Search

Oscillations in the phosphate (Pi ) uptake rates for three species of green algae were examined in a P-limited cyclostat. For Ankistrodesmus convolutus Corda and Chlorella vulgaris Beyerinck, the Pi uptake rates increased during the daytime and decreased at night. In contrast, Chlamydomonas sp. exhibited the opposite uptake pattern. Cell densities also oscillated under a light:dark cycle, dividing at a species-specific timing rather than continuously. In general, the cell densities exhibited an inverse relationship with the Pi uptake rates. A competition experiment between A. convolutus and C. vulgaris in a P-limited cyclostat resulted in the dominance of C. vulgaris , regardless of the relative initial cell concentrations. Chlorella vulgaris also dominated in a mixed culture with Chlamydomonas sp., irrespective of the initial seeding ratio and dilution rate. However, Chlamydomonas sp. and A. convolutus coexisted in the competition experiment with gradual decrease of Chlamydomonas sp. when equally inoculated. Mathematical expressions of the oscillations in the Pi uptake rate and species-specific cell division gate were used to develop a simulation model based on the Droop equation. The simulation results for each of the species conformed reasonably well to the experimental data. The results of the competition experiments also matched the competition simulation predictions quite well, although the experimental competition was generally more delayed than the simulations. In conclusion, the model simulation that incorporated the effect of diel rhythms in nutrient uptake clearly demonstrated that species diversity could be enhanced by different oscillation patterns in resource uptake, even under the condition of limitation by the same resource. [ABSTRACT FROM AUTHOR]

Oscillations in the phosphate (Pi ) uptake rates for three species of green algae were examined in a P-limited cyclostat. For Ankistrodesmus convolutus Corda and Chlorella vulgaris Beyerinck, the Pi uptake rates increased during the daytime and decreased at night. In contrast, Chlamydomonas sp. exhibited the opposite uptake pattern. Cell densities also oscillated under a light:dark cycle, dividing at a species-specific timing rather than continuously. In general, the cell densities exhibited an inverse relationship with the Pi uptake rates. A competition experiment between A. convolutus and C. vulgaris in a P-limited cyclostat resulted in the dominance of C. vulgaris , regardless of the relative initial cell concentrations. Chlorella vulgaris also dominated in a mixed culture with Chlamydomonas sp., irrespective of the initial seeding ratio and dilution rate. However, Chlamydomonas sp. and A. convolutus coexisted in the competition experiment with gradual decrease of Chlamydomonas sp. when equally inoculated. Mathematical expressions of the oscillations in the Pi uptake rate and species-specific cell division gate were used to develop a simulation model based on the Droop equation. The simulation results for each of the species conformed reasonably well to the experimental data. The results of the competition experiments also matched the competition simulation predictions quite well, although the experimental competition was generally more delayed than the simulations. In conclusion, the model simulation that incorporated the effect of diel rhythms in nutrient uptake clearly demonstrated that species diversity could be enhanced by different oscillation patterns in resource uptake, even under the condition of limitation by the same resource. [ABSTRACT FROM AUTHOR]

To investigate the interactions between bacterial species in relation to the biotic and abiotic environmental fluctuations, free-living (FL), nanoparticle-associated (NP), and microparticle-associated (MP) bacterial community compositions (BCCs) were analyzed. A total of 267 samples were collected from July to December 2016 in the dynamic and shallow southern coastal water of Korea. The variations in BCC mostly depended on planktonic size fraction. Network analysis revealed water depth-dependent co-occurrence patterns of coastal bacterial communities. Higher interspecies connectivity was observed within FL bacteria than NP/MP bacteria, suggesting that FL bacteria with a streamlined genome may need other bacterial metabolites for survival, while the NP/MP copiotrophs may have the self-supporting capacity to produce the vital nutrients. The analysis of topological roles of individual OTUs in the network revealed that several groups of metabolically versatile bacteria (the marine Roseobacters, Flavobacteriales, Desulfobacterales, and SAR406 clade) acted as module hubs in different water depth. In conclusion, interspecies interactions dominated in FL bacteria, compared to NP and MP bacteria; modular structures of bacterial communities and keystone species strongly depended on the water depth-derived environmental factors. Furthermore, the multifunctional, versatile FL bacteria could play pivotal roles in dynamic shallow coastal ecosystems. [ABSTRACT FROM AUTHOR]

