on the enumeration of the bacterial population, and this might have a relationship with host phylogeny. The most significant observation was that endophytic bacteria associated with green algae increased in all sites, while those associated with red algae increased in Abu Qir and Miami sites and decreased in Eastern Harbor. At the species level, the addition of algal extract led to a ninefold increase in the estimated number of epiphytic bacteria for Cladophora pellucida in Montaza. Notably, after adding algal extract, the number of presented endophytic bacteria associated with Codium sp. increased in Abu Qir while decreasing with the same species in Montaza. In addition to having the most different varieties of algae, Abu Qir has the most different bacterial isolates., (© 2024. The Author(s).)

Background: Pyropia yezoensis a commercially important red seaweed species, is susceptible to various microorganisms infections, among which bacterial infections are the most prominent ones. Pyropia yezoensis is often affected by harmful bacterial communities under high temperatures that can lead to its degradation and economic losses. The current study aimed to explore Pyropia yezoensis-associated microbiota and further identify potential isolates, which can degrade Pyropia yezoensis under high-temperature conditions., Methods and Results: The 16S rRNA gene sequencing was used to identify the agarolytic bacterial species. The results showed that Chromohalobacter sp. strain AZ6, Pseudoalteromonas sp. strain AZ, Psychrobacter sp. strain AZ3, Vibrio sp. strain AZ, and Halomonas sp. strain AZ07 exhibited algicidal properties as these strains were more abundant at high temperature (25 °C). Among the five isolated strains, the potential isolate Halomonas sp. strain AZ07 showed high production of agarolytic enzymes, including lipase, protease, cellulase, and amylase. This study confirmed that the isolated strain could produce these four different enzymes. The strain Halomonas AZ07 was co-treated with Pyropia yezoensis cells under two different temperature environments, including 13 °C and 25 °C. The degradation of Pyropia yezoensis occurred at the optimum temperature of 25 °C and effectively degraded their cell wall, proteins, lipids, and carbohydrates., Conclusion: The successful cultivation of Pyropia yezoensis in coastal farm environments is dependent on specific temperature and environmental factors, and lower temperatures have been observed to be particularly beneficial for the survival and growth of Pyropia yezoensis. The temperature below 13 °C was confirmed to be the best niche for the symbiotic relationship of microbiota associated with Pyropia yezoensis for its growth, development, and production., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Three actinobacterial strains, KSW2-21 T , KSW2-29 T and KSW4-17 T , were isolated from dried seaweeds collected around Gwakji Beach in Jeju, Republic of Korea. Their taxonomic positions were determined based on genomic, physiological and morphological characteristics. The isolates were Gram-positive, aerobic, non-motile, rod-shaped bacteria characterized by the following chemotaxonomic features: ornithine as the cell wall diamino acid, the N -glycolyl type of murein, MK-11 as the predominant menaquinone, polar lipids including diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and four unidentified phospholipids, with anteiso-C 15 : 0 , iso-C 16 : 0 and anteiso-C 17 : 0 as the the major fatty acids. The 16S rRNA gene phylogeny showed that the novel strains formed three distinct sublines within the genus Microbacterium . Strain KSW4-17 T formed a tight cluster with the type strain of Microbacterium hydrothermale , while strains KSW2-21 T and KSW2-29 T occupied distinct positions between the type strains of M. hydrothermale and Microbacterium testaceum . Strains KSW4-17 T and KSW2-29 T showed 99.9 % rRNA gene sequence similarity to M. hydrothermale CGMCC 1.12512 T , while strain KSW2-21 T revealed 99.4 % 16S rRNA gene sequence similarity to the type strains of M. hydrothermale and M. testaceum . The genome sizes and genomic G+C contents of the three isolates ranged from 3.44 to 3.74 Mbp and from 70.3 to 70.8 mol%, respectively. The phylogenomic tree based on 92 core gene sequences exhibited similar topologies to the 16S rRNA gene phylogeny. The comparison of overall genomic relatedness indices, such as average nucleotide indentity and digital DNA-DNA hybridization, supported that the isolates represent three new species of the genus Microbacterium . Based on the results obtained here, Microbacterium algihabitans sp. nov. (type strain, KSW2-21 T =KACC 23322 T =DSM 116381 T ), Microbacterium phycohabitans sp. nov. (type strain KSW2-29 T =KACC 22350 T =NBRC 115221 T ) and Microbacterium galbum sp. nov. (type strain, KSW4-17 T =KACC 23323 T =DSM 116383 T ) are proposed.

Seaweeds are important components of marine ecosystems with emerging potential in aquaculture and as sources of biofuel, food products and pharmacological compounds. However, an increasingly recognised threat to natural and industrial seaweed populations is infection with parasitic single-celled eukaryotes from the relatively understudied oomycete lineage. Here we examine the eukaryomes of diverse brown, red and green marine macroalgae collected from polar (Baffin Island), cold-temperate (Falkland Islands) and tropical (Ascension Island) locations, with a focus on oomycete and closely related diatom taxa. Using 18S rRNA gene amplicon sequencing, we show unexpected genetic and taxonomic diversity of the eukaryomes, a strong broad-brush association between eukaryome composition and geographic location, and some evidence of association between eukaryome structure and macroalgal phylogenetic relationships (phylosymbiosis). However, the oomycete fraction of the eukaryome showed disparate patterns of diversity and structure, highlighting much weaker association with geography and no evidence of phylosymbiosis. We present several novel haplotypes of the most common oomycete Eurychasma dicksonii and report for the first time a cosmopolitan distribution and absence of host specificity of this important pathogen. This indicates rich diversity in macroalgal oomycete pathogens and highlights that these pathogens may be generalist and highly adaptable to diverse environmental conditions., (© 2024 The Author(s). Environmental Microbiology published by John Wiley & Sons Ltd.)

Pattern-triggered immunity (PTI) is an integral part of the innate immune system of many eukaryotic hosts, assisting in the defence against pathogen invasions. In plants and animals, PTI exerts a selective pressure on the microbiota that can alter community composition. However, the effect of PTI on the microbiota for non-model hosts, including seaweeds, remains unknown. Using quantitative polymerase chain reaction complemented with 16S rRNA gene and transcript amplicon sequencing, this study profiled the impact that PTI of the red seaweed Gracilaria gracilis has on its microbiota. PTI elicitation with agar oligosaccharides resulted in a significant reduction in the number of bacteria (by >75% within 72 h after treatment). However, the PTI elicitation did not cause any significant difference in the community diversity or structure. These findings demonstrated that PTI can be non-selective, and this might help to maintain a stable microbiota by uniformly reducing bacterial loads., (© 2024 The Authors. Environmental Microbiology Reports published by John Wiley & Sons Ltd.)

