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Microbial mats are stratified communities often dominated by unicellular and filamentous phototrophs within an exopolymer matrix. It is challenging to quantify the dynamic responses of community members in situ as they experience steep gradients and rapid fluctuations of light. To address this, we developed a binary consortium using two representative isolates from hot spring mats: the unicellular oxygenic phototrophic cyanobacterium Synechococcus OS-B' (Syn OS-B') and the filamentous anoxygenic phototroph Chloroflexus MS-CIW-1 (Chfl MS-1). We quantified the motility of individual cells and entire colonies and demonstrated that Chfl MS-1 formed bundles of filaments that moved in all directions with no directional bias to light. Syn OS-B' was slightly less motile but exhibited positive phototaxis. This binary consortium displayed cooperative behavior by moving further than either species alone and formed ordered arrays where both species aligned with the light source. No cooperative motility was observed when a nonmotile pilB mutant of Syn OS-B' was used instead of Syn OS-B'. The binary consortium also produced more adherent biofilm than individual species, consistent with the close interspecies association revealed by electron microscopy. We propose that cyanobacteria and Chloroflexota cooperate in forming natural microbial mats by colonizing new niches and building robust biofilms., Competing Interests: Competing interests statement:The authors declare no competing interest.

Aerobic and anaerobic organisms and their functions are spatially or temporally decoupled at scales ranging from individual cells to ecosystems and from minutes to hours. This is due to competition for energy substrates and/or biochemical incompatibility with oxygen (O 2 ). Here we report a chemolithotrophic Aquificales bacterium, Hydrogenobacter, isolated from a circumneutral hot spring in Yellowstone National Park (YNP) capable of simultaneous aerobic and anaerobic respiration when provided with hydrogen (H 2 ), elemental sulfur (S 0 ), and O 2 . Cultivation experiments demonstrated that simultaneous aerobic and anaerobic respiration enhanced growth rates and final cell concentrations when compared to those grown aerobically or anaerobically. Consumption of O 2 measured via gas chromatography and detection of transcripts for proteins involved in S 0 and O 2 reduction in H 2 /S 0 /O 2 -grown cultures confirmed co-occurring aerobic and anaerobic metabolism. This aerobic, S 0 -reducing metabolism is suggested to provide a competitive advantage in environments where O 2 availability is low and variable. Genomic data indicating the prevalence of proteins allowing for this hybrid form of energy metabolism among bacteria and archaea suggest it to be widespread but previously overlooked due to rapid, O 2 -dependent abiotic oxidation of produced sulfide. These observations challenge existing paradigms of strict delineations between aerobic and anaerobic metabolism., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Terrestrial geothermal springs, reminiscent of early Earth conditions, host diverse and abundant populations of Archaea. In this study, we reconstructed 2,949 metagenome-assembled genomes (MAGs) from 152 metagenomes collected over six years from 48 geothermal springs in Tengchong, China. Among these MAGs, 1,431 (49%) were classified as high-quality, while 1,518 (51%) were considered as medium-quality. Phylogenomic analysis revealed that these MAGs spanned 12 phyla, 27 classes, 67 orders, 147 families, 265 genera, and 475 species. Notably, 575 (19%) MAGs represented new taxa at various taxonomic levels, and 2,075 (70%) lacked nomenclature and effective descriptions. The most abundant phyla of archaeal genomes were Thermoproteota, Thermoplasmatota, and Micrarchaeota. The DRTY, ZMQ, and ZZQ geothermal springs were predominated by Archaea, particularly by Thermoproteia and Thermoplasmata. These draft genomes provide new data for studying species diversity and function within terrestrial geothermal spring archaeal communities, thus contributing to the conservation and utilization of thermophilic and hyperthermophilic microbial resources., Competing Interests: Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Background: Recurrent Non-Tuberculous Mycobacterial Pulmonary Disease (NTM-PD) related to treatment with Secukinumab has not been previously documented., Case Presentation: Despite adherence to treatment and avoiding hot springs, a plaque psoriasis patient experienced persistent NTM-PD relapses., Conclusions: There is potential association between Secukinumab, an IL-17A inhibitor, and NTM disease, echoing anti-TNF biologics' NTM risk, indicating the urgent need for further research on pathogenic mechanisms and risk factors., Competing Interests: Declarations. Ethics approval and consent to participate: This case report is approved by the hospital ethics committee. A written and signed consent to publish the information from the patient(s) or their guardian(s) prior to submission was obtained. Consent for publication: Written informed consent was obtained from the patient for the publication of this case report and any accompanying images. The patient has reviewed the manuscript and consented to the inclusion of their clinical details in this report. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

Thermomonas hydrothermalis, a thermophilic bacterium isolated from hot springs, exhibits unique genomic features that underpin its adaptability to extreme environments and its potential in industrial biotechnology. In this study, we present a comparative genomic analysis of two strains, DSM 14834 and HOT.CON.106, revealing distinct metabolic pathways and stress response mechanisms. The genome annotation highlighted strain-specific variations, such as enhanced motility and chemotaxis capabilities in HOT.CON.106 and a stronger genomic stability emphasis in DSM 14834. Comparative analysis with other Thermomonas species demonstrated that T. hydrothermalis possesses a unique genomic architecture, including genes for thermostable enzymes (e.g., amylases and pullulanases) and secondary metabolite biosynthesis. These enzymes and metabolites have significant industrial potential in high-temperature processes such as bioenergy production, bioplastics synthesis, and bioremediation. The findings underscore the relative differentiation between the strains and their broader implications for sustainable biotechnology, offering a basis for further exploration of thermophilic microorganisms in industrial applications., Competing Interests: Declarations. Competing interests: The authors declare no competing interests. Conflict of interest: The authors declare no competing interests. Ethical approval: This article does not include any studies with human or animal participants., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

This study assesses halophilic archaea's phylogenetic diversity in southern Tunisia's geothermal water. In the arid southern regions, limited surface freshwater resources make geothermal waters a vital source for oases and greenhouse irrigation. Three samples, including water, sediment, and halite soil crust, were collected downstream of two geothermal springs of the Ksar Ghilane (KGH) and Zaouet Al Aness (ZAN) oases, Tunisia. The samples were subjected to 16S rRNA gene sequencing using the Illumina Miseq sequencing approach. Several haloarchaea were identified in the geothermal springs. The average taxonomic composition revealed that 20 out of 33 genera were shared between the two geothermal sources, with uneven distribution, where the Halogranum genus was the most represented genus with an abundance of 18.9% and 11.58% for ZAW and KGH, respectively. Several unique site-specific genera were observed: Halonotius, Halopelagius, Natronorubrum, and Haloarcula in ZAN, and Haloprofundus, Halomarina, Halovivax, Haloplanus, Natrinema, Halobium, Natronoarchaeum, and Haloterrigena in the KGH pool. Most genus members are typically found in low-salinity ecosystems. These findings suggest that haloarchaea can disperse downstream from geothermal sources and may survive temperature and chemical fluctuations in the runoff., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

A novel Gram-negative, motile, rod-shaped bacterium, designated 4137-cl T , was isolated from a thermal spring of North Ossetia (Russian Federation). Strain 4137-cl T grew at 30-50 °C (optimum 42 °C) with 0-3.5% NaCl (optimum 0-0.3%) and within pH range 4.0-8.7 (optimum pH 6.8-7.3). It was a strictly anaerobic microorganism capable of fermentation and respiration on organic acids and proteinaceous substrates. Sulfur, sulfite, polysulfide, and arsenate were used as electron acceptors. In addition to heterotrophic growth it grew autotrophically with H 2 /CO 2 . The major fatty acids were C 16:1 ω8c and C 16:0 . The size of the genome and genomic DNA G+C content of strain 4137-cl T were 4.5 Mb and 59.2%, respectively. According to the 16S rRNA gene sequence and conserved protein sequences phylogenies, strain 4137-cl T represented a distinct lineage of the family Acetonemataceae within the class Negativicutes. As inferred from the morphology, physiology, chemotaxonomical and phylogenomic analyses, strain 4137-cl T ought to be recognized as a novel genus for which the name Anaeroselena agilis gen. nov., sp. nov., we propose. The type strain is 4137-cl T (=KCTC 25383 T  = VKM B-3575 T )., Competing Interests: Declarations. Conflicts of interest: The authors declare that there are no conflicts of interest. Ethical Approval: This article does not contain any studies with human participants or animals performed by any of the authors. Informed Consent: All authors contributed to the manuscript and agreed to publish. Repositories: The type strain for new taxa have been deposited in KCTC (Korean Collection for Type Cultures) under a number KCTC 25383T, in VKM (All-Russian Collection of Microorganisms) under a number B-3575T., (© 2025. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Phosphatidylglycerol (1,2-diacyl-sn-glycero-3-phospho-glycerol) (PG) is one of the most abundant lipids in biological membranes. However, the chirality of the carbon atom in glycerol phosphate differs among the three kingdoms: bacteria, archaea, and eukaryotes. It is commonly assumed that archaea, as well as bacteria and eukaryotes, produce only one isomer of PG. Archaeal membranes consist of phospholipids with glycerol-1-phosphate in the S configuration, while the phospholipids of the other two kingdoms contain glycerol-3-phosphate with (R) stereochemistry. Another chiral atom is found in glycerol with non-esterified hydroxy groups. Considering the high temperatures that accompanied the origin of life on Earth, it becomes obvious that it is necessary to clarify the importance of membrane lipids in early evolutionary times. To reconstruct the effect of high temperatures on membrane lipids, it is ideal to use microorganisms originating from a thermophilic environment analogous to the early Earth, such as the thermal groundwater of the famous spa town of Karlovy Vary. Here, we prepared all four isomers of PG, i.e., (R,S, R,R, S,R), and (S,S), by organic synthesis and analyzed the representation of individual molecular species in seven bacteria isolated from the Karlovy Vary thermal springs using chiral chromatography - mass spectrometry. Our results provide evidence that five of these strains produce all four isomers of PG and that this production is highly dependent on the cultivation temperature. Subsequent analysis by chiral chromatography revealed that the ratio of isomers, enantiomers, and diastereoisomers depends on the cultivation temperature of individual strains., 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.)