The biomass and carotenoid productivities of a freshwater microalga, Ettlia sp. YC001 (Chlorophyta, Chlamydomonadales), were investigated in continuous culture systems irradiated with various LEDs. Green light was effectively used by Ettlia sp. for its biomass growth compared to blue and red LED light. This effective use of green light was assumed to be beneficial for Ettlia sp., especially in competition with other microalgae. Thus, in a competition between Ettlia sp. and Chlorella vulgaris, Ettlia sp. out-competed C. vulgaris without losing any overall biomass productivity when green and white LEDs were used simultaneously. However, since Ettlia sp. also showed relatively low oxygen production under green light, further studies are needed on its photosynthesis and biomass production mechanisms. Notwithstanding, LEDs are potentially useful for identifying strain-specific photosynthetic characteristics of microalgae, thereby increasing their biomass productivity and controlling contamination from other microalgae in open culture systems. [ABSTRACT FROM AUTHOR]

The massive proliferation of Microcystis threatens freshwater ecosystems and degrades water quality globally. Understanding the mechanisms that contribute to Microcystis growth is crucial for managing Microcystis blooms. The lifestyles of bacteria can be classified generally into two groups: particle-attached (PA; > 3 µm) and free-living (FL; 0.2–3.0 µm). However, little is known about the response of PA and FL bacteria to Microcystis blooms. Using 16S rRNA gene high-throughput sequencing, we investigated the stability, assembly process, and co-occurrence patterns of PA and FL bacterial communities during distinct bloom stages. PA bacteria were phylogenetically different from their FL counterparts. Microcystis blooms substantially influenced bacterial communities. The time decay relationship model revealed that Microcystis blooms might increase the stability of both PA and FL bacterial communities. A contrasting community assembly mechanism was observed between the PA and FL bacterial communities. Throughout Microcystis blooms, homogeneous selection was the major assembly process that impacted the PA bacterial community, whereas drift explained much of the turnover of the FL bacterial community. Both PA and FL bacterial communities could be separated into modules related to different phases of Microcystis blooms. Microcystis blooms altered the assembly process of PA and FL bacterial communities. PA bacterial community appeared to be more responsive to Microcystis blooms than FL bacteria. Decomposition of Microcystis blooms may enhance cooperation among bacteria. Our findings highlight the importance of studying bacterial lifestyles to understand their functions in regulating Microcystis blooms. Key points: • Microcystis blooms alter the assembly process of PA and FL bacterial communities • Microcystis blooms increase the stability of both PA and FL bacterial communities • PA bacteria seem to be more responsive to Microcystis blooms than FL bacteria [ABSTRACT FROM AUTHOR]

This study used a single strain Ettlia sp. YC001 and two stages to optimize the production of three materials: lipids, lutein, and β-carotene. In the cultivation stage for lutein production, different temperatures, light qualities, and intensities were applied. The highest biomass was obtained at 35 °C, but the maximum lutein productivity of 6.1 mg/L/d achieved at 25 °C. In the stress stage for lipids and β-carotene production, UV-A and nitrogen starvation were applied. While UV stress increased the chlorophyll- a and β-carotene content. The β-carotene, oleic acid, and lipids significantly increased under nitrogen starvation with a high light intensity of 1200 µmol/m 2 /s, plus the Ettlia sp. changed from green to red. The results showed that Ettlia sp. can be an effective microalga for the co-production of lutein, β-carotene, and biodiesel. [ABSTRACT FROM AUTHOR]

A highly settleable microalga, Ettlia sp., was applied to a freshwater recirculating aquaculture system (RAS) of Danio rerio to improve the treatment of nitrogenous compounds. The growth characteristics of the microalgae, water quality parameters, and bacterial communities were monitored for 73 days. In the treatment RAS, the inoculated Ettlia sp. grew up to 1.26 g/L and dominated (>99%) throughout the experiment, whereas naturally occurring microalgae grew to 0.57 g/L in the control RAS. The nitrate, nitrite, and ammonium concentrations in the treatment RAS were reduced by 50.1%, 73.3%, and 24.2%, respectively, compared to the control RAS. A bacterial community analysis showed that Rhodospirillales , Phycisphaerae , Chlorobiales , and Burkholderiales were the major bacterial groups in the later phase of the treatment RAS. Meanwhile, a network analysis among the Ettlia sp., bacterial groups, and environmental parameters, revealed that the bacterial groups played key roles in both water quality improvement and Ettlia sp. growth. In conclusion, the inoculation and growth of the Ettlia sp. and its associated bacteria in the RAS produced beneficial effects on the water quality by reducing the nitrogenous compounds and providing a favorable environment for certain bacterial groups to further improve water quality. [ABSTRACT FROM AUTHOR]