Ecological interactions and symbiosis between algae and fungi are ancient, widespread, and diverse with many independent origins. The heterotrophic constraint on fungal nutrition drives fungal interactions with autotrophic organisms, including algae. While ancestors of modern fungi may have evolved as parasites of algae, there remains a latent ability in algae to detect and respond to fungi through a range of symbioses that are witnessed today in the astounding diversity of lichens, associations with corticoid and polypore fungi, and endophytic associations with macroalgae. Research into algal-fungal interactions and biotechnological innovation have the potential to improve our understanding of their diversity and functions in natural systems, and to harness this knowledge to develop sustainable and novel approaches for producing food, energy, and bioproducts., Competing Interests: Declaration of Competing Interest The author declares that he has no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Coastal herbivorous fishes consume macroalgae, which is then degraded by microbes along their digestive tract. However, there is scarce genomic information about the microbiota that perform this degradation. This study explores the potential of Kyphosus gastrointestinal microbial symbionts to collaboratively degrade and ferment polysaccharides from red, green, and brown macroalgae through in silico study of carbohydrate-active enzyme and sulfatase sequences. Recovery of metagenome-assembled genomes (MAGs) from previously described Kyphosus gut metagenomes and newly sequenced bioreactor enrichments reveals differences in enzymatic capabilities between the major microbial taxa in Kyphosus guts. The most versatile of the recovered MAGs were from the Bacteroidota phylum, whose MAGs house enzyme collections able to decompose a variety of algal polysaccharides. Unique enzymes and predicted degradative capacities of genomes from the Bacillota (genus Vallitalea ) and Verrucomicrobiota (order Kiritimatiellales ) highlight the importance of metabolic contributions from multiple phyla to broaden polysaccharide degradation capabilities. Few genomes contain the required enzymes to fully degrade any complex sulfated algal polysaccharide alone. The distribution of suitable enzymes between MAGs originating from different taxa, along with the widespread detection of signal peptides in candidate enzymes, is consistent with cooperative extracellular degradation of these carbohydrates. This study leverages genomic evidence to reveal an untapped diversity at the enzyme and strain level among Kyphosus symbionts and their contributions to macroalgae decomposition. Bioreactor enrichments provide a genomic foundation for degradative and fermentative processes central to translating the knowledge gained from this system to the aquaculture and bioenergy sectors.IMPORTANCESeaweed has long been considered a promising source of sustainable biomass for bioenergy and aquaculture feed, but scalable industrial methods for decomposing terrestrial compounds can struggle to break down seaweed polysaccharides efficiently due to their unique sulfated structures. Fish of the genus Kyphosus feed on seaweed by leveraging gastrointestinal bacteria to degrade algal polysaccharides into simple sugars. This study reconstructs metagenome-assembled genomes for these gastrointestinal bacteria to enhance our understanding of herbivorous fish digestion and fermentation of algal sugars. Investigations at the gene level identify Kyphosus guts as an untapped source of seaweed-degrading enzymes ripe for further characterization. These discoveries set the stage for future work incorporating marine enzymes and microbial communities in the industrial degradation of algal polysaccharides., Competing Interests: The authors declare no conflict of interest.

Background: Endophytic fungi have an abundant sources rich source of rich bioactive molecules with pivotal pharmacological properties. Several studies have found that endophytic fungi-derived bioactive secondary metabolites have antiproliferative, anti-oxidant, and anti-inflammatory properties, but the molecular mechanism by which they induce cell cycle arrest and apoptosis pathways is unknown. This study aimed to determine the molecular mechanism underlying the anticancer property of the endophytic fungi derived active secondary metabolites on human breast cancer cells., Methods: In this study, we identified four endophytic fungi from marine seaweeds and partially screened its phytochemical properties by Chromatography-Mass Spectrometry (GC-MS) analysis. Moreover, the molecular mechanism underlying the anticancer property of these active secondary metabolites (FA, FB, FC and FE) on human breast cancer cells were examined on MCF-7 cells by TT assay, Apoptotic assay by Acridine orang/Ethidium Bromide (Dual Staining), DNA Fragmentation by DAPI Staining, reactive oxygen species (ROS) determination by DCFH-DA assay, Cell cycle analysis was conducted Flow cytometry and the apoptotic signalling pathway was evaluated by westernblot analysis. Doxorubicin was used as a positive control drug for this experiment., Results: The GC-MS analysis of ethyl acetate extract of endophytic fungi from the marine macro-algae revealed the different functional groups and bioactive secondary metabolites. From the library, we observed the FC (76%), FB (75%), FA (73%) and FE (71%) have high level of antioxidant activity which was assessed by DPPH scavenging assay. Further, we evaluated the cytotoxic potentials of these secondary metabolites on human breast cancer MCF-7 cells for 24 h and the IC 50 value were calculated (FA:28.62 ± 0.3 µg/ml, FB:49.81 ± 2.5 µg/ml, FC:139.42 ± µg/ml and FE:22.47 ± 0.5 µg/ul) along with positive control Doxorubicin 15.64 ± 0.8 µg/ml respectively by MTT assay. The molecular mechanism by which the four active compound induced apoptosis via reactive oxygen species (ROS) and cell cycle arrest in MCF-7 cells was determined H 2 DCFDA staining, DAPI staining, Acridine orange and ethidium bromide (AO/EtBr) dual staining, flowcytometry analysis with PI staining and apoptotic key regulatory proteins expression levels measured by westernblot analysis., Conclusion: Our findings, revealed the anticancer potential of endophytic fungi from marine seaweed as a valuable source of bioactive compounds with anticancer properties and underscore the significance of exploring marine-derived endophytic fungi as a promising avenue for the development of novel anticancer agents. Further investigations are necessary to isolate and characterize specific bioactive compounds responsible for these effects and to validate their therapeutic potential in preclinical and clinical settings., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Six metagenome-assembled genomes (JB008 Ts , JB007, JB015, JB003, JB004, and JB002) belonging to the order Spirochaetales were generated from seaweed samples collected from the Gulf of Mannar, India. The binned genomes JB008 Ts and JB007 shared highest 16S rRNA gene identity of 94.9 % and 92.2-93.4 %, respectively with uncultivated Spirochaetaceae family members, and < 90 % identity with Marispirochaeta aestuari JC444 T . While, the bin JB015 showed 99.1 % identity with Pleomorphochaeta naphthae SEBR 4209 T . The phylogenomic and 16S rRNA gene-based phylogenetic analysis of the binned genomes JB007 and JB008 Ts confirmed that these members belong to the family Spirochaetaceae and bins JB015, JB002, JB003, and JB004 belong to the genus Pleomorphochaeta within the family Sphaerochaetaceae. The AAI values of the binned genomes JB007 and JB008 Ts compared to other members of the Spirochaetaceae family were between 53.9- 56.8 % and 53.8-57.1 %, respectively. Furthermore, the comparison of ANI, dDDH, and POCP metrics of the binned genomes JB007 and JB008 Ts , both among themselves and with the members of Spirochaetaceae, was also below the suggested thresholds for genera delineation. Consequently, the binned genome JB008 Ts is proposed as a new genus according to the guidelines of code of nomenclature of prokaryotes described from sequence data (SeqCode) with the name Thalassospirochaeta sargassi gen. nov. sp. nov., in the family Spirochaetaceae while the bin JB007 could not be proposed as novel taxa due to low-quality estimates. The bin JB015 and its additional genomes form a distinct clade, but their taxonomic status remains ambiguous due to the absence of genomic evidence from other Pleomorphochaeta members., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier GmbH. All rights reserved.)