Thermophilic microbial communities growing in low-oxygen environments often contain early-evolved archaea and bacteria, which hold clues regarding mechanisms of cellular respiration relevant to early life. Here, we conducted replicate metagenomic, metatranscriptomic, microscopic, and geochemical analyses on two hyperthermophilic (82-84 °C) filamentous microbial communities (Conch and Octopus Springs, Yellowstone National Park, WY) to understand the role of oxygen, sulfur, and arsenic in energy conservation and community composition. We report that hyperthermophiles within the Aquificota (Thermocrinis), Pyropristinus (Caldipriscus), and Thermoproteota (Pyrobaculum) are abundant in both communities; however, higher oxygen results in a greater diversity of aerobic heterotrophs. Metatranscriptomics revealed major shifts in respiratory pathways of keystone chemolithotrophs due to differences in oxygen versus sulfide. Specifically, early-evolved hyperthermophiles express high levels of high-affinity cytochrome bd and CydAA' oxidases in suboxic sulfidic environments and low-affinity heme Cu oxidases under microaerobic conditions. These energy-conservation mechanisms using cytochrome oxidases in high-temperature, low-oxygen habitats likely played a crucial role in the early evolution of microbial life., Competing Interests: Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Photosynthetic microbial mats in hot springs can provide insights into the diel behaviors of communities in extreme environments. In this habitat, photosynthesis dominates during the day, leading to super-oxic conditions, with a rapid transition to fermentation and anoxia at night. Multiple samples were collected from two springs over several years to generate metagenomic and metatranscriptomic datasets. Metagenome-assembled genomes comprised 71 taxa (in 19 different phyla), of which 12 core taxa were present at high abundance in both springs. The eight most active taxa identified by metatranscriptomics were an oxygenic cyanobacterium (Synechococcus sp.), five anoxygenic phototrophs from three different phyla, and two understudied heterotrophs from phylum Armatimonadota. In all eight taxa, a significant fraction of genes exhibited a diel expression pattern, although peak timing varied considerably. The two abundant heterotrophs exhibit starkly different peak timing of expression, which we propose is shaped by their metabolic and genomic potential to use carbon sources that become differentially available during the diel cycle. Network analysis revealed pathway expression patterns that had not previously been linked to diel cycles, including ribosome biogenesis and chaperones. This provides a framework for analyzing metabolically coupled communities and the dominant role of the diel cycle., (© The Author(s) 2025. Published by Oxford University Press on behalf of the International Society for Microbial Ecology.)

Sulfidic hot springs harbor unique microbial communities and are important in mercury (Hg) species transformations, although the fine scale drivers of these processes remain poorly understood. Here we studied Hg speciation in water, biofilms, and sediment across three sampling seasons in a French sulfidic hot spring with low Hg concentrations. Microbial Hg species methylation and demethylation potentials were evaluated using incubation experiments with species-specific Hg isotope tracers. Temporal variation in inorganic Hg (iHg) and methylmercury (MeHg) concentrations in water, biofilm, and sediment was observed. The incubation of microbial communities in biofilms and sediment under dark conditions exhibited low iHg methylation potentials, whereas a significant extent of biotic MeHg demethylation to oxidized iHg was found in relation to MeHg concentrations. Results from microbial diversity (16S rDNA) and the metabolic inhibition experiments suggest an important role of sulfur-linked bacterial metabolism dynamics. Specifically, sulfate-reducers and anoxygenic phototrophs were important factors in the regulation of MeHg concentrations in our study site. Overall, the observed dominance of microbial MeHg demethylation demonstrates a strong Hg detoxification capacity in sulfidic aquatic environments., 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.)

Active geothermal systems are relatively rare in Antarctica and represent metaphorical islands ideal to study microbial dispersal. In this study, we tested the macro-ecological concept that high dispersal rates result in communities being dominated by either habitat generalists or specialists by investigating the microbial communities on four geographically separated geothermal sites on three Antarctic volcanoes (Mts. Erebus, Melbourne, and Rittman). We found that the microbial communities at higher temperature (max 65°C) sites (Tramway Ridge on Erebus and Rittmann) were unique from each other and were dominated by a variety of novel Archaea from class Nitrososphaeria, while lower temperature (max 50°C) sites (Western Crater on Erebus and Melbourne) had characteristically mesophilic communities (Planctomycetes, Acidobacteriota, etc.) that were highly similar. We found that 97% of the detected microbial taxa were regional habitat specialists, with no generalists, with community assembly driven by high dispersal rates and drift (25% and 30% of community assembly, respectively), not environmental selection. Our results indicate that for microbial communities experiencing high dispersal rates between isolated communities, habitat specialists may tend to out-compete habitat generalists., (© 2025 The Author(s). Environmental Microbiology published by John Wiley & Sons Ltd.)

A thermophilic cellulase-producing bacterium, strain HSW-8 T , isolated from hot spring waters in South Korea, was subjected to a taxonomic analysis. Cells of strain HSW-8 T were gram-stain-negative, facultatively anaerobic, rod-shaped, with optimum growth at 45 °C, pH 7.0, in the presence of 0% (w/v) NaCl. Strain HSW-8 T showed the highest 16S rRNA gene sequence similarity to Sinimarinibacterium flocculans NH6-24 T (97.52%), followed by Fontimonas thermophila DSM 23609 T (96.97%), Solimonas flava CW-KD 4 T (95.24%), and Solimonas variicoloris DSM 15731 T (95.18%). Based on 16S rRNA phylogeny, strain HSW-8 T is phylogenetically closely related to Fontimonas thermophila DSM 23609 T and Sinimarinibacterium flocculans DSM 104150 T and could be distinguished from the type species based on their phenotypic properties. The genome length of strain HSW-8 T was 3.32 Mbp with a 67.33% G + C content. The average nucleotide identity and digital DNA-DNA hybridization values between strain HSW-8 T and its closely related type strains were 75.4-83.2 and 20.2-26.2%, respectively. Summed feature 8 (C 18:1 ω7c and/or C 18:1 ω6c), C 16:0, and iso-C 16:0 identified the major fatty acids (> 10%). Phosphatidylglycerol and phosphatidylethanolamine were demonstrated as the major polar lipids while the respiratory quinone is ubiquinone-8. Strain HSW-8 T exhibited multiple adaptations for survival at high temperatures, including diverse potential motility mechanisms and toxin-antitoxin systems, as evidenced by both phenotypic characteristics and genomic analysis. Based on genotypic and phenotypic features, strain HSW-8 T (= KCTC 92765 T  = GDMCC 1.4313 T ) represents a novel Sinimarinibacterium species, in which the name Sinimarinibacterium thermocellulolyticum sp. nov. is proposed., Competing Interests: Declarations. Conflict of interest: The authors declare no competing interests., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The Kuril Islands are located in the Far-East of Russia and enriched with shallow and terrestrial hot springs. Prokaryotic diversity of Kuril geothermal environments has been studied fragmentarily and mainly by culture-dependent methods. We performed the first large-scale investigation of microbial communities, inhabited more than 30 terrestrial hot springs of Kunashir and Iturup Islands, analyzed by 16S rRNA gene fragment amplicon sequencing, together with chemical analysis of thermal waters and sediments. The Circumneutral Bacterial group containing springs with pH 5.7-8.5 and temperature 40-79 °C possessed the highest biodiversity and consisted almost entirely of Bacteria. Cyanobacteriota (the Leptolyngbyaceae and Oculatellaceae families) and phototrophic Chloroflexota dominated in the microbial mats in hot springs with temperatures up to 60 °C. The higher temperature ones were dominated by Aquificota (Sulfurihydrogenibium and Hydrogenobacter species). The Acidic Bacterial group (pH 2.2-3.6, 41-64 °C) inhabited by the genera Acidithiobacillus, Hydrogenobaculum and Thiomonas. Archaea of Acidianus, Metallosphaera, Thermoplasma and Caldisphaera spp. as well as uncultivated lineages ('Ca. Marsarchaeales', 'Ca. Caldiarchaeum', BSLdp215) were abundant in the Acidic Archaeal group (pH 1.5-2.9, 50-94 °C). The microbial composition of the Kuril hot springs strongly correlated with pH and moderately correlated with water chemistry, while degree of correlation between the communities' compositions with temperature and location was low., Competing Interests: Declarations. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Organic matter (OM) plays an important role in the biogeochemical cycles of carbon, nitrogen, and other elements, shaping the structure of the microbiome and vice versa. However, the molecular composition of OM and its impact on the microbial community in terrestrial geothermal environments remain unclear. In this study, we characterized the OM in water and sediment from a typical geothermal field using ultra-high-resolution Fourier transform ion cyclotron resonance mass spectrometry. By combining high-throughput amplicon sequencing and multivariate analyses, we deciphered the association between OM components and microbial community. A surprisingly high chemodiversity of OM was observed in the waters (11,088 compounds) and sediments (7772 compounds) in geothermal springs. Sulfur-containing organic compounds, a characteristic molecular signature of geothermal springs, accounted for 21 % ± 5 % in waters and 33 % ± 4 % in sediments. Multivariate analyses revealed that both labile and recalcitrant fractions of OM (e.g., carbohydrates intensity and tannins chemodiversity) influenced the structure and function of the microbial community. Co-occurrence networks showed that Proteobacteria and Crenarchaeota accounted for most of the connections with OM in waters (33 % and 15 %, respectively) and sediments (15 % and 12 %, respectively), highlighting their key roles in carbon cycling. This study expands our understanding of the molecular compositions of OM in geothermal springs and highlights its potentially important role in global climate change through microbial carbon cycling., 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.)

