Mesorhizobium microcysteis sp. nov., isolated from a culture of Microcystis aeruginosa.

Strain MaA-C15T, a Gram-stain-negative, non-spore-forming and strictly aerobic bacterium, was isolated from a xenic culture of Microcystis aeruginosa in the Republic of Korea. Cells were motile rods showing positive reactions in catalase and oxidase tests. Growth was observed between 15 and 37 °C (optimum, 30 °C), between pH 6.0 and pH 11.0 (optimum, pH 7.5) and in the presence of 0-2.0 % (w/v) NaCl (optimum, 0 %). Strain MaA-C15T contained C16 : 0, 11-methyl-C18 : 1 ω7c, cyclo-C19 : 0 ω8c and summed feature 8 (C18 : 1 ω6c and/or C18 : 1 ω7c) as the major cellular fatty acids and ubiquinone-10 as the sole respiratory quinone. Phosphatidylethanolamine, phosphatidylmonomethylethanolamine, an unidentified aminophospholipid, an unidentified glycolipid and three unidentified phospholipids were detected as the major polar lipids. The G+C content of the genomic DNA was 64.1 mol%. Phylogenetic and phylogenomic analyses based on 16S rRNA gene and genome sequences revealed that strain MaA-C15T formed a phyletic lineage with Mesorhizobium sediminum YIM M12096T within the family Phyllobacteriaceae. Strain MaA-C15T was most closely related to Mesorhizobium albiziae DSM 21822T with a 98.2 % 16S rRNA sequence similarity. Average nucleotide identity and in silico DNA-DNA hybridization values between strain MaA-C15T and M. albiziae DSM 21822T were 75.4 and 20.1 %, respectively. Based on the results of phenotypic, chemotaxonomic and molecular analyses, strain MaA-C15T represents a novel species of the genus Mesorhizobium, for which the name Mesorhizobium microcysteis sp. nov. is proposed. The type strain is MaA-C15T (=KACC 21226T=JCM 33503T).

Paenibacillus agri sp. nov., isolated from soil.

A strict aerobic bacterium, strain JW14T was isolated from soil in the Republic of Korea. Cells were Gram-stain-positive, non-endospore-forming and motile rods showing catalase-positive and oxidase-negative activities. Growth of strain JW14T was observed at 20-37 °C (optimum, 30 °C), pH 6.0-10.0 (optimum, pH 7.0) and in the presence of 0-2.0% NaCl (optimum, 0%). Strain JW14T contained menaquinone-7 as the sole isoprenoid quinone, anteiso-C15:0, C16:0 and iso-C16 : 0 as the major fatty acids (>10.0%), and diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, three unidentified aminophospholipids and an unidentified lipid as the major polar lipids. The cell-wall peptidoglycan of strain JW14T contained meso-diaminopimelic acid. The DNA G+C content of strain JW14T calculated from the whole genome sequence was 48.1 mol%. Strain JW14T was most closely related to Paenibacillus graminis DSM 15220T with 97.4% 16S rRNA gene sequence similarity. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain JW14T formed a distinct phyletic lineage from closely related type strains within the genus Paenibacillus. Based on the results of phenotypic, chemotaxonomic and molecular analyses, strain JW14T represents a novel species of the genus Paenibacillus, for which the name Paenibacillus agri sp. nov. is proposed. The type strain is JW14T (=KACC 21840T=JCM 34279T).

Nonlabens ponticola sp. nov., isolated from seawater and reclassification of Nonlabens sediminis as a later heterotypic synonym of Nonlabens tegetincola.