The optimal culture conditions are critical factors for high microalgal biomass and lipid productivity. To optimize the photoautotrophic culture conditions, combination of the pH (regulated by CO 2 supply), dilution rate, and light intensity was systematically investigated for Ettlia sp. YC001 cultivation in a chemostat during 143 days. The biomass productivity increased with the increase in dilution rate and light intensity, but decreased with increasing pH. The average lipid content was 19.8% and statistically non-variable among the tested conditions. The highest biomass and lipid productivities were 1.48 g L −1 d −1 and 291.4 mg L −1 d −1 with a pH of 6.5, dilution rate of 0.78 d −1 , and light intensity of 1500 μmol photons m −2 s −1 . With a sufficient supply of CO 2 and nutrients, the light intensity was the main determinant of the photosynthetic rate. Therefore, the surface-to-volume ratio of a photobioreactor should enable efficient light distribution to enhance microalgal growth. [ABSTRACT FROM AUTHOR]

Cyanobacterial harmful algal blooms (CyanoHABs) are a global concern and pose various hazards to ecosystems and humans. Periphyton is a mixture of heterotrophic and photoautotrophic microorganisms, which effectively mitigated CyanoHABs. However, how periphyton affects free-living (FL) and particle-attached (PA) bacteria and how FL and PA bacterial communities contribute to the control of CyanoHABs remains unclear. Herein, we first characterized the response of FL and PA bacterial communities to periphyton in an outdoor mesocosm setting (1000 L) using high-throughput 16S rRNA gene sequencing data. Pre-incubation of periphyton before inoculation enhanced control efficiency: (1) Periphyton reduced the planktonic chlorophyll-a concentration by 38.6% on day 11; (2) Microcystis and Dolichospermum cell density decreased by 70.8% and 94.8%, respectively. The dissimilarity in microbial interaction networks between the control and treatment was 92.2%, indicating that periphyton changed the bacterial interactions. In response to periphyton, the PA bacterial community exhibited higher stability than the FL bacterial community. Periphyton treatment likely favored the growth of organic matter-degrading bacteria. In addition, Saprospiraceae, Aeromonas, Rhodobacteraceae, and Brevundimonas, which have potential inhibitory effects on cyanobacteria, were enriched in the mesocosm treatment. In summary, our findings suggest that periphyton may mitigate CyanoHABs by altering bacterial communities. [ABSTRACT FROM AUTHOR]

• First record of a Fictibacillus strain with algicidal activity on M. polykrikoides. • 5A8 M lyses M. polykrikoides by both direct attack and secretion of algicides. • 5A8 M produces two algicidal compounds (l -phenylalanine and anthranilic acid). • 5A8 M causes oxidative stress and damages photosynthetic system in M. polykrikoides. Margalefidinium polykrikoides blooms inflict significant economic losses on the aquaculture industry. Utilizing algicidal bacteria to mitigate harmful algal blooms (HABs) has emerged as an environment-friendly approach. Despite numerous reports on algicidal bacteria, few studies have thoroughly elucidated their mechanisms against M. polykrikoides. In this study, we present the first documentation of the algicidal effect of a Fictibacillus strain on M. polykrikoides. Strain 5A8M exhibited algicidal effects through physical attachment and the secretion of extracellular algicidal metabolites. The algicidal activity of strain 5A8M was dose- and time-dependent. When inoculated at a ratio of 10 % (v/v), strain 5A8M induced lysis in 97.9 % of M. polykrikoides after 24 h of co-culture. The active chlorophyll- a and transcriptional levels of key genes in M. polykrikoides decreased under the algicidal influence of strain 5A8M. Furthermore, exposure to the cell-free filtrate of strain 5A8M for 12 h triggered lipid peroxidation in M. polykrikoides , resulting in elevated malondialdehyde levels. Analysis via 1H nuclear magnetic resonance (NMR), 13C NMR, and electrospray ionization-mass spectra identified l -phenylalanine and anthranilic acid as the extracellular algicidal metabolites produced by strain 5A8M. The algicidal activity of l -phenylalanine and anthranilic acid (10 μg/ml) against M. polykrikoides reached 74.6 and 72.5 %, respectively, within 24 h of exposure. Collectively, our findings underscore the considerable potential of strain 5A8M in controlling M. polykrikoides HABs. [Display omitted] [ABSTRACT FROM AUTHOR]