Anaerobic ammonium oxidization (Anammox) process plays a crucial role in the global nitrogen cycle and sustainable biological nitrogen removal from wastewater. Although Anammox bacteria have been detected across mesophilic and thermophilic conditions, the direct cultivation of Anammox bacteria from thermal environments has remained elusive. This impedes limiting our understanding of their physiology and ecology in high-temperature habitats. Here, we successfully enriched Anammox bacteria from hot spring sediments at 45 °C, achieving an ammonium oxidation rate of 158.0 mg NH 4 + -N l -1 d -1 , with the genus 'Candidatus Brocadia' presenting 22.9 % of the total microbial community after about 500 days of operation. Metagenomic analysis recovered two high-quality genomes of novel Anammox bacteria, which we designed as 'Candidatus Brocadia thermophilus' and 'Candidatus Brocadia thermoanammoxidans'. Both of them encoded and actively expressed key metabolic genes involved in Anammox process and several genes associated with thermotolerance, demonstrating their remarkable ability to perform Anammox reaction in thermophilic environments. Notably, phylotypes related to 'Candidatus Brocadia thermoanammoxidans' have frequently been retrieved from geographically distinct natural habitats. These findings expand our understanding of thermophilic Anammox bacteria and underscore their potential in the nitrogen cycle of thermal natural and engineering ecosystems., 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.)

Arsenic (As) is a toxic element posing health risks globally, with geothermal environment as one of the hotspots. Arsenic biotransformation is mainly mediated by microorganisms which often employ diverse metabolic strategies for survival. However, the microorganisms responsible for As cycling and their survival strategies in geothermal environment in Tibet, the Third Pole, remain unclear. To address this knowledge gap, we investigated As biotransformation in representative geothermal springs using DNA-stable isotope probing (DNA-SIP) combined with metagenomic sequencing. As(V) reduction to the more toxic As(III) was found to be prevalent. Pseudomonas and Thermincola were identified as the dominant As(V)-reducing bacteria (AsRB). Metagenome-assembled genomes (MAGs) affiliated with AsRB contained abundant genes encoding As(V)-respiratory reductase (arrA, 1044.34 transcripts per million (TPM)), nitrate reduction pathway (e.g., narG), and Wood-Ljungdahl pathway (e.g., acsA), indicating their role as dissimilatory As(V)-reducing prokaryotes (DARPs) with diverse metabolic strategies. Here, Thermincola's potential of As(V) reduction via arrA and carbon fixation via Wood-Ljungdahl pathway was observed for the first time, which was found to be widespread in various ecosystems. Our study unravels the key players driving As biogeochemical cycle in Tibetan geothermal springs and provides insights into the genetic mechanisms enabling their survival in extreme environments., 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.)

Among extremophiles, thermophile microorganisms from geothermal sites have been widely studied. Nevertheless, our knowledge is still relatively poor on microbial communities colonizing fumaroles, which are super-ephemeral habitats, characterized by an only intermittent presence of water. Here we characterized by metabarcoding both bacterial and archaeal communities from hot spring waters and biofilms, together with dry and wet fumaroles, of a geothermal basin in central Italy. Taxa composition of the analyzed samples mirrored that of previous studies, with Thermoproteota dominating among Archaea, while high percentages of thermophiles and spore-forming organisms were retrieved for Bacteria. Cyanobacteriota were the dominant group in biofilms. Community structure was different in the two domains, with highly selected communities of Archaea, less diversified than bacterial ones. Linear regression analyses highlighted significant correlations between diversity and environmental parameters in dry, but not in wet fumaroles. Although ASV numbers displayed different trends for the two different prokaryotic domains (positive correlation with pH for Bacteria, negative correlation for both pH and T for Archaea), such results indicate that even an extremely ephemeral presence of water can influence the importance of temperature and pH as drivers for microbial community structure., (© 2024. The Author(s), under exclusive licence to Springer Nature Japan KK.)

Thermal springs harbour microorganisms, often dominated by cyanobacteria, which form biofilms and microbial mats. These phototrophic organisms release organic exudates into their immediate surroundings, attracting heterotrophic bacteria that contribute to the diversity and functioning of these ecosystems. In this study, the microbial mats from a hydrothermal pool in the Ksar Ghilane oasis in the Grand Erg Oriental of the Desert Tunisia were collected to obtain cyanobacterial cultures formed by single cyanobacterial species. High-throughput analysis showed that while the microbial mat hosted diverse cyanobacteria, laboratory cultures selectively enriched cyanobacteria from the Leptolyngbya, Nodosilinea, and Arthronema. Per each of these genera, multiple non-axenic uni-cyanobacterial cultures were established, totalling 41 cultures. Cyanobacteria taxa mediated the assembly of distinct heterotrophic bacterial communities, with members of the Proteobacteria and Actinobacteria phyla dominating. The bacterial communities of uni-cyanobacterial cultures were densely interconnected, with heterotrophic bacteria preferentially co-occurring with each other. Our study highlighted the complex structures of non-axenic uni-cyanobacterial cultures, where taxonomically distinct cyanobacteria consistently associate with specific groups of heterotrophic bacteria. The observed associations were likely driven by common selection pressures in the laboratory, such as cultivation conditions and specific hosts, and may not necessarily reflect the microbial dynamic occurring in the spring microbial mats., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Early characterizations by morphological identification through light microscopy only revealed the presence of a few microbial lineages and the majority of microbial community at the Chae Son hot spring remains uncharacterized. Therefore, this study aims to examine thermophilic microbial communities at the Chae Son hot spring using next-generation sequencing, including investigating hot spring mineralogy. Results suggest that the Chae Son hot spring (49-75 °C, pH = 6.5-7.0) precipitates digitate structures which comprise mainly silica, and that microbial permineralization is primarily through silicification. Alternating layers of mineralized microbial biofilms and silica were observed in digitate sinter cross-sections, contributing to the build-up of microstromatolites. Molecular results revealed that phylogenetically distinct members of photoautotrophic taxa, Chloroflexota and Cyanobacteriota, dominated spring microbial communities (63.19% relative abundance). Potential primary production processes were mainly through photoautotrophy, with minor lithoautotrophic activities (e.g., sulfur cycling and nitrogen cycling). Moreover, overall microbial community and Cyanobacteriota population alpha diversities significantly decreased with increased temperatures. However, no significant correlation was identified between Chloroflexota population diversity and temperatures. This study provides an update on the microbial community using a high-throughput next-generation sequencing technology, including the mineralogy of the Chae Son hot spring, Northern Thailand., Competing Interests: Declarations. Conflict of interest: The authors declare that they have no conflict of interests., (© 2024. The Author(s), under exclusive licence to Springer Nature Japan KK.)