A Gram-stain-negative, orange-pigmented and strictly aerobic bacterium, designated strain MJ115T, was isolated from seawater in Pohang, South Korea. Cells were non-motile rods and showed positive reactions for catalase and oxidase tests. Growth of strain MJ115T was observed at 4-35 °C (optimum, 30 °C), pH 6.0-7.0 (optimum, pH 6.5) and in the presence of 0-8.0 % (w/v) NaCl (optimum, 2.0%). Strain MJ115T contained iso-C15 : 0, anteiso-C15 : 0, anteiso-C17 : 1 ω9c, C17 : 0 2-OH, iso-C16 : 0 3-OH, iso-C17 : 0 3-OH and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) as major cellular fatty acids and menaquinone-6 as the major respiratory quinone. Phosphatidylethanolamine, two unidentified aminolipids and four unidentified lipids were detected as major polar lipids. The G+C content of the genomic DNA was 40.7 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain MJ115T formed a phyletic lineage with Nonlabens marinus S1-08T, Nonlabens agnitus JC2678T and Nonlabens antarcticus AKS 622T within the genus Nonlabens. Strain MJ115T was also most closely related to N. marinus S1-08T, N. agnitus JC2678T and N. antarcticus AKS 622T with 96.5, 96.4 and 96.0 % 16S rRNA sequence similarities, respectively. Here it is proposed that strain MJ115T represents a new species of the genus Nonlabens, for which the name Nonlabens ponticola sp. nov. is proposed. The type strain is MJ115T (=KCTC 72237T=NBRC 113963T). In addition, the comparison of the whole genome sequences and phenotypic features suggested that Nonlabens tegetincola and Nonlabens sediminis belong to the same species. Therefore, it is proposed that N. sediminis is reclassified as a later heterotypic synonym of N. tegetincola.

Flavobacterium microcysteis sp. nov., isolated from a culture of Microcystis aeruginosa.

A Gram-stain-negative, yellow-pigmented, strictly aerobic bacterium, designated strain MaA-Y11T, was isolated from a culture of Microcystis aeruginosa in the Republic of Korea. Cells were non-motile rods showing catalase- and oxidase-positive reactions. Growth of strain MaA-Y11T was observed at 25-37 °C (optimum, 30 °C) and pH 6.0-9.0 (optimum, 7.0) and in the presence of 0-1.0 % (w/v) NaCl (optimum, 0 %). Strain MaA-Y11T did not produce flexirubin-type pigments. Strain MaA-Y11T contained iso-C15 : 0, iso-C17 : 0 3-OH and summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) as major cellular fatty acids and menaquinone-6 as the sole isoprenoid quinone. Phosphatidylethanolamine, three unidentified aminolipids and four unidentified lipids were detected as the major polar lipids. The G+C content of the genomic DNA was 37.0 mol%. Phylogenetic analysis, based on 16S rRNA gene sequences, showed that strain MaA-Y11T formed a phyletic lineage with Flavobacterium lindanitolerans IP-10T within the genus Flavobacterium. Strain MaA-Y11T was most closely related to Flavobacterium lindanitolerans IP-10T, with a 98.85 % 16S rRNA gene sequence similarity, and shared less than 93.87 % sequence similarities with other type strains. Average nucleotide identity and in silico DNA-DNA hybridization values between strain MaA-Y11T and the type strain of F. lindanitolerans were 87.0 and 32.3 %, respectively. Here, we conclude that strain MaA-Y11T represents a new species of the genus Flavobacterium, for which the name Flavobacterium microcysteis sp. nov. is proposed. The type strain is MaA-Y11T (=KACC 21225T=JCM 33501T).

Mucilaginibacter agri sp. nov. and Mucilaginibacter humi sp. nov., isolated from soil.