In mid-November 2021, there were large areas of white rot disease on cultivated Saccharina japonica in Rongcheng City, China, and diseases were undetected on Sargassum horneri and Porphyra yezoensis. The disturbance direction of bacterial community in the phycosphere after disease outbreak and the relationship with seawater nutrients remain unclear. Here, in situ studies of bacterial community in the non-diseased and diseased areas (Shawo and Dongchu islands) and seawater nutrient levels were carried out. 16S rRNA sequencing showed that the bacterial richness of the studied seaweeds increased in the diseased area. Only in S. japonica, Algitalea outcompeted abundant primary bacteria with probiotic relationships to the host of the non-diseased area, and dominated in the diseased area (17.6% of the total abundance). Nitrogen and phosphorus levels in seawater were 57.8% and 19.6% higher in the non-diseased area than those in the diseased area, respectively, and were strongly correlated with the phycosphere bacteria at the family level of S. japonica. There was no difference in potential pathogenicity between the two areas, while positive signal communications decreased, and nitrogen cycle, chemoheterotrophy, and cellulolysis increased in the diseased area compared to the non-diseased area. Overall, white rot disease caused a structural disturbance in phycosphere bacterial community of S. japonica that related to seawater nutrient levels. Enriched degraders and altered bacterial community functions may exacerbate the disease. This evaluation will provide information for white rot disease management to prevent and mitigate the occurrence of S. japonica outbreaks., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Aims: Macroalgae harbor a rich epiphytic microbiota that plays a crucial role in algal morphogenesis and defense mechanisms. This study aims to isolate epiphytic cultivable microbiota from Ulva sp. surfaces. Various culture media were employed to evaluate a wide range of cultivable microbiota. Our objective was to assess the antibacterial and biofilm-modulating activities of supernatants from isolated bacteria., Methods and Results: Sixty-nine bacterial isolates from Ulva sp. were identified based on 16S rRNA gene sequencing. Their antibacterial activity and biofilm modulation potential were screened against three target marine bacteria: 45%, mostly affiliated with Gammaproteobacteria and mainly grown on diluted R2A medium (R2Ad), showed strong antibacterial activity, while 18% had a significant impact on biofilm modulation. Molecular network analysis was carried out on four bioactive bacterial supernatants, revealing new molecules potentially responsible for their activities., Conclusion: R2Ad offered the greatest diversity and proportion of active isolates. The molecular network approach holds promise for both identifying bacterial isolates based on their molecular production and characterizing antibacterial and biofilm-modulating activities., (© The Author(s) 2024. Published by Oxford University Press on behalf of Applied Microbiology International.)

Actinomycetota, associated with macroalgae, remains one of the least explored marine niches. The secondary metabolism of Actinomycetota, the primary microbial source of compounds relevant to biotechnology, continues to drive research into the distribution, dynamics, and metabolome of these microorganisms. In this study, we employed a combination of traditional cultivation and metagenomic analysis to investigate the diversity of Actinomycetota in two native macroalgae species from the Portuguese coast. We obtained and taxonomically identified a collection of 380 strains, which were distributed across 12 orders, 15 families, and 25 genera affiliated with the Actinomycetia class, with Streptomyces making up approximately 60% of the composition. Metagenomic results revealed the presence of Actinomycetota in both Chondrus crispus and Codium tomentosum datasets, with relative abundances of 11% and 2%, respectively. This approach identified 12 orders, 16 families, and 17 genera affiliated with Actinomycetota, with minimal overlap with the cultivation results. Acidimicrobiales emerged as the dominant actinobacterial order in both macroalgae, although no strain affiliated with this taxonomic group was successfully isolated. Our findings suggest that macroalgae represent a hotspot for Actinomycetota. The synergistic use of both culture-dependent and independent approaches proved beneficial, enabling the identification and recovery of not only abundant but also rare taxonomic members., (© 2024 The Authors. Environmental Microbiology published by John Wiley & Sons Ltd.)

The microbiomes in macroalgal holobionts play vital roles in regulating macroalgal growth and ocean carbon cycling. However, the virospheres in macroalgal holobionts remain largely underexplored, representing a critical knowledge gap. Here we unveil that the holobiont of kelp (Saccharina japonica) harbors highly specific and unique epiphytic/endophytic viral species, with novelty (99.7% unknown) surpassing even extreme marine habitats (e.g. deep-sea and hadal zones), indicating that macroalgal virospheres, despite being closest to us, are among the least understood. These viruses potentially maintain microbiome equilibrium critical for kelp health via lytic-lysogenic infections and the expression of folate biosynthesis genes. In-situ kelp mesocosm cultivation and metagenomic mining revealed that kelp holobiont profoundly reshaped surrounding seawater and sediment virus-prokaryote pairings through changing surrounding environmental conditions and virus-host migrations. Some kelp epiphytic viruses could even infect sediment autochthonous bacteria after deposition. Moreover, the presence of ample viral auxiliary metabolic genes for kelp polysaccharide (e.g. laminarin) degradation underscores the underappreciated viral metabolic influence on macroalgal carbon cycling. This study provides key insights into understanding the previously overlooked ecological significance of viruses within macroalgal holobionts and the macroalgae-prokaryotes-virus tripartite relationship., (© The Author(s) 2024. Published by Oxford University Press on behalf of the International Society for Microbial Ecology.)