Microbial amylases should essentially remain active at higher temperatures, and in the alkaline pH and a range of surfactants to be suitable as detergent additives. In the present study, a thermophilic amylase producing bacterium, Bacillus licheniformis UDS-5 was isolated from Unai hot water spring in Gujarat, India. It was identified as a potent amylase producer during starch plate-based screening process. Therefore, the physicochemical parameters influencing amylase production were optimized using Plackett-Burman design and Central Composite Design. The amylase was purified through ammonium sulfate precipitation, size exclusion and ion exchange chromatography, achieving the purification fold and yield to be 9.2 and 40.6%, respectively. The enzyme displayed robust stability and activity across a wide range of temperatures and pHs, with an increased half-life and reduced deactivation rate constant. The amylase exhibited optimal catalysis at 70 °C and pH 8. The kinetic studies revealed Km and Vmax values of 0.58 mg/mL and 2528 μmol/mL/min, respectively. Besides, the purified amylase displayed stability in the presence of various metal ions, surfactants, and chelators suggesting its potential for industrial applications, particularly in the detergent industry. Moreover, detergent application studies demonstrated its efficacy in enhancing washing performance. A comparative profile on washing efficiency of the studied amylase and the commercial amylase with various detergents pointed towards its possible future use as a detergent additive., Competing Interests: Declarations Conflict of interest The authors declare no conflict of interest. Research involving human participants and/or animals This article does not contain any studies with human participants and/or animals performed by any of the authors., (© 2024. The Author(s), under exclusive licence to Springer Nature B.V.)

Few aerobic hyperthermophilic microorganisms degrade polysaccharides. Here, we describe the genome-enabled enrichment and optical tweezer-based isolation of an aerobic polysaccharide-degrading hyperthermophile, Fervidibacter sacchari, previously ascribed to candidate phylum Fervidibacteria. F. sacchari uses polysaccharides and monosaccharides for growth at 65-87.5 °C and expresses 191 carbohydrate-active enzymes (CAZymes) according to RNA-Seq and proteomics, including 31 with unusual glycoside hydrolase domains (GH109, GH177, GH179). Fluorescence in-situ hybridization and nanoscale secondary ion mass spectrometry confirmed rapid assimilation of 13 C-starch in spring sediments. Purified GHs were optimally active at 80-100 °C on ten different polysaccharides. Finally, we propose reassigning Fervidibacteria as a class within phylum Armatimonadota, along with 18 other species, and show that a high number and diversity of CAZymes is a hallmark of the phylum, in both aerobic and anaerobic lineages. Our study establishes Fervidibacteria as hyperthermophilic polysaccharide degraders in terrestrial geothermal springs and suggests a broad role for Armatimonadota in polysaccharide catabolism., (© 2024. The Author(s).)

The study investigated production, characterisation, and biological properties of exopolysaccharide (EPS) from a thermophilic bacterium, Bacillus licheniformis using sucrose as a main carbon source at a temperature of 75 °C, resulting in a yield of 2.87 g/L. The surface topology of EPS was determined using FESEM indicating its porous nature. Subsequently, FTIR was employed to examine EPS and identified the presence of carboxyl and hydroxyl groups, which are believed to be associated with water-holding capacity (WHC). Comparing the FTIR spectrum of various exopolysaccharides, it was inferred that the exopolysaccharide derived from Ramkund closely resembles dextran. EDX and ICP-MS analysis revealed the presence of Sulphur and Selenium which might be involved in the anticancer properties of EPS. This is the first report on bacterial EPS from a hot spring (Ram kund) with antioxidant property, WHC, and high solubility. These properties offer beneficial resources for exploration in the pharmaceutical and agriculture industries.

Global population expansion has increased the demand for food supply and agricultural productivity. Abiotic stressors like temperature have significantly restricted agriculture in cropland and jeopardized food security. Cyanobacteria play a crucial role in fostering sustainable agriculture and ensuring global food security. In the present study, we have assessed the effect of temperatures on diazotrophic free living rice-field and hot-spring cyanobacteria. They were treated to a variable range of temperatures to see the changes in cellular morphology, physiology, and biochemical characteristics. The rise of temperatures induces growth (60 %), total protein (54 %) contents of rice-field cyanobacterium until 25 °C, further treatment results in decline (20 %) at 45 °C. However, growth indices were increased till 35 °C (90 %) in hot-spring cyanobacterium and further treatment did not exhibit a significant decline in the same. However, the reactive oxygen species (ROS) generation and lipid peroxidation (LPO) were higher in rice-field (2.8 and 1.7 fold) as compared to hot-spring cyanobacterium (2.2 and 1.6 fold). In response to temperature, enzymatic antioxidant contents were much higher in hot-spring as compared to rice-field cyanobacterium. Similarly, carotenoid and carbohydrate content was also higher in hot spring (2 fold) as compared to rice-field cyanobacterium (1.5 and 1.2 fold). All these data collectively suggest that hot-spring (Nostoc sp. strain VKB02) has a higher thermoprotective capacity with novel defense mechanisms as compared to rice-field cyanobacterium (Anabaena sp. strain VKB01). These findings contributed to a better understanding of the temperature stress, improvement of agricultural productivity and future welfare of green ecosystems., 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 Masson SAS. All rights reserved.)

Representatives of the genus Thermodesulfovibrio are widespread thermophilic sulfate-reducing bacteria. The genus currently includes five species with validly published names. Two new Thermodesulfovibrio strains, 3907-1M  T and 3462-1 T , were isolated with molecular hydrogen as an electron donor, sulfate as an electron acceptor and acetate as the carbon source from hot springs of Kunashir Island and Kamchatka Peninsula. Similar to other Thermodesulfovibrio species, the new isolates grew by reduction of sulfate, thiosulfate or Fe (III) with a limited range of electron donors, such as hydrogen (in the presence of acetate), formate (in the presence of acetate), pyruvate and lactate. Surprisingly, strain 3907-1M T proved to be capable of autotrophic growth as well. Up to now, the genus Thermodesulfovibrio was represented by heterotrophic species only. Genome analysis revealed the presence of a gene cluster encoding enzymes of form III RubisCO-mediated transaldolase variant of the Calvin cycle in both strains, but genes encoding ribulose-1,5-bisphosphate carboxylase and phosphoribulokinase in the genome of the strain 3462-1 T contained internal stop codons in their sequences. On the basis of phylogenomic analysis, as well as distinct phenotypic and genomic properties, strain 3907-1M T (=DSM 112797 T  =JCM 39445 T  =VKM B-3594 T  =UQM 41601 T ) is proposed to be classified as Thermodesulfovibrio autotrophicus sp. nov., and strain 3462-1 T (=JCM 39444 T  =VKM B-3714 T  =UQM 41602 T ) - as Thermodesulfovibrio obliviosus sp. nov. Our results demonstrate a chemolithoautotrophic lifestyle in Thermodesulfovibrio representatives, suggesting greater ecological flexibility of this genus than previously assumed., 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.)

Persistent Organic Pollutants (POPs) have been in focus of research due to their massive contamination of environment and bio-accumulation. Bioremediation and high-throughput research have gained momentum to curb the harmful effects of POPs. The present research has explored the microbial diversity of Chumathang Hot Spring, Ladakh, India, through Illumina metagenomic HiSeq 4000 sequencing platform and their potential to degrade persistent pollutants, especially xenobiotics. Taxonomic characterization based on raw metagenomic data illuminated the abundance of members of Pseudomonadota and Actinomyceota. The re-construction of the microbial genomes from assembled contigs and scaffolds using de novo assembler metaSPAdes and their further annotation through contig alignment with available reference genomes elucidated the landscape of the hot spring's microbes. The predominantly occupied key genera reported were Pannonibacter and Novosphingobium. Comparative genomic analysis established evolutionary relationships and functional diversities among hot spring microbial communities. The function annotation through MG-RAST has revealed their metabolic versatility of degrading a wide array of xenobiotic compounds, including caprolactam, dioxin, chlorobenzene, benzoate, and. Further, the hydroxylating dioxygenase (Saro&#95;3901) was identified as a pivotal component in the aromatic degradation pathways, showcasing extensive metabolic interconnectivity. Interestingly, protein interaction network analysis identified hub genes like Saro&#95;1233 (protocatechuate 4,5-dioxygenase alpha subunit), while Saro&#95;3057 (amidase) was noted for its critical role in network communication and control. The resilience of thermal ecosystems, evidenced by robust enzymatic activity and degradation capability among organisms with < 95% genetic similarity, underscores their potential for industrial and bioremediation exploration, emphasizing the importance of preserving and studying biodiverse habitats., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Mt. Erebus, Antarctica, is the southernmost active volcano in the world and harbors diverse geothermally unique ecosystems, including "Subglacial" and "Exposed" features, surrounded by a vast desert of ice and snow. Previous studies, while limited in scope, have highlighted the unique and potentially endemic biota of Mt. Erebus. Here, we provide an amplicon-based biodiversity study across all domains of life and all types of geothermal features, with physicochemical and biological data from 48 samples (39 Exposed and 9 Subglacial) collected through various field seasons. We found potentially high taxonomic novelty among prokaryotes and fungi, supporting past hypotheses of high endemism due to the distinctive and isolated environment; in particular, the large number of taxonomically divergent fungal sequences was surprising. We found that different site types had unique physicochemistry and biota; Exposed sites were warmer than Subglacial (median: 40°C versus 10°C for Exposed and Subglacial, respectively) and tended to have more photosynthetic organisms (Cyanobacteria and Chlorophyta). Subglacial sites had more Actinobacteriota, correlated with greater concentrations of Ca and Mg present. Our results also suggest potential human impacts on these remote, highly significant sites, finding evidence for fungal taxa normally associated with wood decay. In this study, we provide a blueprint for future work aimed at better understanding the novel biota of Mt. Erebus., (© The Author(s) 2024. Published by Oxford University Press on behalf of FEMS.)

