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A novel rod-shaped, Gram-stain-negative bacterial strain MS17T was obtained from a co-culture of Microcystis aeruginosa and Myriophyllum spicatum. The examination of the 16S ribosomal RNA gene sequence showed a significant degree of similarity between strain MS17T and Paucibacter sediminis S2-9T (98.4%), Roseateles violae PFR6T (98.1%), ‘Roseateles cellulosilyticus’ P8T (98.0%), Roseateles aquae APW11T (97.9%), Roseateles oligotrophus CHU3T (97.7%), Roseateles saccharophilus DSM 654T (97.6%), Kinneretia aquatilis CR182T (97.7%), Pelomonas aquatica CCUG 52575T (97.6%), and Roseateles toxinivorans 2C20T (97.0%). Between strain MS17T and the type strains of closely related species, digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) values were below 21.9% and 78.48%. The respiratory quinone was ubiquinone Q-8. The main fatty acids (> 10.0%) were C15:1ω6c, C16:0, C17:0, and summed feature 3 (C16:1ω7c and/or C16:1ω6c). The polar lipids comprised phosphatidylethanolamine, unidentified phospholipid, phosphatidylglycerol, unidentified aminophospholipid, unidentified aminolipid, and three unidentified lipids. The genomic G + C content was 65.9%. According to phenotypic characteristics, phylogenetic relationships, and chemotaxonomic data, strain MS17T has been categorized as a newly discovered species belonging to the Roseateles genus, and the name Roseateles microcysteis sp. nov. is suggested. It exhibits distinct biochemical properties that differentiate it from closely related species. The type strain is MS17T (=KCTC 8001T = LMG 33142T). [ABSTRACT FROM AUTHOR]

A novel Gram-negative, white-pigmented, and auxin-producing strain, 20NA77.5T, was isolated from fresh water during cyanobacterial bloom period. Pairwise comparison of the 16S rRNA gene sequences showed that strain 20NA77.5T belonged to the genus Undibacterium and exhibited the highest sequence similarity to the type strains of Undibacterium danionis (98.00%), Undibacterium baiyunense (97.93%), Undibacterium macrobrachii (97.92%), and Undibacterium fentianense (97.71%). The average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between strain 20NA77.5T and its related type strains were below 79.93 and 23.80%, respectively. The predominant fatty acids (> 10% of the total fatty acids) were C16:0 and summed feature 3 (C16:1ω7c and/or C16:1ω6c). The genomic DNA G + C content of strain 20NA77.5T was found to be 48.61%. Based on the phylogenetic distinctness, chemotaxonomic features, and phenotypic features, strain 20NA77.5T is considered to represent a novel species of the genus Undibacterium, for which the name Undibacterium cyanobacteriorum sp. nov is proposed. The type strain is 20NA77.5T (= KCTC 8005T = LMG 33136T). [ABSTRACT FROM AUTHOR]

A novel Gram-negative, white-pigmented, and auxin-producing strain, 20NA77.5T, was isolated from fresh water during cyanobacterial bloom period. Pairwise comparison of the 16S rRNA gene sequences showed that strain 20NA77.5T belonged to the genus Undibacterium and exhibited the highest sequence similarity to the type strains of Undibacterium danionis (98.00%), Undibacterium baiyunense (97.93%), Undibacterium macrobrachii (97.92%), and Undibacterium fentianense (97.71%). The average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values between strain 20NA77.5T and its related type strains were below 79.93 and 23.80%, respectively. The predominant fatty acids (> 10% of the total fatty acids) were C16:0 and summed feature 3 (C16:1ω7c and/or C16:1ω6c). The genomic DNA G + C content of strain 20NA77.5T was found to be 48.61%. Based on the phylogenetic distinctness, chemotaxonomic features, and phenotypic features, strain 20NA77.5T is considered to represent a novel species of the genus Undibacterium, for which the name Undibacterium cyanobacteriorum sp. nov is proposed. The type strain is 20NA77.5T (= KCTC 8005T = LMG 33136T). [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]

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]

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]