Different marine seaweed species have been shown to harbour specific bacterial communities, however, the extent to which vertical symbiont transmission from parents to offspring contributes to host-specificity is unclear. Here we use fluorescence and electron microscopy as well as 16S rRNA gene-based community analysis to investigate symbiont transmission in members of the three major seaweed groups (green Chlorophyta, red Rhodophyta and brown Phaeophyceae). We found seaweeds employ diverse strategies to transfer symbionts to their progeny. For instance, the green Ulva australis does not appear to have the capacity for vertical transmission. In contrast, the brown Phyllospora comosa adopts a non-selective vertical transmission. The red Delisea pulchra demonstrates weak selectivity in symbiont transmission, while the brown Hormosira banksii exhibits a strongly selective symbiont transfer. Mucilage on the gametes appears to facilitate vertical transmission and transferred bacteria have predicted properties that could support early development of the seaweeds. Previous meta-analysis has indicated that vertical transmission is rare in aquatic compared to terrestrial environments, however, our results contribute to the growing evidence that this might not be the case and that instead vertical transmission with various degrees of symbiont selection occurs in the ecologically important group of seaweeds., (© 2023 The Authors. Environmental Microbiology published by Applied Microbiology International and John Wiley & Sons Ltd.)

Background: Macroalgal epiphytic microbial communities constitute a rich resource for novel enzymes and compounds, but studies so far largely focused on tag-based microbial diversity analyses or limited metagenome sequencing of single macroalgal species., Results: We sampled epiphytic bacteria from specimens of Ulva sp. (green algae), Saccharina sp. (brown algae), Grateloupia sp. and Gelidium sp. (both red algae) together with seawater and sediment controls from a coastal reef in Weihai, China, during all seasons. Using 16S rRNA amplicon sequencing, we identified 14 core genera (consistently present on all macroalgae), and 14 dominant genera (consistently present on three of the macroalgae). Core genera represented ~ 0.7% of all genera, yet accounted for on average 51.1% of the bacterial abundances. Plate cultivation from all samples yielded 5,527 strains (macroalgae: 4,426) representing 1,235 species (685 potentially novel). Sequencing of selected strains yielded 820 non-redundant draft genomes (506 potentially novel), and sequencing of 23 sampled metagenomes yielded 1,619 metagenome-assembled genomes (MAGs), representing further 1,183 non-redundant genomes. 230 isolates and 153 genomes were obtained from the 28 core/dominant genera. We analyzed the genomic potential of phycosphere bacteria to degrade algal polysaccharides and to produce bioactive secondary metabolites. We predicted 4,451 polysaccharide utilization loci (PULs) and 8,810 biosynthetic gene clusters (BGCs). These were particularly prevalent in core/dominant genera., Conclusions: Our metabolic annotations and analyses of MAGs and genomes provide new insights into novel species of phycosphere bacteria and their ecological niches for an improved understanding of the macroalgal phycosphere microbiome. Video Abstract., (© 2023. The Author(s).)

Gram-positive, aerobic, motile, rod-shaped, mesophilic epiphytic bacterium Planomicrobium okeanokoites was isolated from the surface of endemic species Himantothallus grandifolius in Larsemann Hills, Eastern Antarctica. The diversity of epiphytic bacterial communities living on marine algae remains primarily unexplored; virtually no reports from Antarctic seaweeds. The present study used morpho-molecular approaches for the macroalgae and epiphytic bacterium characterization. Phylogenetic analysis was performed using mitochondrial genome encoded COX1 gene; chloroplast genome encodes rbcL; nuclear genome encoded large subunit ribosomal RNA gene (LSU rRNA) for Himantothallus grandifolius and ribosomal encoded 16S rRNA for Planomicrobium okeanokoites. Morphological and molecular data revealed that the isolate is identified as Himantothallus grandifolius, which belongs to Family Desmarestiaceae of Order Desmarestiales in Class Phaeophyceae showing 99.8% similarity to the sequences of Himantothallus grandifolius, from King George Island, Antarctica (HE866853). The isolated bacterial strain was identified on the basis of chemotaxonomic, morpho-phylogenetic, and biochemical assays. A phylogenetic study based on 16S rRNA gene sequences revealed that the epiphytic bacterial strain SLA-357 was closest related to the Planomicrobium okeanokoites showing 98.7% sequence similarity. The study revealed the first report of this species from the Southern Hemisphere to date. Also, there has been no report regarding the association between the Planomicrobium okeanokoites and Himantothallus grandifolius; however, there are some reports on this bacterium isolated from sediments, soils, and lakes from Northern Hemisphere. This study may open a gateway for further research to know about the mode of interactions and how they affect the physiology and metabolism of each other., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Saini et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

The effects of increased UV-B radiation on macroalgae have been widely studied, but knowledge concerning the response of communities of algal epiphytic bacteria to increased UV-B radiation and differences between male and female algae is still lacking. Via 16S rDNA high-throughput sequencing technology, changes in the epiphytic bacterial communities on male and female S. thunbergii under increased UV-B radiation were studied in the lab. Under different UV-B radiation intensities, although the α diversity and community composition of epiphytic bacteria changed little, the β diversity indicated that the community structure of bacteria on S. thunbergii was obviously clustered, and the relative abundance of dominant bacteria and indicator species changed considerably. There were unique bacteria in each experimental group, and the bacteria whose abundance obviously changed were members of groups related to environmental resistance or adaptability. The variation in the abundance of epiphytic bacteria was different in male and female S. thunbergii, and the bacteria whose abundance greatly changed were mainly related to algal growth and metabolism. The abundance of genes with predicted functions related to metabolism, genetic information processing, environmental adaptation and infectious diseases changed with increased UV-B radiation, and those variations differed between epiphytic bacteria on male and female S. thunbergii. This study found that the algal epiphytic bacteria were influenced by the increase in UV-B radiation and underwent certain adaptations through adjustments to community structure and function, and this response was also affected by the sex of the macroalgae. These results are expected to serve as experimental basis and provide reference for further understanding of the response of algae epiphytic bacteria to enhanced UV-B radiation caused by the thinning of the ozone layer and the resulting changes in the relationship between algae and bacteria, which may change the community of the marine ecosystem and affect important marine ecological process., (© 2023. The Author(s).)