Trans-Himalayan hot spring waters rich in boron, chlorine, sodium and sulfur (but poor in calcium and silicon) are known based on PCR-amplified 16S rRNA gene sequence data to harbor high diversities of infiltrating bacterial mesophiles. Yet, little is known about the community structure and functions, primary productivity, mutual interactions, and thermal adaptations of the microorganisms present in the steaming waters discharged by these geochemically peculiar spring systems. We revealed these aspects of a bacteria-dominated microbiome (microbial cell density ~8.5 × 104 mL-1; live:dead cell ratio 1.7) thriving in the boiling (85°C) fluid vented by a sulfur-borax spring called Lotus Pond, situated at 4436 m above the mean sea-level, in the Puga valley of eastern Ladakh, on the Changthang plateau. Assembly, annotation, and population-binning of >15-GB metagenomic sequence illuminated the numeral predominance of Aquificae. While members of this phylum accounted for 80% of all 16S rRNA-encoding reads within the metagenomic dataset, 14% of such reads were attributed to Proteobacteria. Post assembly, only 25% of all protein-coding genes identified were attributable to Aquificae, whereas 41% was ascribed to Proteobacteria. Annotation of metagenomic reads encoding 16S rRNAs, and/or PCR-amplified 16S rRNA genes, identified 163 bacterial genera, out of which 66 had been detected in past investigations of Lotus Pond's vent-water via 16S amplicon sequencing. Among these 66, Fervidobacterium, Halomonas, Hydrogenobacter, Paracoccus, Sulfurihydrogenibium, Tepidimonas, Thermus and Thiofaba (or their close phylogenomic relatives) were presently detected as metagenome-assembled genomes (MAGs). Remarkably, the Hydrogenobacter related MAG alone accounted for ~56% of the entire metagenome, even though only 15 out of the 66 genera consistently present in Lotus Pond's vent-water have strains growing in the laboratory at >45°C, reflecting the continued existence of the mesophiles in the ecosystem. Furthermore, the metagenome was replete with genes crucial for thermal adaptation in the context of Lotus Pond's geochemistry and topography. In terms of sequence similarity, a majority of those genes were attributable to phylogenetic relatives of mesophilic bacteria, while functionally they rendered functions such as encoding heat shock proteins, molecular chaperones, and chaperonin complexes; proteins controlling/modulating/inhibiting DNA gyrase; universal stress proteins; methionine sulfoxide reductases; fatty acid desaturases; different toxin-antitoxin systems; enzymes protecting against oxidative damage; proteins conferring flagellar structure/function, chemotaxis, cell adhesion/aggregation, biofilm formation, and quorum sensing. The Lotus Pond Aquificae not only dominated the microbiome numerically but also acted potentially as the main primary producers of the ecosystem, with chemolithotrophic sulfur oxidation (Sox) being the fundamental bioenergetic mechanism, and reductive tricarboxylic acid (rTCA) cycle the predominant carbon fixation pathway. The Lotus Pond metagenome contained several genes directly or indirectly related to virulence functions, biosynthesis of secondary metabolites including antibiotics, antibiotic resistance, and multi-drug efflux pumping. A large proportion of these genes being attributable to Aquificae, and Proteobacteria (very few were ascribed to Archaea), it could be worth exploring in the future whether antibiosis helped the Aquificae overcome niche overlap with other thermophiles (especially those belonging to Archaea), besides exacerbating the bioenergetic costs of thermal endurance for the mesophilic intruders of the ecosystem., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Mondal 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.)

Exopolysaccharides (EPSs), a constitutive part of bacterial biofilm, act as a protecting sheath to the extremophilic bacteria and are of high industrial value. In this study, we elucidate a new EPS produced by thermotolerant (growth from 34-44 °C) strain Pseudomonas alcaligenes Med1 from Medano hot spring (39.1 °C surface temperature, pH 7.1) located in the Central Andean Mountains of Chile. Bacterial growth was screened for temperature tolerance (10-60 °C) to confirm the thermotolerance behaviour. Physicochemical properties of the EPS were characterized by different techniques: Scanning Electron Microscopy- Energy Dispersive X-ray Spectroscopy (SEM-EDS), Atomic Force Microscopy (AFM), High-Performance Liquid Chromatography (HPLC), Gel permeation chromatography (GPC), Fourier Transform Infrared Spectroscopy (FTIR), Nuclear Magnetic Resonance (NMR), and Thermogravimetric analysis (TGA). Whole genome of P. alcaligenes Med1 has also been studied in detail to correlate the structural and functional characteristics with genomic insight. The EPS demonstrated amorphous surface roughness composed of evenly distributed macromolecular lumps composed of mainly carbon and oxygen. The monosaccharide analysis has shown the presence of glucose, galactose, and mannose sugars at different ratios. TGA revealed the high thermal stability (315.3 °C) of the polysaccharide. The GPC has shown that Med1 is a low molecular weight polysaccharide (34.8 kDa) with low PI. The 2D-NMR linkage analysis suggests a diverse array of glycosidic bonds within the exopolysaccharide structure. The functional properties of the EPS were evaluated for food industry applications, specifically for antioxidant (DPPH, FRAP an H 2 O 2 ). Extracted Med1 EPS revealed significant emulsification activity against different food grade vegetative oils (Coconut oil, Corn oil, Canola oil, Avocado oil, Sunflower oil, Olive oil, and Sesame oil). The highest 33.9% flocculation activity was observed with 60 mg L -1 EPS concentration. It showed water-holding (WHC) of 107.6% and oil-holding (OHC) capacity of 110.8%. The functional EPS produced by Pseudomonas alcaligenes Med1 from Central Andean Chilean hot spring of central Chile can be a useful additive for the food-processing industry., (© 2024. The Author(s).)

Objectives: Indonesia's location at the convergence of multiple tectonic plates results in a unique geomorphological feature with abundant hot springs. This study pioneers the metagenomic exploration of Indonesian hot springs, harbouring unique life forms despite high temperatures. The microbial community of hot springs is taxonomically versatile and biotechnologically valuable. 16s rRNA amplicon sequencing of the metagenome is a viable option for the microbiome investigation. This study utilized Oxford Nanopore's long-read 16 S rRNA sequencing for enhanced species identification, improved detection of rare members, and a more detailed community composition profile., Data Description: Water samples were taken from three hot springs of the Bali, Indonesia (i) Angseri, 8.362503 S, 115.133452 E; (ii) Banjar, 8.210270 S, 114.967063 E; and (iii) Batur, 8.228806 S, 115.404829 E. BioLit Genomic DNA Extraction Kit (SRL, Mumbai, India) was used to isolate DNA from water samples. The quantity and quality of the DNA were determined using a NanoDrop™ spectrophotometer and a Qubit fluorometer (Thermo Fisher Scientific, USA). The library was created using Oxford Nanopore Technology kits, and the sequencing was done using Oxford Nanopore's GridION platform. All sequencing data was obtained in FASTQ files and filtered using NanoFilt software. This dataset is valuable for searching novel bacteria diversity and their existence., (© 2024. The Author(s).)