Background: The major goals of monitoring aquatic animals are to understand ecosystem health status and to identify signals of environmental change and pollution. Over the past few decades, advances in individual omics technology have been expanded to aquatic ecotoxicology and health assessment. The single-omics approach has produced one type of result, but recently, the combined multi-omics approach has enabled depiction of multidimensional datasets for holistic interpretation regarding the molecular responses of biological systems. Objective: In this mini review, the power of the multi-omics approach for monitoring the health of freshwater animals is described, along with a discussion on challenges and the current limitations in the complexity of integrating multidimensional datasets. Results: Recent studies have suggested that the aquatic ecotoxicology field can benefit significantly using multi-omics platforms; however, the examples of multi-omics applications remain limited. The complex metabolism underlying the sensitivity, health status, response, tolerance, and adaptation of certain aquatic organisms can be uncovered through comprehensively integrated omics results and advanced bioinformatics. Conclusion: Multi-omics approaches can provide crucial datasets for developing multidimensional biomarkers and deciphering novel biological insights into aquatic ecotoxicology and health assessments. This platform provides a novel opportunity for environmental scientists to connect the biological responses and chemical data in aquatic organisms exposed to environmental challenges. [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]

Background: Monitoring microbial communities especially focused on pathogens in newly developed wastewater treatment systems is recommended for public health. Thus, we investigated the microbial community shift in a pilot-scale microalgal treatment system for piggery wastewater. Results: Microalgae showed reasonable removal efficiencies for COD and ammonia, resulting in higher transparency of the final effluent. Metagenome and microbial diversity analyses showed that heterotrophic microalgal cultivation barely changed the bacterial community; however, the mixotrophic microalgal cultivation induced a sudden change. In addition, an evaluation of risk groups (RGs) of bacteria showed that raw piggery wastewater included abundant pathogens, and the microalgal treatment of the raw piggery wastewater decreased the RG2 pathogens by 63%. However, co-cultivation of microalgae and the most dominant RG2 pathogen, Oligella, showed no direct effects between them. Conclusions: Thus, a microbial interaction network was constructed to elucidate algae-bacteria interrelationships, and the decrease in Oligella was indirectly connected with microalgal growth via Brevundimonas, Sphingopyxis, and Stenotrophomonas. In a validation test, 3 among 4 connecting bacterial strains exhibited inhibition zones against Oligella. Therefore, we showed that microalgal wastewater treatment causes a decrease in RG2 bacteria, which is an indirect impact of microalgae associated with bacteria. 9xuCqXStUBwsH8dUwtqkoY Video abstract [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]

In recent decades, harmful algal blooms (HABs) have been significantly affecting environments, aquatic ecosystems, and human health, as well as damaging economies, especially near rivers and lakes, and in coastal regions. Microcystis and Anabaena are two genera of harmful cyanobacteria that will often predominate during toxic microalgal blooms. In this study, we employ a method for control and mitigation of HABs by microalgal cell instability using different types of aminoclays (ACs). Allelopathic interactions between the two strains of algae are studied in mono-culture, co-culture, and filtrated cell-free medium in the presence of the ACs. The growth of the Anabaena strain is significantly reduced by the cyanobacterial strains in the co-culture media, and both are significantly affected by the Acs'-enhanced algicidal activity. Anabaena sp. KVSF7 shows higher sensitivity against the ACs than does Microcystis sp. KW. In this way, the algicidal activity of ACs is harnessed, the effects of which are in the order of aluminum aminoclay (AlAC) > magnesium aminoclay (MgAC) > calcium aminoclay (CaAC). The ammonium sites in the ACs carry positive charges to induce instability of HABs along with the electrostatic attraction between algal cells and AC. Therefore, the utilization of the algicidal activity of the ACs can effectively reduce HABs, especially on cyanobacterial blooms. [ABSTRACT FROM AUTHOR]