A microcystin-degrading bacterial strain, Blastomonas fulva T2, was isolated from the culture of a microalgae Microcystis. The strain B. fulva T2 is Gram-stain-negative, non-motile, aerobic, non-spore-forming and phototrophic. The cells of B. fulva T2 are able to grow in ranges of temperature from 15 to 37 °C, with a pH of 6 to 8 and a salinity of 0 to 1% NaCl. Here, we sequenced the complete genome of B. fulva T2, aiming to better understand the evolutionary biology and the function of the genus Blastomonas at the molecular level. The complete genome of B. fulva T2 contained a circular chromosome (3,977,381 bp) with 64.3% GC content and a sizable plasmid (145.829 bp) with 60.7% GC content which comprises about 3.5% of the total genetic content. A total of 3842 coding genes, including 46 tRNAs and 6 rRNAs, were predicted in the genome. The genome contains genes for glycolysis, citric acid cycle, Entner–Doudoroff pathways, photoreaction center and bacteriochlorophylla synthesis. A 7.9 K gene cluster containing mlrA, mlrB, mlrC and mlrD1,2,3,4 of microcystin-degrading enzymes was identified. Notably, eight different efflux pumps categorized into RND, ABC and MFS types have been identified in the genome of strain T2. Our findings should provide new insights of the alternative reaction pathway as well as the enzymes which mediated the degradation of microcystin by bacteria, as well as the evolution, architectures, chemical mechanisms and physiological roles of the new bacterial multidrug efflux system. [ABSTRACT FROM AUTHOR]

The number of cyanobacterial harmful algal blooms (cyanoHABs) has increased, leading to the widespread development of prediction models for cyanoHABs. Although bacteria interact closely with cyanobacteria and directly affect cyanoHABs occurrence, related modeling studies have rarely utilized microbial community data compared to environmental data such as water quality. In this study, we built a machine learning model, the multilayer perceptron (MLP), for the prediction of Microcystis dynamics using both bacterial community and weekly water quality data from the Daechung Reservoir and Nakdong River, South Korea. The modeling performance, indicated by the R 2 value, improved to 0.97 in the model combining bacterial community data with environmental factors, compared to 0.78 in the model using only environmental factors. This underscores the importance of microbial communities in cyanoHABs prediction. Through the post-hoc analysis of the MLP models, we revealed that nitrogen sources played a more critical role than phosphorus sources in Microcystis blooms, whereas the bacterial amplicon sequence variants did not have significant differences in their contribution to each other. Similar to the MLP model results, bacterial data also had higher predictability in multiple linear regression (MLR) than environmental data. In both the MLP and MLR models, Microscillaceae showed the strongest association with Microcystis. This modeling approach provides a better understanding of the interactions between bacteria and cyanoHABs, facilitating the development of more accurate and reliable models for cyanoHABs prediction using ambient bacterial data. • MLP model better predicted Microcystis using bacterial community than water quality. • Combining bacterial data with environmental factors enhances predictive accuracy. • Microcystis blooms are more strongly influenced by nitrogen sources than phosphorus. • Robust associations between bacteria and Microcystis are evident in both MLP and MLR. [ABSTRACT FROM AUTHOR]

A Gram-negative, red-colored, and rod-shaped bacterial strain, DH14T, was isolated from a eutrophic reservoir. The 16S rRNA gene sequence analysis showed that strain DH14T was most closely related to Hymenobacter terrigena (98.3% similarity) and Hymenobacter terrae (98.1%). The average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between strain DH14T and its related type strains were below 82.9% and 27.2%, respectively. Strain DH14T contained iso-C15:0 (32.6%), anteiso-C15:0 (14.0%), and summed feature 3 (C16:1ω6c and/or C16:1ω7c) (25.8%) as major cellular fatty acids. The main polar lipids were phosphatidylethanolamine, two unidentified aminophospholipids, and one unidentified lipid. The respiratory quinone was menaquinone 7 (MK-7). The genomic DNA G + C content was 62.1%. These evidences support the classification of strain DH14T as a novel species in the genus Hymenobacter, for which the name Hymenobacter cyanobacteriorum sp. nov. is proposed. The type strain is DH14T (= KCTC 92040T = LMG 32425T). [ABSTRACT FROM AUTHOR]

A Gram-stain-negative, rod-shaped bacterial strain DH6T was isolated from fresh water of the Daechung Reservoir during the Microcystis bloom period. The strain grew at pH 6.0–8.5, at temperature 17–40 °C, and at 0–1% (w/v) NaCl concentration. Comparison of 16S rRNA gene sequence indicated that strain DH6T exhibits the highest similarity with Panacibacter ginsenosidivorans Gsoil 1550T (96.6%). The average nucleotide identity (ANI), digital DNA–DNA hybridization (dDDH), and average amino acid identity (AAI) values of strain DH6T compared to its related type strains were below 74.2%, 22.3%, and 74.8%, respectively. The predominant fatty acids (> 5.0%) were identified as iso-C17:0 3-OH, iso-C13:0, iso-C15:0, C17:0 2-OH, iso-C11:0, anteiso-C13:0, and iso-C15:1 G. The polar lipid profile contained phosphatidylethanolamine, four unidentified aminolipids, and three unidentified lipids. The respiratory quinone was menaquinone 7 (MK-7). The genomic DNA G + C content was 42.6%. Collectively, strain DH6T should be classified as a novel species within the genus Panacibacter, for which the name Panacibacter microcysteis sp. nov. is proposed. The type strain is DH6T (= KCTC 82471T = LMG 32426T). [ABSTRACT FROM AUTHOR]