Few described archaeal, and fewer bacterial, lineages thrive under salt-saturating conditions, such as solar saltern crystallizers (salinity above 30% w/v). They accumulate molar K + cytoplasmic concentrations to maintain osmotic balance ('salt-in' strategy) and have proteins adaptively enriched in negatively charged acidic amino acids. Here we analysed metagenomes and metagenome-assembled genomes from geothermally influenced hypersaline ecosystems with increasing chaotropicity in the Danakil Depression. Normalized abundances of universal single-copy genes confirmed that haloarchaea and Nanohaloarchaeota encompass 99% of microbial communities in the near-life-limiting conditions of the Western-Canyon Lakes. Danakil metagenome- and metagenome-assembled-genome-inferred proteomes, compared with those of freshwater, seawater and solar saltern ponds up to saturation (6-14-32% salinity), showed that Western-Canyon Lake archaea encode the most acidic proteomes ever observed (median protein isoelectric points ≤4.4). We identified previously undescribed haloarchaeal families as well as an Aenigmatarchaeota family and a bacterial phylum independently adapted to extreme halophily. Despite phylum-level diversity decreasing with increasing salinity-chaotropicity, and unlike in solar salterns, adapted archaea exceedingly diversified in Danakil ecosystems, challenging the notion of decreasing diversity under extreme conditions. Metabolic flexibility to utilize multiple energy and carbon resources generated by local hydrothermalism along feast-and-famine strategies seemingly shapes microbial diversity in these ecosystems near life limits., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Metagenomic analysis was conducted to assess the microbial community in the high-altitude Tamdykul geothermal spring in Tajikistan. This analysis yielded six high-quality bins from the members of Thermaceae, Aquificaceae, and Halothiobacillaceae, with a 41.2%, 19.7%, and 18.1% share in the total metagenome, respectively. Minor components included Schleiferia thermophila (1.6%) and members of the archaeal taxa Pyrobaculum (1.2%) and Desulfurococcaceae (0.7%). Further analysis of the metagenome-assembled genome (MAG) from the Desulfurococcaceae family (MAG002) revealed novel taxonomy with only 80.95% closest placement average nucleotide identity value to its most closely related member of the Desulfurococcaceae family, which is part of the Thermoproteota phylum comprising hyperthermophilic members widespread in geothermal environments. MAG002 consisted of 1.3 Mbp, distributed into 48 contigs with 1504 predicted coding sequences, had an average GC content of 41.3%, a completeness and contamination rate of 98.7% and 2.6%, respectively, and branched phylogenetically between the Ignisphaera and Zestosphaera lineages. Digital DNA-DNA hybridization values compared with Ignisphaera aggregans and Zestosphaera tikiterensis were 33.7% and 19.4%, respectively, suggesting that this MAG represented a novel species and genus. Its 16S rRNA gene contained a large 421 bp intron. It encodes a complete gluconeogenesis pathway involving a bifunctional fructose-1,6-bisphosphate phosphatase/aldolase; however, the glycolysis pathway is incomplete. The ribulose monophosphate pathway enzymes could be used for pentose synthesis. MAG002 encodes several hydrogen-evolving hydrogenases, with possible roles as hydrogen sinks during fermentation. We propose the name Zestomicrobium tamdykulense gen. nov. sp. nov. for this organism; it is the first thermophilic genome reported from Tajikistan., (© 2024 The Author(s). MicrobiologyOpen published by John Wiley & Sons Ltd.)

Thermophilic cyanobacteria thrive in extreme environments, making their thermoresistant enzymes valuable for industrial applications. Common habitats include hot springs, which act as evolutionary accelerators for speciation due to geographical isolation. The family Thermosynechococcaceae comprises thermophilic cyanobacteria known for their ability to thrive in high-temperature environments. These bacteria are notable for their photosynthetic capabilities, significantly contributing to primary production in extreme habitats. Members of Thermosynechococcaceae exhibit unique adaptations that allow them to perform photosynthesis efficiently at elevated temperatures, making them subjects of interest for studies on microbial ecology, evolution, and potential biotechnological applications. In this study, the genome of a thermophilic cyanobacterium, isolated from a hot spring near Okahandja in Namibia, was sequenced using a PacBio Sequel IIe long-read platform. Cultivations were performed at elevated temperatures of 40, 50, and 55°C, followed by proteome analyses based on the annotated genome. Phylogenetic investigations, informed by the 16S rRNA gene and aligned nucleotide identity (ANI), suggest that the novel cyanobacterium is a member of the family Thermosynechococcaceae. Furthermore, the new species was assigned to a separate branch, potentially representing a novel genus. Whole-genome alignments supported this finding, revealing few conserved regions and multiple genetic rearrangement events. Additionally, 129 proteins were identified as differentially expressed in a temperature-dependent manner. The results of this study broaden our understanding of cyanobacterial adaptation to extreme environments, providing a novel high-quality genome of Thermosynechococcaceae cyanobacterium sp. Okahandja and several promising candidate proteins for expression and characterization studies., (© 2024 The Author(s). MicrobiologyOpen published by John Wiley & Sons Ltd.)

Geothermal features in Antarctica provide favorable conditions for diverse microorganisms, yet their genomic diversity remains poorly understood. Here, we present an integrated dataset comprising PacBio HiFi and Hi-C metagenomic sequencing, along with single-cell amplified genomes (SAGs) from two high-altitude geothermal sites, Mount Melbourne and Mount Rittmann, in Antarctica. The long-read HiFi sequencing, coupled with Hi-C, enhances the understanding of microbiome diversity and functionality in this unique ecosystem by providing more complete and accurate genomic information. SAGs complement this by recovering rare microbial taxa and offering a strain-resolved perspective. This dataset aims to deepen our understanding of microbial evolution and ecology in Antarctic geothermal environments, and facilitate cross-comparison with other geothermal environments globally., (© 2024. The Author(s).)

Microbial communities exhibit intricate interactions underpinned by metabolic dependencies. To elucidate these dependencies, we present a workflow utilizing random matrix theory on metagenome-assembled genomes to construct co-occurrence and metabolic complementarity networks. We apply this approach to a temperature gradient hot spring, unraveling the interplay between thermal stress and metabolic cooperation. Our analysis reveals an increase in the frequency of metabolic interactions with rising temperatures. Amino acids, coenzyme A derivatives, and carbohydrates emerge as key exchange metabolites, forming the foundation for syntrophic dependencies, in which commensalistic interactions take a greater proportion than mutualistic ones. These metabolic exchanges are most prevalent between phylogenetically distant species, especially archaea-bacteria collaborations, as a crucial adaptation to harsh environments. Furthermore, we identify a significant positive correlation between basal metabolite exchange and genome size disparity, potentially signifying a means for streamlined genomes to leverage cooperation with metabolically richer partners. This phenomenon is also confirmed by another composting system which has a similar wide range of temperature fluctuations. Our workflow provides a feasible way to decipher the metabolic complementarity mechanisms underlying microbial interactions, and our findings suggested environmental stress regulates the cooperative strategies of thermophiles, while these dependencies have been potentially hardwired into their genomes during co-evolutions., (© 2024. The Author(s).)

Biodegradation stands as an eco-friendly and effective approach for organic contaminant remediation. However, research on microorganisms degrading sodium benzoate contaminants in extreme environments remains limited. In this study, we report to display the isolation of a novel hot spring enriched cultures with sodium benzoate (400 mg/L) as the sole carbon source. The results revealed that the phylum Pseudomonadota was the potential sodium benzoate degrader and a novel genus within the family Geminicoccaceae of this phylum. The isolated strain was named Benzoatithermus flavus SYSU G07066 T and was isolated from HNT-2 hot spring samples. Genomic analysis revealed that SYSU G07066 T carried benABC genes and physiological experiments indicated the ability to utilize sodium benzoate as a sole carbon source for growth, which was further confirmed by transcriptomic data with expression of benABC. Phylogenetic analysis suggested that Horizontal Gene Transfer (HGT) plays a significant role in acquiring sodium benzoate degradation capability among prokaryotes, and SYSU G07066 T might have acquired benABC genes through HGT from the family Acetobacteraceae. The discovery of the first microorganism with sodium benzoate degradation function from a hot spring enhances our understanding of the diverse functions within the family Geminicoccaceae. This study unearths the first novel genus capable of efficiently degrading sodium benzoate and its evolution history at high temperatures, holding promising industrial applications, and provides a new perspective for further exploring the application potential of hot spring "microbial dark matter"., 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.)

Highly diverse phages infecting thermophilic bacteria of the Thermus genus have been isolated over the years from hot springs around the world. Many of these phages are unique, rely on highly unusual developmental strategies, and encode novel enzymes. The variety of Thermus phages is clearly undersampled, as evidenced, for example, by a paucity of phage-matching spacers in Thermus CRISPR arrays. Using water samples collected from hot springs in the Kunashir Island from the Kuril archipelago and from the Tsaishi and Nokalakevi districts in the Republic of Georgia, we isolated several distinct phages infecting laboratory strains of Thermus thermophilus . Genomic sequence analysis of 11 phages revealed both close relatives of previously described Thermus phages isolated from geographically distant sites, as well as phages with very limited similarity to earlier isolates. Comparative analysis allowed us to predict several accessory phage genes whose products may be involved in host defense/interviral warfare, including a putative Type V CRISPR- cas system.

Elemental sulfur (S 8 0 )-oxidising Sulfolobales (Archaea) dominate high-temperature acidic hot springs (>80°C, pH <4). However, genomic analyses of S 8 0 -oxidising members of the Sulfolobales reveal a patchy distribution of genes encoding sulfur oxygenase reductase (SOR), an S 8 0 disproportionating enzyme attributed to S 8 0 oxidation. Here, we report the S 8 0 -dependent growth of two Sulfolobales strains previously isolated from acidic hot springs in Yellowstone National Park, one of which associated with bulk S 8 0 during growth and one that did not. The genomes of each strain encoded different sulfur metabolism enzymes, with only one encoding SOR. Dialysis membrane experiments showed that direct contact is not required for S 8 0 oxidation in the SOR-encoding strain. This is attributed to the generation of hydrogen sulfide (H 2 S) from S 8 0 disproportionation that can diffuse out of the cell to solubilise bulk S 8 0 to form soluble polysulfides (S x 2- ) and/or S 8 0 nanoparticles that readily diffuse across dialysis membranes. The Sulfolobales strain lacking SOR required direct contact to oxidise S 8 0 , which could be overcome by the addition of H 2 S. High concentrations of S 8 0 inhibited the growth of both strains. These results implicate alternative strategies to acquire and metabolise sulfur in Sulfolobales and have implications for their distribution and ecology in their hot spring habitats., (© 2024 The Author(s). Environmental Microbiology published by John Wiley & Sons Ltd.)