Summary: Biological control agents including microbes and their products have been studied as sustainable crop protection strategies. Although aquatic microalgae have been recently introduced as a biological control agent, the underlying molecular mechanisms are largely unknown. The aim of the present study was to investigate the molecular mechanisms underlying biological control by microalga Chlorella fusca. Foliar application of C. fusca elicits induced resistance in Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000 that activates plant immunity rather than direct antagonism. To understand the basis of C. fusca‐triggered induced resistance at the transcriptional level, we conducted RNA sequencing (RNA‐seq) analysis. RNA‐seq data showed that, upon pathogen inoculation, C. fusca treatment primed the expression of cysteine‐rich receptor‐like kinases, WRKY transcription factor genes, and salicylic acid and jasmonic acid signalling‐related genes. Intriguingly, the application of C. fusca primed pathogen‐associated molecular pattern ‐triggered immunity, characterized by reactive oxygen species burst and callose deposition, upon flagellin 22 treatment. The attempts to find C. fusca determinants allowed us to identify d‐lactic acid secreted in the supernatant of C. fusca as a defence priming agent. This is the first report of the mechanism of innate immune activation by aquatic microalga Chlorella in higher plants. Significance Statement: Aquatic microalgae have been recently used as bioprotectants and biostimulants in crop plants; however, the underlying molecular mechanism remains unclear. Here, we demonstrate for the first time that the priming of PAMP‐triggered immunity induced by the aquatic microalgae Chlorella fusca against Pseudomonas syringae pv. tomato DC3000 in land plant Arabidopsis. [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]

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]

To elucidate the interspecies connectivity between cyanobacteria and other bacteria (non-cyanobacteria) during cyanobacterial harmful algal blooms (cyanoHABs), samples were collected from the Nakdong River, Korea, from June 2016 to August 2017, and microbial recurrent association network (MRAN) analysis was performed to overcome the limitations of conventional network analysis. Microcystis blooms were tightly linked with Pseudanabaena in summer and were accompanied by significant changes in the non-cyanobacterial community composition (nCCC) compared to non-bloom period. Riverine bacterial communities could be clearly separated into modules that were involved in the formation, maintenance, and decomposition of cyanoHABs. Roseomonas and Herbaspirillum were directly linked with major cyanobacteria and assigned to connector and module hub in cyanoHABs-related modules, respectively. The functional profiles of the cyanoHABs-related modules suggested that nitrate reduction, aerobic ammonia oxidation, fermentation, and hydrocarbon degradation could be increased during the Microcystis bloom periods. In conclusion, MRAN analysis revealed that specific bacteria belonging to cyanoHABs-related module, including connectors and module hubs, appeared to contribute to the development and collapse of cyanoHABs. Therefore, to understand cyanoHABs, a modular microbial perspective may be more helpful than a single bacterial species perspective. [ABSTRACT FROM AUTHOR]

A novel Gram-stain negative, rod-shaped and motile bacterial strain, designated strain Seoho-38T, was isolated from a eutrophic lake in South Korea. Polyphasic taxonomic studies were performed to investigate the taxonomic position of the new isolate. The phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain Seoho-38T formed a distinct cluster with Nevskia ramosa Soe1T, Nevskia persephonica G6M-30T, Nevskia soli GR15-1T, Nevskia terrae KIS13-15T and Nevskia aquatilis F2-63T with bootstrap resampling value of 100%. Of those Nevskia strains, the new isolate shows high sequence similarity with N. ramosa Soe1T (98.7%) and N. persephonica G6M-30T (97.2%), and values lower than 96.5% with the other type strains. The new isolate was observed to grow aerobically in 0–1.5% (w/v) NaCl (optimum 0%), at pH 7.0–9.0 (optimum pH 7.0) and temperature 15–36 °C (optimum 20–30 °C) on R2A medium. DNA–DNA relatedness values between strain Seoho-38T and the type strains of reference species in the genus Nevskia were < 24%. The genomic DNA G + C content was determined to be 67.4 mol%. Ubiquinone-8 (Q-8) (95%) and ubiquinone-7 (Q-7) (5%) were identified as the respiratory quinones. The cellular polar lipids were identified as diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, a phosphoaminolipid, two glycolipids, an aminolipid and four unidentified lipids. The major fatty acid components were found to include summed feature 3 (C16:1ω7c and/or C16:1ω6c), summed feature 8 (C18:0ω7c and/or C18:0ω6c), C16:0 and C14:0. Based on the above polyphasic evidence, strain Seoho-38T (= KCTC 52221T = JCM 31888T) represents a new species of the genus Nevskia, for which the name Nevskia lacus sp. nov. is proposed. [ABSTRACT FROM AUTHOR]