The marine green macroalga Ulva (Chlorophyta, Ulvales), also known as sea lettuce, coexists with a diverse microbiome. Many Ulva species proliferate in nature and form green algal blooms ("green tides"), which can occur when nutrient-rich wastewater from agricultural or densely populated areas is flushed into the sea. Bacteria are necessary for the adhesion of Ulva to its substrate, its growth, and the development of its blade morphology. In the absence of certain bacteria, Ulva mutabilis develops into a callus-like morphotype. However, with the addition of the necessary marine bacteria, the entire morphogenesis can be restored. Surprisingly, just two bacteria isolated from U. mutabilis are sufficient for inducing morphogenesis and establishing the reductionist system of a tripartite community. While one bacterial strain causes algal blade cell division, another causes the differentiation of basal cells into a rhizoid and supports cell wall formation because of a low concentration of the morphogen thallusin (below 10 -10 mol/L). This review focuses on the research conducted on this topic since 2015, discusses how U. mutabilis has developed into a model organism in chemical ecology, and explores the questions that have already been addressed and the perspectives that a reductionist model system allows. In particular, the field of systems biology will achieve a comprehensive, quantitative understanding of the dynamic interactions between Ulva and its associated bacteria to better predict the behavior of the system as a whole. The reductionist approach has enabled the study of the bacteria-induced morphogenesis of Ulva. Specific questions regarding the optimization of cultivation conditions as well as the yield of raw materials for the food and animal feed industries can be answered in the laboratory and through applied science. Genome sequencing, the improvement of genetic engineering tools, and the first promising attempts to leverage macroalgae-microbe interactions in aquaculture make this model organism, which has a comparatively short parthenogenetic life cycle, attractive for both fundamental and applied research. The reviewed research paves the way for the synthetic biology of macroalgae-associated microbiomes in sustainable aquacultures., Competing Interests: Declaration of interest None., (Copyright © 2022 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Since the report of the antibiotic with anticancer properties, scientists have been focusing to isolate and characterize novel anti-microbial natural products possessing anticancer activities. The current study describes the production of seaweed-associated heterotrophic Bacillus altitudinis MTCC13046 with potential anticancer properties. The bacterium was screened for its capacity to diminish the cell proliferation of the human hepatocellular adenocarcinoma (HepG2) cell line, without upsetting the normal cells. The bacterial extract showed anticancer properties in a dose-reactive form against HepG2 (IC 50 , half maximal inhibitory concentration ~ 29.5 µg/ml) on tetrazolium bromide analysis with less significant cytotoxicity on common fibroblast (HDF) cells (IC 50  ~ 77 µg/ml). The potential antioxidant ability of the organic extract of B. altitudinis MTCC13046 (IC 90 133 µg/ml) could corroborate its capacity to attenuate the pathophysiology leading to carcinogenesis. The results of the apoptosis assay showed that the crude extracts of B. altitudinis maintained 68% viability in normal cells compared to 11% in the cancer cells (IC 50 76.9 µg/ml). According to the findings, B. altitudinis MTCC13046 could be used to develop prospective anticancer agents., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Intertidal macroalgae face periodic water loss and rehydration caused by daily tidal changes. However, the effect of water loss stress on algal epiphytic bacteria has not yet been reported. In this study, the effects of water loss stress on the epiphytic bacteria community of Sargassum thunbergii were analyzed, and the different responses of epiphytic bacteria to water loss stress were compared between male and female algae. The results showed that after water loss stress, the diversity of the epiphytic bacterial community of S. thunbergii first decreased and then increased. Among the dominant taxa, the abundance of Cyanobacteria decreased significantly, whereas the abundance of Portibacter and Aquimarina first increased and then decreased. Additionally, the indicator species and the abundance of predicted functional genes related to carbon, nitrogen, and sulfur metabolism both changed significantly. More importantly, when the epiphytic bacteria were analyzed separately according to the algal sex, the changes in algal epiphytic bacterial community structure and indicator species were more significant, and there were sexual differences. Therefore, it was concluded that water loss stress has a significant effect on the community structure and function of the epiphytic bacteria on S. thunbergii . Meanwhile, the epiphytic bacteria community of two sexes of S. thunbergii differed in the response to water loss stress. IMPORTANCE Periodic water loss caused by the tide is an important environmental factor that is faced by intertidal macroalgae, but the impact of periodic water loss on the epiphytic bacterial communities associated with macroalgae is still unknown. Through this study, we found that the diversity, the relative abundance of dominant taxa, the indicator species, and the abundance of the predicted functional genes in the epiphytic bacteria on S. thunbergii changed with the time of water loss. Moreover, male and female S. thunbergii exhibited different responses to water loss stress. This study not only paves the way for the delineation of the interactions between S. thunbergii and its epiphytic bacteria but also provides new insights for the mechanisms of the adaptation and evolution of macroalgae in the intertidal zone.

Seaweed-associated bacterial symbionts are sources of potential pharmacological properties. The present study resulted in the culture-dependent isolation of bioactive heterotrophs belonging to the bacterial phylum Firmicutes, which were dominated more than 30% of the 127 cultivable isolates, amongst which 23 of them showed potential antimicrobial activities against a wide range of pathogens. The symbionts isolated from the seaweed Sargassum wightii showed significant bioactivity. Those were characterized as Bacillus safensis MTCC13040, B. valismortis MTCC13041, B. velezensis MTCC13044, B. methylotrophicus MTCC13042, Oceanobacillus profundus MTCC13045, B. tequilensis MTCC13043, and B. altitudinis MTCC13046. The organic extracts of the studied isolates showed potential antimicrobial properties against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococci (minimum inhibitory concentration 6·25-12·5 μg ml -1 ). The organic extract of B. altitudinis MTCC13046 displayed significantly greater radical quenching ability (IC 90 133 μg ml -1 , P < 0·05) other than attenuating hydroxymethyl glutaryl coenzyme A reductase (IC 90 10·21 μg ml -1 , P < 0·05) and angiotensin-converting enzyme-1 (IC 90 498 μg ml -1 , P < 0·05) relative to other studied heterotrophs. The organic extract of B. tequilensis MTCC13043 displayed significantly greater attenuation potential against pro-inflammatory 5-lipooxygenase (IC 90 5·94 μg ml -1 , P < 0·05) and dipeptidyl peptidase-4 (IC 90 271 μg ml -1 , P < 0·05). The seaweed-associated B. altitudinis MTCC13046 and B. tequilensis MTCC13043 could be used to develop promising pharmacological leads., (© 2022 Society for Applied Microbiology.)