A novel strictly anaerobic hyperthermophilic archaeon, strain 4213-co T , was isolated from a terrestrial hot spring in the Uzon Caldera, Kamchatka (Russian Federation). Coccoid cells were present singly, in pairs, or aggregates, and occasionally were motile. The strain grew at 75-100 °C and within a pH range of 5.4-8.2 with the optimum at 92 °C and pH 6.4-6.7. Strain 4213-co T was a chemoorganoheterotroph, growing on proteinaceous substrates and mono-, di- and polysaccharides (starch, guar gum, xanthan gum). It did not require sodium chloride for growth. The complete genome of strain 4213-co T was 1.74 Mbp in size; its G+C content was 36.18 %. Genome analysis allowed to identify 25 genes encoding glycosidases involved in polysaccharide hydrolysis as well as genes of ADP-forming acetate-CoA ligase, lactate dehydrogenase and two [NiFe] hydrogenases responsible for acetate, lactate and hydrogen formation during fermentation. Moreover gene cluster encoding archaellum subunits was found. According to the phylogenomic analysis strain 4213-co T formed a species-level phylogenetic lineage within Ignisphaera genus. Our phylogenomic analysis also supports the delineation of the Ignisphaera genus into a separate family Ignisphaeraceae, as recently published. Here we propose a novel species Ignisphaera cupida, sp. nov. with type strain 4213-co T (=JCM 39446 T =VKM B-3715 T =UQM 41593 T ). Ecogenomic analysis showed that representatives of the Ignisphaera are thermophilic archaea, the majority of them were found in terrestrial hot springs and deep-sea hydrothermal vents. This study allowed a better understanding of physiology and ecology of Ignisphaeraceae - a rather understudied archaeal group., 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.)

A novel facultatively anaerobic moderately thermophilic bacteria, strains 4137-Me T and 4148-Me T , were isolated from hot springs of Karmadon and Ursdon, respectively (North Ossetia, Russian Federation). Gram-negative, motile rods were present singly, in pairs, rosettes, and aggregates, or formed biofilms. Both strains grew optimally at 50-55 °C, pH 7.0 and did not require sodium chloride or yeast extract for growth. They were chemoorganoheterotrophs, growing on mono-, di- and polysaccharides (cellulose, starch, xylan, lichenan, galactan, xyloglucan, mannan, xanthan gum, guar gum) as well as proteinaceous substrates (gelatin, peptone, beef and yeast extract). Growth under anaerobic conditions was observed in presence and absence of external electron acceptors. Sulfur, thiosulfate, arsenate, Fe-citrate, and ferrihydrite were reduced with acetate, starch, or yeast extract as electron donors. The respiratory quinone was MK-7. Major cellular fatty acids of both strains were iso-C 15:0 , anteiso-C 17:0 , C 15:0 , iso-C 16:0 and additionally iso-C 17:0 for strain 4137-Me T . The size of the genome and genomic DNA G + C content of strain 4137-Me T were 3.24 Mb. and 29.9 %, respectively; for strain 4148-Me T - 3.33 Mb and 30.7 %. According to the 16S rRNA gene sequence and conserved protein sequences phylogenies, strains 4137-Me T and 4148-Me T represented a distinct lineage of the family Melioribacteraceae within the class Ignavibacteria. Based on phylogenetic analysis and phenotypic features, the novel isolates were assigned to a novel genus, for which the name Rosettibacter gen. nov. is proposed. Strain 4148-Me T represents its type species Rosettibacter primus sp. nov., while strain 4137-Me T represents a new species Rosettibacter firmus sp. nov., 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.)

This study explored the metagenome of the Pir Panjal Hot Spring (PPHS) to identify thermostable hydrolases. The carboxypeptidase (CarP) gene was successfully amplified and cloned into Escherichia coli DH5-α cells, followed by expression in E. coli BL21-DE3 cells. The CarP enzyme was comprehensively characterized in vitro. Sequencing analysis revealed an open reading frame encoding a functional protein of 504 amino acids, with a molecular weight of 58.65 kDa and an isoelectric point of 4.81. The CarP protein was purified using Ni-His affinity chromatography, and the experimental molecular weight matched in silico predictions. The enzyme exhibited significant thermostability and alkaliphilic properties, with optimal activity at 70 °C and pH 10.0. Additionally, the presence of Zn +2 ions at concentrations of 5 and 10 mmol/L enhanced protease activity by 1.4 and 1.5-fold, respectively. This study reports the discovery of a novel, multifunctional, and thermostable CarP from hot-spring metagenomes. The enzyme's stability against high temperatures, metal ions, surfactants, and inhibitors, along with its specific substrate interactions, highlights its potential for various biotechnological applications., 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.)

Geyserite is a type of terrestrial siliceous hot spring deposit (sinter) formed subaerially in proximal vent areas, with near-neutral pH, alkali chloride discharge fluids characterized by initial high temperatures (~73°C to up to 100°C) that fluctuate rapidly in relation to dynamic hydrology, seasonality, wind, and other environmental parameters. We analyzed sinters at the Claudia paleogeothermal field from the Late Jurassic (~150 Ma) Deseado Massif geological province, Argentinean Patagonia. The geyserite samples-with spicular to columnar to nodular morphologies-contain abundant microfossils in monotypic assemblages that occur in three diagenetic states of preservation. The best-preserved microfossils consist of vesicle-like structures with radial heteropolar symmetry (~35 μm average diameter), circular apertures, smooth walls lacking ornamentation, and disk- or beret-like shapes. Comparisons with extant, morphologically similar organisms suggest an affinity with the testate amoebae of the Arcella hemisphaerica-Arcella rotundata complex and Centropyxis aculeata strain discoides. These species occur in active geothermal pools between 22°C and 45°C, inconsistent with the temperature of formation of modern geyserites. We propose that the testate amoebae may have colonized the geyserite during cooler phases in between spring-vent eruptive cycles to prey on biofilms. Silica precipitation through intermittent bathing and splashing of fluctuating thermal fluid discharge could have led to their entrapment and fossilization. Petrographic analysis supports cyclicity in paleovent water eruptions and later diagenesis that transformed the opal into quartz. Spatially patchy degradation and modification of the silicified microorganisms resulted in variable preservation quality of the microfossils. This contribution illustrates the importance of microscale analysis to locate early silicification and identify high-quality preservation of fossil remains in siliceous hot spring deposits, which are important in early life studies on Earth and potentially Mars., (© 2024 The Author(s). Geobiology published by John Wiley & Sons Ltd.)

Whole microorganisms are rarely preserved in the fossil record but actively silicifying environments like hot springs provide an opportunity for microbial preservation, making silicifying environments critical for the study of microbial life through time on Earth and possibly other planetary bodies. Yet, the changes that biosignatures may undergo through lithification and burial remain unconstrained. At Steep Cone Geyser in Yellowstone National Park, we collected microbial material from (1) the living system across the active outflows, (2) the silicified areas adjacent to flows, and (3) lithified and buried material to assess the preservation of biosignatures and their changes across the lithification transect. Five biofabrics, built predominantly by Cyanobacteria Geitlerinema, Pseudanabaenaceae, and Leptolyngbya with some filamentous anoxygenic phototrophs contributions, were identified and tracked from the living system through the process of silicification/lithification. In the living systems, δ 30 Si values decrease from +0.13‰ in surficial waters to -2‰ in biomat samples, indicating a kinetic isotope effect potentially induced by increased association with actively growing biofabrics. The fatty acids C 16:1 and iso-C 14:0 and the hydrocarbon C 17:0 were disentangled from confounding signals and determined to be reliable lipid biosignatures for living biofabric builders and tenant microorganisms. Builder and tenant microbial biosignatures were linked to specific Cyanobacteria, anoxygenic phototrophs, and heterotrophs, which are prominent members of the living communities. Upon lithification and burial, silicon isotopes of silicified biomass began to re-equilibrate, increasing from δ 30 Si -2‰ in living biomats to -0.55‰ in lithified samples. Active endolithic microbial communities were identified in lithified samples and were dominated by Cyanobacteria, heterotrophic bacteria, and fungi. Results indicate that distinct microbial communities build and inhabit silicified biofabrics through time and that microbial biosignatures shift over the course of lithification. These findings improve our understanding of how microbial communities silicify, the biomarkers they retain, and transitionary impacts that may occur through lithification and burial., (© 2024 John Wiley & Sons Ltd.)