A polyphasic taxonomic study was carried out on strains PB105T and PB108 isolated from a grass soil in Korea. The cells of the strains were Gram-stain negative, non-spore-forming, non-motile, and rod-shaped. Comparative 16S rRNA gene sequence studies showed a clear affiliation of these strains with Bacteroidetes, which showed high pairwise sequence similarities with Hymenobacter algoricola VUG-A23aT (99.2%), Hymenobacter fastidiosus VUG-A124aT (97.4%), and Hymenobacter daecheongensis Dae14T (96.9%). The phylogenetic analysis based on 16S rRNA gene sequences showed that the strains formed a clear phylogenetic lineage with the genus Hymenobacter. The major fatty acids were identified as C15:0 iso, C15:0 anteiso, C16:1ω5c, C15:0 iso 3-OH, C17:0 iso 3-OH, summed feature 3 (C16:1ω6c and/or C16:1ω7c/t), and summed feature 4 (C17:1 anteiso B and/or C17:1 iso I). The major cellular polar lipids were identified as phosphatidylethanolamine, an unidentified aminolipid, and two unidentified lipids. The respiratory quinone was identified as MK-7 and the genomic DNA G+C content was determined to be 64.5 mol% for strain PB105T and 64.1 mol% for strain PB108. DNA-DNA hybridization value of type strain PB105T with H. algoricola VUG-A23aT was 32.3% (reciprocal 39.2). Based on the combined genotypic and phenotypic data, we propose that strains PB105T and PB108 represent a novel species of the genus Hymenobacter, for which the name Hymenobacter daejeonensis sp. nov. is proposed. The type strain is PB105T (= KCTC 52579T = JCM 31885T). [ABSTRACT FROM AUTHOR]

Microorganisms have the tendency to accumulate at interfaces through the release of extracellular polymeric substances to form aggregates such as films or flocs. This physical association leads to different modes of interactions among cells and the subsequent development of functionally and metabolically diverse consortia. Aggregation of cells in aqueous suspensions often results in the formation of flocs, which are hotspots of enhanced microbial processes. This has important implications for the dynamics of organic and inorganic matter in varied ecosystems. These microbial flocs are not only important components in nutrient turnover, decomposition, and sinking flux but also facilitate contaminant removal and treatment of wastewater and biomass harvesting. Greater insight into the multitude of interactions between microorganisms in flocs would be useful to enhance the efficiency of bioflocculation processes. This review covers the fundamental aspects and outlines the role of bioflocculation in controlled industrial processes and in nature. [ABSTRACT FROM AUTHOR]

A novel Gram-negative, rod-shaped and motile bacterial strain, designated strain M36, was isolated from a culture of a bloom-forming cyanobacterium, Microcystis sp., collected from a eutrophic lake in Korea. Its taxonomic position was investigated by using a polyphasic taxonomic approach. The isolate was found to grow aerobically at 15-42 °C (optimum 25 °C), pH 7.0-11.0 (optimum pH 8.0) and in the presence of 0-1.0% (w/v) NaCl (optimum 0% NaCl) on R2A medium. The phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain M36 is closely related to Acidovorax anthurii DSM 16745 (98.1%), Acidovorax konjaci DSM 7481 (97.7%) and Acidovorax avenae DSM 7227 (97.0%) and also formed a clear phylogenetic lineage with other Acidovorax species. DNA-DNA relatedness between strain M36 and the closely related species of the genus Acidovorax was <30%. The major fatty acid components identified included summed feature 3 (C ω7 c and/or C ω6 c), C and summed feature 8 (C ω7 c and/or C ω6 c). The DNA G+C content of strain M36 was determined to be 66.8 mol%. Based on above polyphasic evidence, strain M36 is concluded to represent a new species of genus Acidovorax, for which the name Acidovorax lacteus sp. nov. is proposed. The type strain is M36 (=KCTC 52220 = JCM 31890). [ABSTRACT FROM AUTHOR]