Two Gram-stain-negative, facultative anaerobic and non-motile bacteria, strains R11T and S1162T, were isolated from soil in the Republic of Korea. Both strains were catalase- and oxidase-positive and contained menaquinone-7 as the major isoprenoid quinone. Strain R11T contained summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), iso-C15:0, C16:0 and iso-C17:0 3-OH as major fatty acids and phosphatidylethanolamine, an unidentified aminophospholipid and an unidentified aminolipid as major polar lipids; while strain S1162T contained summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), iso-C15:0, iso-C17:0 3-OH, C16:0 and summed feature 9 (10-methyl C16:0 and/or iso-C17:1 ω9c) as major fatty acids and phosphatidylethanolamine and an unidentified aminophospholipid as major polar lipids. The DNA G+C contents of strains R11T and S1162T calculated from their whole genomes were 42.7 and 42.9 mol%, respectively. Results of phylogenetic analysis based on 16S rRNA gene sequences showed that strain R11T formed a phylogenetic lineage with Mucilaginibacter jinjuensis YC7004T and strain S1162T formed a distinct phyletic lineage from closely related type strains within the genus Mucilaginibacter. Strains R11T and S1162T were most closely related to M. jinjuensis YC7004T and Mucilaginibacter panaciglaebae BXN5-31T with 97.78 and 97.23% 16S rRNA gene sequence similarities, respectively. On the basis of phenotypic, chemotaxonomic and molecular analysis, strains R11T and S1162T represent two novel species of the genus Mucilaginibacter, for which the names Mucilaginibacter agri sp. nov. and Mucilaginibacter humi sp. nov. are proposed, respectively. The type strains of M. agri and M. humi are R11T (=KACC 21228T=JCM 33472T) and S1162T (=KACC 21669T=JCM 33916T), respectively.

Flavihumibacter soli sp. nov., Isolated from Soil.

A novel Gram-stain-positive, strictly aerobic, non-motile, rod-shaped bacterium, designated strain R14T was isolated from steep grove soil and taxonomically characterized using a polyphasic approach. Cells showed oxidase-negative and catalase-positive activities and grew at 25-37 °C (optimum, 30 °C), pH 5.0-8.0 (optimum, pH 6.5), and in the presence of 0-0.5% (w/v) NaCl (optimum, 0%). Phylogenetic trees based on 16S rRNA gene sequences revealed that strain R14T formed a phylogenetic lineage with Flavihumibacter genus members within the family Chitinophagaceae. Comparison of 16S rRNA gene sequences showed that strain R14T shared highest similarities with Flavihumibacter solisilvae 3-3T (97.5%), Flavihumibacter petaseus NBRC 106054T (96.7%), and Flavihumibacter stibioxidans YS-17T (96.1%). The G+C content of strain R14T calculated from its whole genome sequence was 44.6 mol%. Strain R14T contained menaquinone-7 and iso-C15:0, iso-C17:0 3-OH, C16:0, C15:1 ω6c, and iso-C15:0-G as the sole respiratory isoprenoid quinone and major cellular fatty acids, respectively. Major polar lipids consisted of phosphatidylethanolamine, two unidentified aminolipids, and four unidentified lipids. Based on phylogenetic, phenotypic, and chemotaxonomic characteristics of strain R14T, it could be concluded that strain R14T represents a novel species of the genus Flavihumibacter, for which the name Flavihumibacter soli sp. nov. is proposed. The type strain is R14T (=KACC 21229T = JCM 33473T).

Linear Six-Carbon Sugar Alcohols Induce Lysis of Microcystis aeruginosa NIES-298 Cells.

Cyanobacterial blooms are a global concern due to their adverse effects on water quality and human health. Therefore, we examined the effects of various compounds on Microcystis aeruginosa growth. We found that Microcystis aeruginosa NIES-298 cells were lysed rapidly by linear six-carbon sugar alcohols including mannitol, galactitol, iditol, fucitol, and sorbitol, but not by other sugar alcohols. Microscopic observations revealed that mannitol treatment induced crumpled inner membrane, an increase in periplasmic space, uneven cell surface with outer membrane vesicles, disruption of membrane structures, release of intracellular matter including chlorophylls, and eventual cell lysis in strain NIES-298, which differed from the previously proposed cell death modes. Mannitol metabolism, antioxidant-mediated protection of mannitol-induced cell lysis by, and caspase-3 induction in strain NIES-298 were not observed, suggesting that mannitol may not cause organic matter accumulation, oxidative stress, and programmed cell death in M. aeruginosa. No significant transcriptional expression was induced in strain NIES-298 by mannitol treatment, indicating that cell lysis is not induced through transcriptional responses. Mannitol-induced cell lysis may be specific to strain NIES-298 and target a specific component of strain NIES-298. This study will provide a basis for controlling M. aeruginosa growth specifically by non-toxic substances.