Chemical mediators are key compounds for controlling symbiotic interactions in the environment. Here, we disclose a fully stereoselective total synthesis of the algae differentiation factor (-)-thallusin that utilizes sophisticated 6-endo-cyclization chemistry and effective late-stage sp 2 -sp 2 -couplings using non-toxic reagents. An EC 50 of 4.8 pM was determined by quantitative phenotype profiling in the green seaweed Ulva mutabilis (Chlorophyte), underscoring this potent mediator's enormous, pan-species bioactivity produced by symbiotic bacteria. SAR investigations indicate that (-)-thallusin triggers at least two different pathways in Ulva that may be separated by chemical editing of the mediator compound structure., (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Marine macroalgae are important ecosystem engineers in marine coastal habitats. Macroalgae can be negatively impacted through excessive colonization by harmful bacteria, fungi, microalgae, and macro-colonisers and thus employ a range of chemical compounds to minimize such colonization. Recent research suggests that environmental pH conditions potentially impact the functionality of such chemical compounds. Here we predict if and how naturally fluctuating pH conditions and future conditions caused by ocean acidification will affect macroalgal (antifouling) compounds and thereby potentially alter the chemical defence mediated by these compounds. We defined the relevant ecological pH range, analysed and scored the pH-sensitivity of compounds with antifouling functions based on their modelled chemical properties before assessing their distribution across the phylogenetic macroalgal groups, and the proportion of sensitive compounds for each investigated function. For some key compounds, we also predicted in detail how the associated ecological function may develop across the pH range. The majority of compounds were unaffected by pH, but compounds containing phenolic and amine groups were found to be particularly sensitive to pH. Future pH changes due to predicted average open ocean acidification pH were found to have little effect. Compounds from Rhodophyta were mainly pH-stable. However, key algal species amongst Phaeophyceae and Chlorophyta were found to rely on highly pH-sensitive compounds for their chemical defence against harmful bacteria, microalgae, fungi, and biofouling by macro-organisms. All quorum sensing disruptive compounds were found the be unaffected by pH, but the other ecological functions were all conveyed in part by pH-sensitive compounds. For some ecological keystone species, all of their compounds mediating defence functions were found to be pH-sensitive based on our calculations, which may not only affect the health and fitness of the host alga resulting in host breakdown but also alter the associated ecological interactions of the macroalgal holobiont with micro and macrocolonisers, eventually causing ecosystem restructuring and the functions (e.g. habitat provision) provided by macroalgal hosts. Our study investigates a question of fundamental importance because environments with fluctuating or changing pH are common and apply not only to coastal marine habitats and estuaries but also to freshwater environments or terrestrial systems that are subject to acid rain. Hence, whilst warranting experimental validation, this investigation with macroalgae as model organisms can serve as a basis for future investigations in other aquatic or even terrestrial systems., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Emergence of multidrug-resistant microorganisms and requirements for novel antimicrobial compounds necessitate exploring newer habitats to develop potential bioactive leads. Culture-contingent analysis of heterotrophic bacterial flora from the seaweeds led to the isolation of bioactive strains possessing potential antibacterial properties against wide-ranging clinical pathogens viz., methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus faecalis (VREfs). Seven of the most active strains belonging to the phylum Firmicutes isolated from a brown seaweed (Phaeophyceae) Sargassum wightii exhibited spot-over-lawn assay guided inhibition zone of larger than 30 mm. Integrated phenotypic and genotypic studies have led to the characterization of the seaweed-associated bacteria particularly belonging to the phylum Firmicutes. The organic extracts of the studied bacteria exhibited promising antibacterial properties against MRSA and VREfs with minimum inhibitory concentration ranging between 6.25 and 12.50 μg/mL. Time-kill kinetic profiles of those bacteria displayed rapid bactericidal activity against both E. coli and MRSA, showing a ≥ 3log 10 reduction in viable cell count than the initial. Among the studied bioactive Bacillus spp, B. tequilensis MTCC13043 and B. altiitudinis MTCC13046 were found to possess functional polyketide synthase (pks) gene (MW027664 and MW027660) that could be amplified. The outcome of amplified genes encrypting for polyketide synthase in conjunction with antibacterial activities unveiled the broad-spectrum antimicrobial activities of the marine heterotrophic Firmicutes, which could be further used against the emergent problem of antibiotic-resistant bacterial pathogens., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Seaweed endophytic (algicolous) fungi are talented producers of bioactive natural products. We have previously isolated two strains of the endophytic fungus, Pyrenochaetopsis sp. FVE-001 and FVE-087, from the thalli of the brown alga Fucus vesiculosus . Initial chemical studies yielded four new decalinoylspirotetramic acid derivatives with antimelanoma activity, namely pyrenosetins A-C ( 1 - 3 ) from Pyrenochaetopsis sp. strain FVE-001, and pyrenosetin D ( 4 ) from strain FVE-087. In this study, we applied a comparative metabolomics study employing HRMS/MS based feature-based molecular networking (FB MN) on both Pyrenochaetopsis strains. A higher chemical capacity in production of decalin derivatives was observed in Pyrenochaetopsis sp. FVE-087. Notably, several decalins showed different retention times despite the same MS data and MS/MS fragmentation pattern with the previously isolated pyrenosetins, indicating they may be their stereoisomers. FB MN-based targeted isolation studies coupled with antimelanoma activity testing on the strain FVE-087 afforded two new stereoisomers, pyrenosetins E ( 5 ) and F ( 6 ). Extensive NMR spectroscopy including DFT computational studies, HR-ESIMS, and Mosher's ester method were used in the structure elucidation of compounds 5 and 6 . The 3' R ,5' R stereochemistry determined for compound 6 was identical to that previously reported for pyrenosetin C ( 3 ), whose stereochemistry was revised as 3' S ,5' R in this study. Pyrenosetin E ( 5 ) inhibited the growth of human malignant melanoma cells (A-375) with an IC 50 value of 40.9 μM, while 6 was inactive. This study points out significant variations in the chemical repertoire of two closely related fungal strains and the versatility of FB MN in identification and targeted isolation of stereoisomers. It also confirms that the little-known fungal genus Pyrenochaetopsis is a prolific source of complex decalinoylspirotetramic acid derivatives.