A polyphasic taxonomic study was carried out on strain EBR-8-1 isolated from a biofilm reactor in Korea. The cells of the strain were Gram-stain negative, non-spore-forming, non-motile, and short rod-shaped. Comparative 16S rRNA gene sequence studies showed a clear affiliation of this strain with Betaproteobacteria, which showed high pairwise sequence similarities with Pusillimonas noertemannii BN9 (99.1 %), Pusillimonas soli MJ07 (97.3 %), Pusillimonas ginsengisoli DCY25 (97.2 %), and Pusillimonas harenae B201 (96.8 %). The phylogenetic analysis based on 16S rRNA gene sequences showed that the strain formed a clear phylogenetic lineage within the genus Pusillimonas. The major fatty acids were identified as C, C cyclo and C cyclo ω8 c. The major cellular polar lipids were identified as phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and an unidentified aminolipid. The respiratory quinone was identified as Q-8 and the genomic DNA G+C content was determined to be 63.3 mol%. On the basis of polyphasic evidence, it is proposed that strain EBR-8-1 should be placed in a new species, Pusillimonas caeni sp. nov. The type stain is EBR-8-1 (=KCTC 42353 = JCM 30463). [ABSTRACT FROM AUTHOR]

Roles of nutrients and other environmental variables in development of cyanobacterial bloom and its toxicity are complex and not well understood. We have monitored the photoautotrophic growth, total microcystin concentration, and microcystins synthetase gene (mcyA) expression in lab-grown strains of Microcystis NIES 843 (reference strain), KW (Wangsong Reservoir, South Korea), and Durgakund (Varanasi, India) under different nutrient regimes (nitrogen, phosphorus, and boron). Higher level of nitrogen and boron resulted in increased growth (avg. 5 and 6.5 Chl a mg/L, resp.), total microcystin concentrations (avg. 1.185 and 7.153 mg/L, resp.), and mcyA transcript but its expression was not directly correlated with total microcystin concentrations in the target strains. Interestingly, Durgakund strain had much lower microcystin content and lacked microcystin-YR variant over NIES 843 and KW. It is inferred that microcystin concentration and its variants are strain specific. We have also examined the heterotrophic bacteria associated with cyanobacterial bloom in Durgakund Pond and Wangsong Reservoir which were found to be enriched in Alpha-, Beta-, and Gammaproteobacteria and that could influence the bloom dynamics. [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]

Bloom-forming freshwater cyanobacterial genera pose a major ecological problem due to their ability to produce toxins and other bioactive compounds, which can have important implications in illnesses of humans and livestock. Cyanobacteria such as Microcystis, Anabaena, Oscillatoria, Phormidium, and Aphanizomenon species producing microcystins and anatoxin-a have been predominantly documented from most South Korean lakes and reservoirs. With the increase in frequency of such blooms, various monitoring approaches, treatment processes, and prediction models have been developed in due course. In this paper we review the field studies and current knowledge on toxin producing cyanobacterial species and ecological variables that regulate toxin production and bloom formation in major rivers (Han, Geum, Nakdong, and Yeongsan) and reservoirs in South Korea. In addition, development of new, fast, and high-throughput techniques for effective monitoring is also discussed with cyanobacterial bloom advisory practices, current management strategies, and their implications in South Korean freshwater bodies. [ABSTRACT FROM AUTHOR]

A Gram-negative, aerobic, non-motile, and rod-shaped bacterium, designated strain DS48-5-3, was isolated from a 48 m sediment sample taken from Daechung Reservoir, Republic of Korea. Comparative 16S rRNA gene sequence studies showed a clear affiliation of this strain to the Bacteroidetes, notably most closely related to Ferruginibacter alkalilentus HU1-GD23, Ferruginibacter lapsinanis HU1-HG42 and Ferruginibacter yonginensis HME8442, showing 16S rRNA gene sequence similarities to the type strains of these species of 95.2-96.4 % similarity. The predominant ubiquinone was identified as MK-7. The major fatty acids were identified as iso-C, iso-C 3-OH, and iso-C G. The G+C content of the genomic DNA of strain DS48-5-3 was determined to be 37.2 %. On the basis of polyphasic evidence, it is proposed that strain DS48-5-3 should belong to a novel species, for which the name Ferruginibacter profundus sp. nov. (type strain DS48-5-3 = KCTC 32478 = JCM 19431), is proposed. [ABSTRACT FROM AUTHOR]