Puga geothermal geyser and surrounding area, located in the Himalayan Geothermal Belt of the Trans-Himalayan Plateau in Ladakh, India, are very geographically isolated and considered pristine and free of anthropogenic activities. In this study, we have conducted the first metagenomic investigation of the microbes in and around the geyser. The whole genome sequencing analysis showed the presence of a total of 44.8%, 39.7% and 41.4% bacterial phyla in the PugW, PugS, and PugSo samples respectively, 8.6% of archaeal phyla (in all the samples), unclassified (derived from other sequences, PugW: 27.6%, PugS: 27.6%, and PugSo: 15.5%) and unclassified (derived from bacteria, PugW: 12%, PugS: 13.8%, and PugSo: 13.8%). The majority of archaeal sequences were linked to Euryarchaeota (2.84%) while the majority of the bacterial communities that predominated in most geothermal locations were linked to Pseudomonadota (67.14%) and Bacteroidota (12.52%). The abundant bacterial strains at the species level included Dechloromonas aromatica, Acinetobacter baumannii, and Arcobacter butzleri, in all the samples while the most abundant archaeal species were Methanosaeta thermophile, Methanoregula boonei, and Methanosarcina berkeri. Further, this geothermal geyser metagenome has a large number of unique sequences linked to unidentified and unclassified lineages, suggesting a potential source for novel species of microbes and their products. The present study which only examined one of the many geothermal geysers and springs in the Puga geothermal area, should be regarded as a preliminary investigation of the microbiota that live in the geothermal springs on these remote areas. These findings suggest that further investigations should be undertaken to characterize the ecosystems of the Puga geothermal area, which serve as a repository for unidentified microbial lineages., (© 2024. The Author(s) under exclusive licence to Sociedade Brasileira de Microbiologia.)

We acquired and analyzed metagenome and 16S/18S rRNA gene amplicon data of green-colored microbial mats from two hot springs within the Onikobe geothermal region (Miyagi Prefecture, Japan). The two collection sites-Tamago and Warabi-were in proximity and had the same temperature (40 °C), but the Tamago site was connected to a nearby stream, whereas the Warabi site was isolated. Both the amplicon and metagenome data suggest the bacterial, especially cyanobacterial, dominance of the mats; other abundant groups include Chloroflexota, Pseudomonadota, Bacteroidota/Chlorobiota, and Deinococcota. At finer resolution, however, the taxonomic composition entirely differed between the mats. A total of 5 and 21 abundant bacterial 16S rRNA gene OTUs were identified for Tamago and Warabi, respectively; of these, 12 are putative chlorophyll- or rhodopsin-based phototrophs. The presence of phylogenetically diverse microbial eukaryotes was noted, with ciliates and amoebozoans being the most abundant eukaryote groups for Tamago and Warabi, respectively. Fifteen metagenome-assembled genomes (MAGs) were obtained, represented by 13 bacteria, one ciliate (mitochondrion), and one giant virus. A total of 15 novel taxa, including a new deeply branching Chlorobiota species, is noted from the amplicon and MAG data, highlighting the importance of environmental sequencing in uncovering hidden microorganisms., (© 2024. The Author(s), under exclusive licence to Springer Nature Japan KK.)

The geosphere and the microbial biosphere have co-evolved for ~3.8 Ga, with many lines of evidence suggesting a hydrothermal habitat for life's origin. However, the extent that contemporary thermophiles and their hydrothermal habitats reflect those that likely existed on early Earth remains unknown. To address this knowledge gap, 64 geochemical analytes were measured and 1022 metagenome-assembled-genomes (MAGs) were generated from 34 chemosynthetic high-temperature springs in Yellowstone National Park and analysed alongside 444 MAGs from 35 published metagenomes. We used these data to evaluate co-variation in MAG taxonomy, metabolism, and phylogeny as a function of hot spring geochemistry. We found that cohorts of MAGs and their functions are discretely distributed across pH gradients that reflect different geochemical provinces. Acidic or circumneutral/alkaline springs harbor MAGs that branched later and are enriched in sulfur- and arsenic-based O 2 -dependent metabolic pathways that are inconsistent with early Earth conditions. In contrast, moderately acidic springs sourced by volcanic gas harbor earlier-branching MAGs that are enriched in anaerobic, gas-dependent metabolisms (e.g. H 2 , CO 2 , CH 4 metabolism) that have been hypothesized to support early microbial life. Our results provide insight into the influence of redox state in the eco-evolutionary feedbacks between thermophiles and their habitats and suggest moderately acidic springs as early Earth analogs., (© 2024. The Author(s).)

Methanogenic hydrocarbon degradation can be carried out by archaea that couple alkane oxidation directly to methanogenesis, or by syntrophic associations of bacteria with methanogenic archaea. However, metagenomic analyses of methanogenic environments have revealed other archaea with potential for alkane degradation but apparent inability to form methane, suggesting the existence of other modes of syntrophic hydrocarbon degradation. Here, we provide experimental evidence supporting the existence of a third mode of methanogenic degradation of hydrocarbons, mediated by syntrophic cooperation between archaeal partners. We collected sediment samples from a hot spring sediment in Tengchong, China, and enriched Hadarchaeota under methanogenic conditions at 60 °C, using hexadecane as substrate. We named the enriched archaeon Candidatus Melinoarchaeum fermentans DL9YTT1. We used 13 C-substrate incubations, metagenomic, metatranscriptomic and metabolomic analyses to show that Ca. Melinoarchaeum uses alkyl-coenzyme M reductases (ACRs) to activate hexadecane via alkyl-CoM formation. Ca. Melinoarchaeum likely degrades alkanes to carbon dioxide, hydrogen and acetate, which can be used as substrates by hydrogenotrophic and acetoclastic methanogens such as Methanothermobacter and Methanothrix., (© 2024. The Author(s).)

Hot springs are inhabited by specific microbial communities which are reservoirs of novel taxa. In this work strain 4228-RoL T was isolated from the Solnechny hot spring, Uzon Caldera, Kamchatka. Cells of the strain 4228-RoL T were Gram-negative rods forming multicellular filaments. The strain grew optimally at 60 °C and pH 7.0 and fermented various organic compounds including polysaccharides (microcrystalline cellulose, xylan, chitin, starch, dextrin, dextran, beta-glucan, galactomannan, glucomannan, mannan). Major fatty acids were iso-C 17:0 , C 16:0 , C 18:0 , C 20:0 , iso-C 19:0 , anteiso-C 17:0 and C 22:0 . Genome of the strain was of 3.25 Mbp with GC content of 54.2%. Based on the whole genome comparisons and phylogenomic analysis the new isolate was affiliated to a novel species of Thermanaerothrix genus within Anaerolineae class of phylum Chloroflexota, for which the name T. solaris sp. nov. was proposed with 4228-RoL T (= VKM B-3776  T  = UQM 41594  T  = BIM B-2058  T ) as the type strain. 114 CAZymes including 43 glycoside hydrolases were found to be encoded in the genome of strain 4228-RoL T . Cell-bound and extracellular enzymes of strain 4228-RoL T were active against starch, dextran, mannan, xylan and various kinds of celluloses, with the highest activity against beta-glucan. Altogether, growth experiments, enzymatic activities determination and genomic analysis suggested that T. solaris strain 4228-RoL T could serve as a source of glycosidases suitable for plant biomass hydrolysis., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Growing evidence suggests that the hydrochemical properties of geothermal fumaroles may play a crucial role in shaping the diversity and functions of microbial communities in various environments. In the present study, the impact of geothermal furaneols on the microbial communities and their metabolic functions across the rock-soil-plant continuum was explored considering varying distances from the fumarole source. The results revealed that bacterial phylum Proteobacteria was predominant in all sample types, except in the 10 m rock sample, irrespective of the sampling distance. Archaeal phyla, such as Euryarchaeota and Crenarchaeota, were more prevalent in rock and soil samples, whereas bacterial phyla were more prevalent in plant samples. Thermoacidophilic archaeons, including Picrophilus, Ferroplasma, and Thermogymnomonas were dominant in rocks and soil samples of 1 and 5 m distances; acidophilic mesophiles, including Ferrimicrobium and Granulicella were abundant in the rhizoplane samples, whereas rhizosphere-associated microbes including Pseudomonas, Pedobacter, Rhizobium, and Novosphingobium were found dominant in the rhizosphere samples. The functional analysis highlighted the higher expression of sulfur oxidative pathways in the rock and soil samples; dark iron oxidation and nitrate/nitrogen respiratory functions in the rhizosphere samples. The findings underscore microbial adaptations across the rock-soil-plant continuum, emphasizing the intricate relationship between geothermal fumaroles and microbial communities in adjacent ecosystems. These insights offer a crucial understanding of the evolution of microbial life and highlight their pivotal roles in shaping ecosystem dynamics and functions., (© 2024 Wiley‐VCH GmbH.)