Abstract: Cyanobacterial blooms in eutrophied water body are generally composed of various genotypes with or without microcystin-producing genes (mcy gene cluster). Thus there is a need for quantification of potent toxin producing strains. The present study aimed at identifying microcystin variants and its producer strains in Durgakund pond, Varanasi, India, based on quantification of cpcBA-IGS and mcyA (condensation domain) genes using real-time PCR and LC–MS. Increase in microcystin concentrations was correlated with increase in mcyA copy number and the level of pigments (chlorophyll a, phycocyanin and carotenoids). Also, selected environmental factors (water temperature, light irradiance, rainfall, pH, N and P) and the concentration of microcystin variants (MC-LR, -RR and -YR) were also assessed in samples during May 2010 to April 2011 to establish the possible correlation among these parameters. Nutrients favored cyanobacterial bloom but it could not be correlated with the levels of microcystin variants and seemed to be geographically specific. Microcystis sp. dominant in the pond comprised potentially toxigenic cells. The ratio of potentially toxigenic Microcystis sp. to that of total Microcystis sp. ranged from 0% to 14%. Such studies paved the way to identify and quantify the most potent microcystin producer in the tropical aquatic body. [Copyright &y& Elsevier]

Abstract: The optimal flocculating conditions for harvesting high-density cultures of Scenedesmus sp. were investigated using inorganic coagulants and the bioflocculant produced by Paenibacillus polymyxa AM49. The flocculated medium as nutrients for subsequent algal cultivation was also tested. Consecutive treatment with 8.5mM CaCl2 and 0.2mM FeCl3 as coagulants and 1% bioflocculant from the culture broth of P. polymyxa AM49 showed the highest flocculating activity of up to 95% for high density algal cultures. The medium flocculated with the coagulants and bioflocculant showed less than 8% decrease in the growth yield in the subsequent algal cultivation. Furthermore, a 20% or 50% fresh BG11 medium supplement allowed the flocculated medium to maintain a high growth yield in subsequent algal cultivation. These results suggest that the flocculation method presented here is efficient and bio-friendly, and allows the reuse of the flocculated medium, thereby contributing to the economic cultivation and harvest of microalgae. [ABSTRACT FROM AUTHOR]

Microalgae, including cyanobacteria and eukaryotic algae, are hotspots of primary production and play a critical role in global carbon cycling. However, these species often form blooms that poses a threat to aquatic ecosystems. Although the use of bacteria-derived cyanocides is regarded as an environmentally friendly method for controlling cyanobacterial blooms, only a few studies have examined their potential impact on ecosystems. This study is the first to explore the response of particle-attached (PA) and free-living (FL) bacteria to the dynamics of microalgal communities induced by the biological cyanocide paucibactin A. The microalgal community dynamics were divided into two distinct phases [phase I (days 0–2) and phase II (days 3–7)]. In phase I, paucibactin A caused a sudden decrease in the cyanobacterial concentration. Phase II was characterized by increased growth of eukaryotic microalgae (Scenedesmus , Pediastrum , Selenastrum , and Coelastrum). The stability of the bacterial community and the contribution of stochastic processes to community assembly were more pronounced in phase II than in phase I. The microalgal dynamics triggered by paucibactin A coincided with the succession of the PA and FL bacterial communities. The lysis of cyanobacteria in phase I favored the growth of microbial organic matter degraders in both the PA (e.g., Aeromonas and Rheinheimera) and FL (e.g., Vogesella) bacterial communities. In phase II, Lacibacter , Phycisphaeraceae , and Hydrogenophaga in the PA bacterial community and Lacibacter , Peredibacter , and Prosthecobacter in the FL bacterial community showed increased relative abundances. Overall, the FL bacterial community exhibited greater sensitivity to the two sequential processes compared with the PA bacterial community. These results highlight the need for studies evaluating the impact of biological cyanocides on aquatic ecosystems when used to control natural cyanobacterial blooms. [Display omitted] • Microalgal community dynamics caused by paucibactin A were divided into two phases. • Microalgal community dynamics caused the succession of bacterial community. • PA bacteria were more stable than FL bacteria in response to microalgal dynamics. • The lysis of cyanobacteria promoted eukaryotic microalgal growth. • Cyanobactericidal process enhanced bacterial interactions in the network. [ABSTRACT FROM AUTHOR]