Biodiesel from microalgae is recognized as a desirable, renewable biofuel to replace petroleum-derived transport fuels. However, the efficient harvesting of microalgae is a major hurdle for commercialization. Therefore, the development of a cost-effective harvesting method is essential to reduce production cost. A partial factorial design was used to screen the main factors involved, which were the concentration of FeCl, the bioflocculant, and the time of slow mixing. Response surface methodology (RSM) was used to further investigate the optimal conditions for these factors on flocculation of Botryococcus braunii. Analysis of variance and other relevant tests confirmed the validity of the suggested model. The optimal conditions inferred from the obtained equation were 0.79 mM FeCl, 0.58 % ( v/ v) bioflocculant, and 180 sec of slow mixing for 1.1 g DCW L of B. braunii. The flocculating activity under these conditions was 90.6 %. By using RSM, the optimal conditions for flocculation of B. braunii could be reached more quickly and efficiently. [ABSTRACT FROM AUTHOR]

Spirulina platensis, a filamentous cyanobacterium, produces γ-linolenic acid (GLA, 18:3), which is an important anti-inflammatory for pharmaceutical use. Thus, to increase the GLA content in S. platensis, this study investigated the combined effect of a light-dark (LD) two-stage culture and mixotrophic culture including a precursor of GLA. When compared with a photoautotrophic culture, the supplement of a GLA precursor, such as a long- or short-chain carbon source, enhanced the total fatty acid and GLA contents in the cells in the two-stage culture. The highest GLA content of 2% ( w/ w) and productivity of 27.6 ± 4.7 mg L were obtained in S. platensis when using 0.01 mM palmitic acid as a supplement in the two-stage culture. This study also suggests that a mixotrophic and LD two-stage culture may represent a method for increasing the total lipid production, which can then be converted to biofuels. [ABSTRACT FROM AUTHOR]

abstract: Background: Hemodialysis (HD) patients with functional iron deficiency often develop resistance to recombinant human erythropoietin (rhEPO). Recent studies have shown that intravenous ascorbic acid (IVAA) administration could override rhEPO resistance in HD patients. This study was undertaken to test the effects of IVAA in HD patients with normoferritinemic functional iron deficiency accompanied by EPO-hyporesponsive anemia. Methods: Fifty-eight HD patients with normoferritinemic anemia (between 100 and 500μg/L) were included and divided into the control (N=25) and IVAA (N=33) groups. IVAA patients received 500mg of IVAA with each dialysis session for 3 months and an additional 4-month follow-up after the end of the therapy. Results: Twenty patients had a response to IVAA with a significant increase in hemoglobin level (Hgb>1.0g/dL) and reduction of weekly rhEPO dosage compared with the control group after 3 months of treatment (P<0.05). Compared with non-responders, transferrin saturation (TSAT) was significantly decreased in the responders group (26±11 vs. 35±14%, P<0.05) on baseline data. There was a significant increase in serum iron and TSAT (baseline vs. 3 months, serum iron 57±22 vs. 108±22μg/dL, TSAT 26±11 vs. 52±7%, P<0.05) and a decrease in serum ferritin (377±146 vs. 233±145ng/mL, P<0.05) in the responders group (N=20), but no significant changes in the control and non-responders groups (N=13) at 3-month treatment. Conclusion: IVAA can be a potent and effective adjuvant therapy for HD patients with rhEPO-resistant normoferritinemic anemia. In addition, IVAA can reduce the dosage of rhEPO for anemia correction. [Copyright &y& Elsevier]