Appearance of drug-resistant microorganisms prompted researchers to unravel new environments for development of novel antimicrobial agents. Culture-supported analysis of heterotrophic bacteria associated with seaweeds yielded 152 strains, in that larger share of the isolates was embodied by Bacillus atrophaeus SHB2097 (54%), B. velezensis SHB2098 (24%), B. subtilis SHB2099 (12%), and B. amyloliquefaciens SHB20910 (10%). One of the most active strains characterized as B. atrophaeus SHB2097 (MW821482) with an inhibition zone more than 30 mm on spot-over-lawn experiment, was isolated from a seaweed Sargassum wightii, was selected for bioprospecting studies. Significant antibacterial potential was displayed by bacterial organic extract against vancomycin-resistant Enterococcus faecalis, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Klebsiella pneumonia with minimum inhibitory concentration 6.25 µg/mL and comparable to the antibiotics ampicillin and chloramphenicol. The genes of type 1 pks (MZ222383, 700 bp) and hybrid nrps/pks (MZ222389, 1000-1400 bp) of B. atrophaeus MW821482 could be amplified. The bacterium displayed susceptibility to the commercially available antibiotic agents, and was negative for the pore-forming non-hemolytic hemolysin BL (hbl) and enterotoxin (nhe) genes, and therefore, was not pathogenic. The bacterium was found to possess genes (1000-1400 bp) involved in the biosynthesis of siderophore-class of compounds (MZ222387 and MZ222388) that showed 99% of similarity in BLAST search, and showed production of siderophore. Noteworthy antibacterial activities against clinically important pathogenic bacteria in conjunction with occurrence of genes coding for antimicrobial metabolites inferred that the marine heterotrophic bacterium B. atrophaeus SHB2097 could be used for the development of antibacterial agents against the emerging antibiotic resistance., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In the context of global warming, this study aimed to assess the effect of temperature and irradiance on the macroalgal Taonia atomaria holobiont dynamics. We developed an experimental set-up using aquaria supplied by natural seawater with three temperatures combined with three irradiances. The holobiont response was monitored over 14 days using a multi-omics approach coupling algal surface metabolomics and metabarcoding. Both temperature and irradiance appeared to shape the microbiota and the surface metabolome, but with a distinct temporality. Epibacterial community first changed according to temperature, and later in relation to irradiance, while the opposite occurred for the surface metabolome. An increased temperature revealed a decreasing richness of the epiphytic community together with an increase of several bacterial taxa. Irradiance changes appeared to quickly impact surface metabolites production linked with the algal host photosynthesis (e.g. mannitol, fucoxanthin, dimethylsulfoniopropionate), which was hypothesized to explain modifications of the structure of the epiphytic community. Algal host may also directly adapt its surface metabolome to changing temperature with time (e.g. lipids content) and also in response to changing microbiota (e.g. chemical defences). Finally, this study brought new insights highlighting complex direct and indirect responses of seaweeds and their associated microbiota under changing environments., (© 2021 Society for Applied Microbiology and John Wiley & Sons Ltd.)

The ocean represents the largest biome on earth; however, we have only begun to understand the diversity and function of the marine microbial inhabitants and their interactions with macroalgal species. Macroalgae play an integral role in overall ocean biome health and serve both as major primary producers and foundation species in the ecosystem. Previous studies have been limited, focusing on the microbiome of a single algal species or its interaction with selected microbes. This project aimed to understand overall biodiversity of microbial communities associated with five common macroalgal species and to determine the drivers of these communities at 'Ewa Beach, O'ahu, HI. Representative species of Chlorophyta (green), Ochrophyta (brown), and Rhodophyta (red) algae, each species having various levels of calcification, thallus complexity, and status as native or invasive species, were collected from an intertidal bench in May 2019. A portion of the V3-V4 variable region of the small-subunit rRNA gene was amplified for high-throughput sequencing using universal bacterial primers to elucidate the core and variable algal microbiome. Significant differences in bacterial community composition were only partially explained by host species, whether the host was native or invasive, and thallus complexity. Macroalgal phylum explained the most variation in associated microbial communities at 'Ewa Beach. This study advances our understanding of microbial-macroalgal interactions and their connectivity by producing insight into factors that influence the community structure of macroalga-associated microbiota. IMPORTANCE Generally, most eukaryotic organisms form relationships with microbes that are important in mediating host organismal health. Macroalgae are a diverse group of photosynthetic eukaryotic organisms that serve as primary producers and foundational species in many ecosystems. However, little is known about their microbial counterparts across a wide range of macroalgal morphologies, phylogenies, and calcification levels. Thus, to further understand the factors involved in bacterial community composition associated with macroalgal species at one point in time, representative samples were collected across phyla. Here, we show that both host macroalga phyla and morphology influenced the associated microbial community. Additionally, we show that the invasive species Avrainvillea lacerata does not have a unique microbial community on this intertidal bench, further supporting the idea that host phylum strongly influences microbial community composition.

The rise in antibiotic-resistant bacterial strains prompting nosocomial infections drives the search for new bioactive substances of promising antibacterial properties. The surfaces of seaweeds are rich in heterotrophic bacteria with prospective antimicrobial substances. This study aimed to isolate antibacterial leads from a seaweed-associated bacterium. Heterotrophic Bacillus amyloliquefaciens MTCC 12716 associated with the seaweed Hypnea valentiae, was isolated and screened for antimicrobial properties against drug-resistant pathogens. The bacterial crude extract was purified and three novel amicoumacin-class of isocoumarin analogues, 11'-butyl acetate amicoumacin C (amylomacin A), 4'-hydroxy-11'-methoxyethyl carboxylate amicoumacin C (amylomacin B) and 11'-butyl amicoumacin C (amylomacin C) were isolated to homogeneity. The studied amylomacins possessed potential activities against Pseudomonas aeruginosa, vancomycin-resistant Enterococcus faecalis, Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus, and Shigella flexneri with a range of minimum inhibitory concentration values from 0.78 to 3.12 µg/mL, although standard antibiotics ampicillin and chloramphenicol were active at 6.25-25 µg/mL. Noticeably, the amylomacin compound encompassing 4'-hydroxy-11'-methoxyethyl carboxylate amicoumacin C functionality (amylomacin B), displayed considerably greater antagonistic activities against methicillin-resistant S. aureus, vancomycin-resistant E. faecalis, Vibrio parahaemolyticus, Escherichia coli, and K. pneumoniae (minimum inhibitory concentration 0.78 μg/mL) compared to the positive controls and other amylomacin analogues. Antimicrobial properties of the amylomacins, coupled with the presence of polyketide synthase-I/non-ribosomal peptide synthetase hybrid gene attributed the bacterium as a promising source of antimicrobial compounds with pharmaceutical and biotechnological applications., (© 2021. The Author(s), under exclusive licence to Springer Nature B.V.)

Infectious diseases affecting habitat-forming species can have significant impacts on population dynamics and alter the structure and functioning of marine ecosystems. Recently, a fungal infection was described as the causative agent of necrotic lesions on the stipe of the forest-forming macroalga Phyllospora comosa, a disease named "stipe rot" (SR). Here, we developed a quantitative PCR (qPCR) method for rapid detection and quantification of this pathogen, which was applied to evaluate the level of SR infection in eight P. comosa populations spanning the entire latitudinal distribution of this species along southeastern Australia. We also investigated the relationship between the abundance and prevalence of Stipe Rot Fungus (SRF) and potential host chemical defenses as well as its relationship with morphological and ecophysiological traits of P. comosa. qPCR estimates of SRF abundance reflected the levels of infection estimated by visual assessment, with higher numbers of SRF copies being observed in individuals showing high or intermediate levels of visual symptoms of SR. Concordance of conventional PCR and visual assessments was 92 and 94%, respectively, compared to qPCR detection. SRF prevalence was positively related to fucoxanthin content and herbivory, but not significant related to other traits measured (phlorotannin content, total length, thallus diameter, stipe width, number of branches, frond width, fouling, bleaching, gender, and photosynthetic efficiency). These results provide confidence for previous reports of this disease based upon visual assessments only, contribute to the development of monitoring and conservation strategies for safeguarding P. comosa forests, and generate insights into potential factors influencing host-pathogen interactions in this system., (© 2021 Phycological Society of America.)