Slow growth is the major obstacle in the production of astaxanthin in Haematococcus lacustris. Introduction of a "red cell inoculation system (RCIS)" reduced the culture time of H. lacustris by 43% by increasing its growth rate and inducing the earlier synthesis of astaxanthin. Red mature H. lacustris cells rather than green cyst cells were re-inoculated to decrease the growth period from 7 to 4 days by producing more zoospore cells. Starved red cells could take up nutrients quickly, thereby achieving faster growth. To further shorten the astaxanthin induction time, FeSO4, NaCl, and NaHCO3 were added to the cells, and their effects were compared. These chemicals accelerated astaxanthin biosynthesis, decreasing the production period from 7 to 4 days. This study focused on faster astaxanthin production to achieve economic feasibility by RCIS and chemical cues. Fast-track growth and a synthesis induction strategy enabled a more economic and efficient production of astaxanthin in H. lacustris. [ABSTRACT FROM AUTHOR]

Despite widespread use as a preservation method, cryopreservation remains recalcitrant for microalgae preservation due to low viability and strain specificity. Herein, a cryopreservation method for Ettlia sp. YC001 was optimized using the following strategies. Cold acclimation at 4 °C for 24 h prior to the freezing procedure enhanced the expression of the cold response pathway and heat-shock proteins, helping to both stabilize the proteins against cold stress and prevent rapid dehydration. Three independent parameters of cryopreservation, the cooling rate, plunge temperature, and thawing temperature, were optimized with various cryoprotectants using a response surface methodology (RSM). Finally, the cellular damage was minimized when using the optimized controlled cooling procedure with an accurate programmable freezer. When applying the optimized conditions, the cell viability of the cryopreserved strain YC001 was > 90% after 1 year. It is believed that the suggested approach can also be applied to other commercial microalgal strains. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Self-flocculating Ettlia sp. has high extracellular protein/carbohydrate ratio (EPS P /EPS C). • Growth-promoting and flocculation-inducing bacterial groups were detected. • Filamentous EPS matrices connecting cells appeared exclusively in xenic culture. • More compact EPS structure was introduced by the bacterial community. • Bacteria was not decisive but facilitating factor for Ettlia flocculation. Abstract This study examined the effects of a bacterial community and extracellular polymeric substances (EPS) on Ettlia sp. flocculation. The growth rate, flocculation efficiency (FE), bacterial community, and EPS profile of axenic and xenic Ettlia cultures were monitored during 46 days of cultivation. For the xenic culture, with a great abundance of growth-promoting and flocculation-inducing bacteria, the biomass density was 18.75% higher and its FE reached 100% in the mid-stationary phase. Moreover, microscopic observation and a quantitative analysis of the EPS revealed the exclusive presence of long filamentous EPS and more compact structure in the xenic Ettlia culture, possibly explaining its better FE. Notwithstanding, for the axenic culture, despite a lower biomass density and reduced abundance of EPS, its FE reached 92.54% in the mid-stationary phase. Thus, the role of the bacterial community was found to be supportive rather than vital for the high settleability of the self-flocculating Ettlia microalgal culture. [ABSTRACT FROM AUTHOR]

Incorporation of wastewater from industrial sectors into the design of microalgal biorefineries has significant potential for advancing the practical application of this emerging industry. This study tested various food industrial wastewaters to assess their suitability for microalgal cultivation. Among these wastewaters, defective soy sauce (DSS) and soy sauce wastewater (SWW) were chosen but DSS exhibited the highest nutrient content with 13,500 ppm total nitrogen and 3051 ppm total phosphorus. After diluting DSS by a factor of 50, small-scale cultivation of microalgae was conducted to optimize culture conditions. SWW exhibited optimal growth at 25–30 °C and 300–500 μE m−2 s−1, while DSS showed optimal growth at 30–35 °C. Based on a 100-mL lab-scale and 3-L outdoor cultivation with an extended cultivation period, DSS outperformed SWW, exhibiting higher final biomass productivity. Additionally, nutrient-concentrated nature of DSS is advantageous for transportation at an industrial scale, leading us to select it as the most promising feedstock for microalgal cultivation. With further optimization, DSS has the potential to serve as an effective microalgal cultivation feedstock for large-scale biomass production. [Display omitted] • Multiple food wastewaters were collected and evaluated for microalgal culture • Defective soy sauce (DSS) showed the highest microalgal growth • Less than 50-fold dilution of DSS negatively influenced photosynthesis • Outdoor cultivation using 50-fold diluted DSS resulted in 0.27 g L−1 d−1 of biomass productivity [ABSTRACT FROM AUTHOR]