The influence of nitrogen (N) deficiency on the cell growth and intracellular lipid production of the alga Botryococcus braunii UTEX 572 was investigated. Biomass concentration and lipid content of B. braunii cultivated in modified Chu-13 medium containing 0.04, 0.37, and 3.66 mM nitrate were 0.23-0.38 g L and 36-63% of dry cell weight, respectively. The specific growth rate of B. braunii reached a constant of 0.185 day during cultivation with an initial nitrate feed of 3.66 mM. The maximum lipid content of B. braunii was 63% with 0.04 mM nitrate. However, the maximum lipid productivity of 0.019 g L day was achieved with 0.37 mM nitrate. The level of oleic acid, an important component of biodiesel, was higher at 86% of the total fatty acids under N-limited conditions (0.04 mM nitrate) compared to 69% under N-sufficient conditions (3.66 mM nitrate). Furthermore, expression of the stearoyl-ACP desaturase gene ( sad) encoding a stearoyl-ACP desaturase involved in the synthesis of oleic acid was 2.6-fold higher under N-limited conditions than under N-sufficient conditions. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms are a common issue in eutrophic freshwaters, and some cyanobacteria produce toxins, threatening the health of humans and livestock. Microcystin, a representative cyanobacterial hepatotoxin, is frequently detected in most Korean lakes and reservoirs. This study developed predictive models for cyanobacterial bloom using artificial neural networks (ANNs; self-organizing map [SOM] and multilayer perceptron [MLP]), including an evaluation of related environmental factors. Fourteen environmental factors, as independent variables for predicting the cyanobacteria density, were measured weekly in the Daechung Reservoir from spring to autumn over 5 years (2001, 2003-2006). Cyanobacterial density was highly associated with environmental factors measured 3 weeks earlier. The SOM model was efficient in visualizing the relationships between cyanobacteria and environmental factors, and also for tracing temporal change patterns in the environmental condition of the reservoir. And the MLP model exhibited a good predictive power for the cyanobacterial density, based on the environmental factors of 3 weeks earlier. The water temperature and total dissolved nitrogen were the major determinants for cyanobacteria. The water temperature had a stronger influence on cyanobacterial growth than the nutrient concentrations in eutrophic waters. Contrary to general expectations, the nitrogen compounds played a more important role in bloom formation than the phosphorus compounds. [ABSTRACT FROM AUTHOR]

Different sampling methods can often produce different results when cyanobacterial blooms are intense and there are surface scums. Accordingly, five commonly used sampling methods and four sampling times were compared for monitoring of Oscillatoria and Microcystis populations. The different methods and times led to significantly different results for cyanobacterial biomass and its variance. Sampling methods that tended to be more specific to surface scums resulted in much higher and more variable measurements. Although sampling later in the day greatly reduced variances, the measured biomass was much lower than at earlier times of day, which was attributed to cyanobacterial downward migration in the afternoon. These trends were common for Oscillatoria and Microcystis. In order to overcome such problems, the median and median absolute deviation (MAD) were proposed, instead of the arithmetic mean and standard deviation (SD), for presenting a central tendency of measured values. Although the mean ± SD has been widely used to express a central tendency, it is too sensitive to outlying values that are very common during cyanobacterial blooms. The large differences in the mean values between the sampling methods and times were reduced by using the median values. Furthermore, the median ± MAD revealed the real data distribution more effectively. [ABSTRACT FROM AUTHOR]

Of several types of chemical surfactants and biosurfactants, only the culture broth of Bacillus subtilis C1 containing surfactin at 10 mg l-1 completely inhibited the growth of Microcystis aeruginosa, a bloom-forming cyanobacterium in highly eutrophic lakes. The broth with 10 mg surfactin l-1 also removed 85% of the maximally grown M. aeruginosa (chlorophyll-a concentration, 1000 μg l-1) within 2 d, and the removal efficiency was enhanced by Ca2+ over 1 mM. The growth of Anabaena affinis, another bloom-forming cyanobacterium, was also inhibited about 70% with surfactin at 10 mg l-1 broth. However, the effect of the broth was delayed over 3 d in the green algae, Chlorella vulgaris and Scenedesmus sp., and was negligible in a diatom, Navicula sp., indicating the potential for the selective control of cyanobacterial blooms. [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]