Aim: To explore seaweed-associated bacteria as prospective producers of bioactive material with antibacterial properties. Materials & methods: 143 bacterial species were isolated from the surface of 15 New Zealand marine macroalgae. Bacterial extracts obtained using dimethyl sulfoxide and ethyl acetate were screened for antagonistic activities against three antimicrobial susceptibility indicators: Kocuria rhizophila , Staphylococcus epidermidis and Escherichia coli , using well-diffusion method. For selected species, minimum inhibitory concentration was determined, followed by a phylogenetic identification based on 16S rRNA gene sequences. Results: Among all bacteria screened, seven that belonged to the genera Vibrio, Pseudoalteromonas, Psychromonas  and Cobetia , showed antagonistic activity against all three indicators. Conclusion: Seaweed-associated bacteria produce bioactive compounds with antimicrobial potential and possible biomedical application in aquatic habitats.

Bacillus velezensis MTCC 10456, is a marine mesophilic heterotrophic bacterium, isolated from edible red seaweed, Laurenciae papillosa, with a potential for plant growth promotion and biocontrol activity. We report the genome sequence analysis of strain MTCC 10456, which has a genome size of 4.19 Mb with an average G + C content of 45.9%, 4077 coding sequences and 94 RNAs. Comparative genome analysis of MTCC 10456 with 76 other land plant-based strains with complete information on the source of their isolation, was carried out. This study provided evidence that multiple gene clusters that contributed to the seaweed colonization, growth promotion, immunity and hyperosmotic stress tolerance are conserved in different B. velezensis strains. A unique methyltransferase gene that can cause global alterations in DNA methylation patterns affecting gene expression and regulation of transcription in MTCC 10456 genome was identified. The genome provides insights into multiple gene clusters encoding antagonistic metabolites, such as non-ribosomal peptide synthetases (NRPSs) and polyketide synthetases (PKSs), unidentified metabolites and genes for antimicrobial resistance. Overall, findings from this study indicate the application of B. velezensis MTCC 10456 in the aquaculture industry as a biocontrol agent and may also contribute in understanding the ecological adaptations of plant-associated B. velezensis strains in different habitats., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.)

Members of the genus Malassezia are known to be opportunistic pathogens responsible for causing skin disorders such as seborrheic dermatitis or dandruff, pityriasis versicolor, folliculitis, atopic dermatitis, and psoriasis. Due to the side effects caused by prolonged use of current topical antifungal agents, development of an alternative treatment is necessary. Fermentative production of antimicrobial metabolites from Bacillus amyloliquefaciens MTCC 10456 was carried out, and their antagonistic activity against Malassezia furfur and Malassezia globosa was evaluated. The antifungal metabolites were isolated by acid precipitation, and bioassay-guided simultaneous separation of the antimicrobial compounds was done by reversed-phase high-performance liquid chromatography (RP-HPLC). The fraction which demonstrated antifungal activity consisted of bacilysin, homologues of bacillomycin D, and members of the macrolactin family. The presence of bacilysin was detected using specific inhibitor assays and homologues of bacillomycin D, and macrolactins were identified using liquid chromatography/high-resolution electrospray ionization-mass spectrometry (LC/HRESI-MS/MS) analysis. Synergism among the identified compounds was observed which enhanced the antagonistic activity against Malassezia spp. To our knowledge, this is the first study to report the co-production and separation of members of macrolactin antibiotics, lipopeptides such as bacillomycin D and dipeptide antibiotic bacilysin, by any Bacillus strain from marine environment. Activity of individual compounds against Malassezia has been reported which may facilitate their application in the field of dermatology and in cosmetic products., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.)

The therapeutic potential of Sargassum siliquosum grown in Australian tropical waters was tested in a rat model of metabolic syndrome. Forty-eight male Wistar rats were divided into four groups of 12 rats and each group was fed a different diet for 16 weeks: corn starch diet (C); high-carbohydrate, high-fat diet (H) containing fructose, sucrose, saturated and trans fats; and C or H diets with 5% S. siliquosum mixed into the food from weeks 9 to 16 (CS and HS). Obesity, hypertension, dyslipidaemia, impaired glucose tolerance, fatty liver and left ventricular fibrosis developed in H rats. In HS rats, S. siliquosum decreased body weight (H, 547 ± 14; HS, 490 ± 16 g), fat mass (H, 248 ± 27; HS, 193 ± 19 g), abdominal fat deposition and liver fat vacuole size but did not reverse cardiovascular and liver effects. H rats showed marked changes in gut microbiota compared to C rats, while S. siliquosum supplementation increased gut microbiota belonging to the family Muribaculaceae . This selective increase in gut microbiota likely complements the prebiotic actions of the alginates. Thus, S. siliquosum may be a useful dietary additive to decrease abdominal and liver fat deposition.

Marine fungi and, particularly, endophytic species have been recognised as one of the most prolific sources of structurally new and diverse bioactive secondary metabolites with multiple biotechnological applications. Despite the increasing number of bioprospecting studies, very few have already evaluated the cosmeceutical potential of marine fungal compounds. Thus, this study focused on a frequent seaweed in the Portuguese coast, Halopteris scoparia, to identify the endophytic marine fungi associated with this host, and assess their ability to biosynthesise secondary metabolites with antioxidative, enzymatic inhibitory (hyaluronidase, collagenase, elastase and tyrosinase), anti-inflammatory, photoprotective, and antimicrobial (Cutibacterium acnes, Staphylococcus epidermidis and Malassezia furfur) activities. The results revealed eight fungal taxa included in the Ascomycota, and in the most representative taxonomic classes in marine ecosystems (Eurotiomycetes, Sordariomycetes and Dothideomycetes). These fungi were reported for the first time in Portugal and in association with H. scoparia, as far as it is known. The screening analyses showed that most of these endophytic fungi were producers of compounds with relevant biological activities, though those biosynthesised by Penicillium sect. Exilicaulis and Aspergillus chevalieri proved to be the most promising ones for being further exploited by dermocosmetic industry. The chemical analysis of the crude extract from an isolate of A. chevalieri revealed the presence of two bioactive compounds, echinulin and neoechinulin A, which might explain the high antioxidant and UV photoprotective capacities exhibited by the extract. These noteworthy results emphasised the importance of screening the secondary metabolites produced by these marine endophytic fungal strains for other potential bioactivities, and the relevance of investing more efforts in understanding the ecology of halo/osmotolerant fungi., Competing Interests: The authors have declared that no competing interests exist.