The increased inputs of nutrients have been demonstrated to be a major contributing factor to the eutrophication of lakes and reservoirs which can lead to the production of harmful algal/cyanobacterial blooms and deleteriously affect the aesthetics of water-bodies. Floating plant-culture systems have been widely used for the ecological remediation of eutrophic water in a cost-effective manner. We investigated the applicability of Korean japonica rice variety ‘Nampyeong’ in a floating-culture system in a eutrophic lake for nutrient uptake and biomass production. Chemical and organic compound compositions were analyzed two times during the growth stages of the rice plant: 98 DAT (days after transplanting) and 165 DAT. Total nitrogen and phosphorus contributed around 1.36 and 0.15 (% dry weight), respectively, in rice plant components at 165 DAT. Crude protein, lipids, fiber and ash were 4.35, 1.91, 23.66 and 5.55 (% dry weight), respectively. In addition, microcystin levels in the rice plant components ranged from 0.0008 to 0.002 μg/g and did not exceed the recommended tolerable limits. These results suggested that the developed floating rice-culture system showed a good potential as a holistic management approach in terms of nutrient reduction, rice production for further use as feed and for bloom control. [ABSTRACT FROM AUTHOR]

Nostoc sp. NK (KCTC 12772BP) was isolated and cultivated in a BG11 medium and a nitrate-free BG11 medium (BG11 0 ). To enhance C-phycocyanin (C-PC) content in the cells, different fluorescent lamps (white, plant, and red) were used as light sources for complementary chromatic adaptation (CCA). The maximum biomass productivity was 0.42 g/L/d and 0.32 g/L/d under BG11 and BG11 0 conditions, respectively. The maximum C-PC contents were 8.4% (w/w) under white lamps, 13.6% (w/w) under plant lamps, and 18% (w/w) under BG11 0 and the red light condition. The maximum C-PC productivity was 57.4 mg/L/d in BG11 0 under the red lamp condition. These results indicate that a higher C-PC content could be obtained under a diazotrophic condition and a CCA reaction. The C-PC could be released naturally from cells without any extraction processes, when Nostoc sp. NK was cultivated in the BG11 0 medium with CO 2 aeration and put in dark conditions at 5 °C. [ABSTRACT FROM AUTHOR]

Global warming and eutrophication accelerated Microcystis blooms, causing water quality deterioration. Cyanocides produced by cyanobactericidal bacteria have attracted substantial attention for controlling Microcystis blooms owing to their environmental friendliness. However, their application is still in the early stages, highlighting the need for the discovery of novel cyanocides. Herein, we isolated and purified a novel macrocyclic tambjamine produced by Paucibacter aquatile DH15, named paucibactin A. The cyanocidal activity of paucibactin A (1 μg/mL) against Microcystis (106 cells/mL) was 81.6% after 24 h of exposure. Paucibactin A killed Microcystis by destroying its structural integrity, photosynthetic and antioxidant systems, and macromolecules. The expression of the key genes involved in these fundamental processes in Microcystis was downregulated after paucibactin A treatment. In a microcosm study, paucibactin A (1 μg/mL) exhibited selective cyanobactericidal activity against Microcystis and Dolichospermum but not against other cyanobacteria. However, 87.4% of paucibactin A was degraded by photolysis in 24 h. Cyanobactericidal processes promoted the growth of eukaryotic microalgae, possibly by altering the competitive relationship and inducing changes in the bacterial community and interaction network. Collectively, our findings suggest that paucibactin A could be an effective cyanobactericidal compound for controlling Microcystis and Dolichospermum blooms. [Display omitted] • The first report of a macrocyclic tambjamine with cyanobactericidal activity. • Paucibactin A is a novel cyanocide for controlling both Microcystis and Dolichospermum blooms. • Paucibactin A destroys photosystems and induces oxidative stress in Microcystis. • Paucibactin A is degraded quickly after bloom removal, leaving no secondary pollution. [ABSTRACT FROM AUTHOR]

This study investigated the photoperiodic effects on the biomass production and nutrient removal in the algal–bacterial wastewater treatment, under the following three conditions: (1) a natural 12 h:12 h LD cycle, (2) a dark-elongated 12 h:60 h LD cycle, and (3) a two-phase photoperiodic 12 h:60 h LD, followed by 12 h:12 h LD cycles. The two-phase photoperiodic operation showed the highest dry cell weight and lipid productivity (282.6 mg L −1 day −1 , 71.4 mg L −1 day −1 ) and most efficient nutrient removals (92.3% COD, 95.8% TN, 98.1% TP). The genetic markers and sequencing analyses indicated rapid increments of bacteria, subsequent growths of Scenedesmus , and stabilized population balances between algae and bacteria. In addition, the two-phase photoperiod provided a higher potential for the algal–bacterial consortia to utilize various organic carbon substrates. [ABSTRACT FROM AUTHOR]