Blooms of the ichthyotoxic dinoflagellate Cochlodinium polykrikoides are responsible for massive fish mortality events in Korean coastal waters (KCW). They have been consistently present in southern KCW over the last two decades, but they were not observed in 2016, unlike in the previous years. Despite extensive studies, the cause of this absence of this dinoflagellate bloom remains largely unknown. Thus, we compared physico-chemical and biological data from along the Tongyeong coast between 2016 and the previous four years (2012–2015). The averages of water temperature and salinity in August, 2016 were significantly (p < 0.001) different from those in the previous years. The amount of Changjiang River discharge, which can affect the environmental conditions in the southern Korean coastal area via ocean currents, was larger than in the previous years, resulting in a reduction in the salinity level in August when blooms of C. polykrikoides usually occurred. Moreover, compared to previous years, in 2016, there was a weak expansion of C. polykrikoides blooms in the Goheung-Oenarodo area where C. polykrikoides blooms were annually initiated in KCW. Lastly, the strong winds from the typhoon Lionrock may also have contributed to the early termination of this dinoflagellate bloom. Together with these findings, the combination of these environmental conditions in 2016, unlike in previous years, may have inhibited the formation of C. polykrikoides blooms along the Tongyeong coast. [ABSTRACT FROM AUTHOR]

This genus contains both phototrophs and nonphototrophic members. Here, we present a high-quality complete genome of the strain CHu59-6-5T, isolated from a freshwater sediment. The circular chromosome (4.39 Mbp) of the strain CHu59-6-5T has 64.4% G+C content and contains 4240 genes, of which a total of 3918 genes (92.4%) were functionally assigned to the COG (clusters of orthologous groups) database. Functional genes for denitrification (narGHJI, nirK and qnor) were identified on the genomes of the strain CHu59-6-5T, except for N2O reductase (nos) genes for the final step of denitrification. Genes (soxBXAZY) for encoding sulfur oxidation proteins were identified, and the FSD and soxF genes encoding the monomeric flavoproteins which have sulfide dehydrogenase activities were also detected. Lastly, genes for the assembly of two different RND (resistance-nodulation division) type efflux systems and one ABC (ATP-binding cassette) type efflux system were identified in the Rhodoferax sediminis CHu59-6-5T. Phylogenetic analysis based on 16S rRNA sequences and Average Nucleotide Identities (ANI) support the idea that the strain CHu59-6-5T has a close relationship to the genus Rhodoferax. A polyphasic study was done to establish the taxonomic status of the strain CHu59-6-5T. Based on these data, we proposed that the isolate be classified to the genus Rhodoferax as Rhodoferax sediminis sp. nov. with isolate CHu59-6-5T. [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 microbial community in eutrophic freshwater sediment was investigated from a 67-cm-deep sediment core collected from the Daechung Reservoir in South Korea, where cyanobacterial blooms have occurred annually for the past 30 years. The majority of core sediments were characterized by dark-grayish, fine-grained mud with abundant gas-escaped and thinly laminated layers. Intervals of summer and winter seasons were represented by periodic peaks of geochemical profiles of parameters such as grain size and relative carbon mass ratios to various nutrients such as nitrogen, sulfur, and phosphorus. In bacteria, Proteobacteria (66.6%) was the most prevalent phylum, followed by Chloroflexi (8.9%), Bacteroidetes (5.1%), and Spirochaetes (2.6%). Archaea were also abundant, representing approximately half of the total prokaryotes in the sediments. Notably, three Bacteria (Sulfuricurvum, Sideroxydans, and Gallionella) and one Archaea (Thermoplasmata) accounted for 43.4% and 38.4% of the total bacteria and archaea, respectively, implying that iron and sulfur oxidizing microorganisms dominate in this eutrophic freshwater sediment. These results indicate that 1) eutrophic freshwater lakes in monsoon climates undergo a stratified sedimentary process with seasonal and annual variations in geochemical and microbial profiles, and 2) the microbial oxidative metabolism of iron and sulfur is notably active in sediments from a eutrophic lake. [ABSTRACT FROM AUTHOR]