The establishment of an axenic culture of microalgae is essential step in understanding its physiology, genetics, and ecology. However, culturing of microalgae is usually accompanied by complex and variable associated prokaryotic and eukaryotic microorganisms. Conventional approaches used for obtaining axenic cultures of microalgae are time-consuming and often involve difficulties in maintaining and preserving axenicity. In this study, we developed a procedure for establishing an axenic culture of Ettlia sp. YC001 and demonstrate that we maintained the axenic culture through subculture in the long term. Three sequential treatments, an antibiotic cocktail, serial dilution, and plate spreading, were applied to strain YC001 and we confirmed axenicity using molecular and physiological methods. The bacterial community associated with strain YC001 was investigated to select antibiotics for their specific elimination. The xenic culture (1 × 10 cells/mL) was treated with the antibiotic cocktail-5 (AC-5), carbendazim, chloramphenicol, imipenem, rifampicin, and tetracycline for 3 days, followed by serial dilution up to 1 × 102 cells and spreading on agar plates. The pure colonies were analyzed using denaturing gradient gel electrophoresis (DGGE), fluorescence-activated cell sorting (FACS), and scanning electron microscopy (SEM). The procedure we developed can be applied to other strains of microalgae for the establishment of axenic cultures. [ABSTRACT FROM AUTHOR]

Algae based wastewater treatment coupled to biofuel production has financial benefits and practical difficulties. This study evaluated the factors influencing diversity and growth of indigenous algal consortium cultivated on untreated municipal wastewater in a high rate algal pond (HRAP) for a period of 1 year using multivariate statistics. Diversity analyses revealed the presence of Chlorophyta , Cyanophyta and Bacillariophyta . Dominant microalgal genera by biovolume in various seasons were Scenedesmus sp., Microcystis sp., and Chlorella sp. Scenedesmus sp., persisted throughout the year but none of three strains co-dominated with the other. The most significant factors affecting genus dominance were temperature, inflow cyanophyta and organic carbon concentration. Cyanophyta concentration affected microalgal biomass and diversity, whereas temperature impacted biomass. Preferred diversity of microalgae is not sustained in wastewater systems but is obligatory for biofuel production. This study serves as a guideline to sustain desired microalgal consortium in wastewater treatment plants for biofuel production. [ABSTRACT FROM AUTHOR]

[Display omitted] • The colony-forming ability of Microcystis contributes to Microcystis blooms. • Microcystis colony mainly consists of Microcystis , associated microbes, and EPS. • Understanding colony formation is critical to develop novel strategies for bloom control. • Application of Microcystis -microbes interaction in bioremediation and production of useful materials Microcystis sp., amongst the most prevalent bloom-forming cyanobacteria, is typically found as a colonial form with multiple microorganisms embedded in the mucilage known as extracellular polymeric substance. The colony-forming ability of Microcystis has been thoroughly investigated, as has the connection between Microcystis and other microorganisms, which is crucial for colony development. The following are the key subjects to comprehend Microcystis bloom in depth: 1) key issues related to the Microcystis bloom, 2) features and functions of extracellular polymeric substance, as well as diversity of associated microorganisms, and 3) applications of Microcystis -microorganisms interaction including bloom control, polluted water bioremediation, and bioactive compound production. Future research possibilities and recommendations regarding Microcystis -microorganism interactions and their significance in Microcystis colony formation are also explored. More information on such interactions, as well as the mechanism of Microcystis colony formation, can bring new insights into cyanobacterial bloom regulation and a better understanding of the aquatic ecosystem. [ABSTRACT FROM AUTHOR]

Haematococcus lacustris is a chlamydomonadalean with high biotechnological interest owing to its capacity to produce astaxanthin, a valuable secondary carotenoid with extraordinary antioxidation properties. However, its prolonged growth has limited its utility commercially. Thus, rapid growth to attain high densities of H. lacustris cells optimally producing astaxanthin is an essential biotechnological target to facilitate profitable commercialisation. Our study focused on characterising the bacterial communities associated with the alga's phycosphere by metagenomics. Subsequently, we altered the bacterial consortia in combined co-culture with key beneficial bacteria to optimise the growth of H. lacustris. The algal biomass increased by up to 2.1-fold in co-cultures, leading to a 1.6-fold increase in the astaxanthin yield. This study attempted to significantly improve the H. lacustris growth rate and biomass yield via Next-Generation Sequencing analysis and phycosphere bacterial augmentation, highlighting the possibility to overcome the hurdles associated with astaxanthin production by H. lacustris at a commercial scale. • Upscaling of the production of AX is driven by boosting the growth of microalga. • The Sphingomonas -ASV1 was strongly correlated with the growth of H. lacustris. • The algal biomass was increased to 2.1-folds higher than the control group. • The biosynthesis of AX was expressed 1.6-folds higher than the control group. • Bacterial interaction with alga demonstrated excellent reproducibility in NGS. [ABSTRACT FROM AUTHOR]