Sang Eun Jeong

High resolution depth distribution of Bacteria, Archaea, methanotrophs, and methanogens in the bulk and rhizosphere soils of a flooded rice paddy

The communities and abundances of methanotrophs and methanogens, along with the oxygen, methane, and total organic carbon (TOC) concentrations, were investigated along a depth gradient in a flooded rice paddy. Broad patterns in vertical profiles of oxygen, methane, TOC, and microbial abundances were similar in the bulk and rhizosphere soils, though methane and TOC concentrations and 16S rRNA gene copies were clearly higher in the rhizosphere soil than in the bulk soil. Oxygen concentrations decreased sharply to below detection limits at 8 mm depth. Pyrosequencing of 16S rRNA genes showed that bacterial and archaeal communities varied according to the oxic, oxic-anoxic, and anoxic zones, indicating that oxygen is a determining factor for the distribution of bacterial and archaeal communities. Aerobic methanotrophs were maximally observed near the oxic-anoxic interface, while methane, TOC, and methanogens were highest in the rhizosphere soil at 30–200 mm depth, suggesting that methane is produced mainly from organic carbon derived from rice plants and is metabolized aerobically. The relative abundances of type I methanotrophs such as Methylococcus, Methylomonas, and Methylocaldum decreased more drastically than those of type II methanotrophs (such as Methylocystis and Methylosinus) with increasing depth. Methanosaeta and Methanoregula were predominant methanogens at all depths, and the relative abundances of Methanosaeta, Methanoregula, and Methanosphaerula, and GOM_Arc_I increased with increasing depth. Based on contrasts between absolute abundances of methanogens and methanotrophs at depths sampled across rhizosphere and bulk soils (especially millimeter-scale slices at the surface), we have identified populations of methanogens (Methanosaeta, Methanoregula, Methanocella, Methanobacterium, and Methanosphaerula), and methanotrophs (Methylosarcina, Methylococcus, Methylosinus, and unclassified Methylocystaceae) that are likely physiologically active in situ.

Comparative Analysis of Drosophila melanogaster Gut Microbiota with Respect to Host Strain, Sex, and Age

Microbiota has a significant impact on the health of the host individual. The complexity of the interactions between mammalian hosts and their microbiota highlights the value of using Drosophila melanogaster as a model organism, because of its relatively simple microbial community and ease of physiological and genetic manipulation. However, highly variable and sometimes inconsistent results regarding the microbiota of D. melanogaster have been reported for host samples collected from different geographical locations; discrepancies that may be because of the inherent physiological conditions of the D. melanogaster host. Here, we conducted a comparative analysis of the gut microbiota of two D. melanogaster laboratory strains, w1118 and Canton S, with respect to the sex and age of the host, by pyrosequencing of the 16S rRNA gene. In addition to the widespread and abundant commensal bacterial genera Lactobacillus and Acetobacter, we identified Enterococcus and Leuconostoc as major host-strain-specific bacterial genera. The relative proportions of these bacterial genera, and those of the species within each, were found to differ markedly with respect to strain, sex, and age of the host, even though host individuals were reared under the same nutritional conditions. By using various bioinformatic tools, we uncovered several characteristic features of microbiota corresponding to specific categories of the flies: host-sex-bias association of specific bacteria, age-dependent alteration of microbiota across host species and sex, and uniqueness of the microbiota of female w1118 flies. Our results, thus, help to further our understanding of host–microbe interactions in the D. melanogaster model.

Lysobacter aestuarii sp. nov., isolated from estuary sediment.

A Gram-stain-negative, strictly aerobic, non-motile bacterium, designated strain S2-CT, was isolated from an estuary sediment in South Korea and subjected to a polyphasic taxonomic investigation. Cells were catalase- and oxidase-positive rods without gliding motility. Growth of strain S2-CT was observed at 15-40 °C (optimum, 30 °C), at pH 5.5-9.0 (optimum, pH 6.5-7.5) and in the presence of 0-7.0 % (w/v) NaCl (optimum, 0-2 %). Only ubiquinone-8 (Q-8) was detected as the isoprenoid quinone and iso-C16 : 0, iso-C15 : 0, summed feature 9 (comprising iso-C17 : 1ω9c and/or C16 : 0 10-methyl), iso-C11 : 0, iso-C11 : 0 3-OH and iso-C14 : 0 were found to be the major cellular fatty acids. Strain S2-CT contained phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol as the major polar lipids. The G+C content of the genomic DNA was 63.8 mol%. Phylogenetic analysis, based on 16S rRNA gene sequences, revealed that strain S2-CT formed a distinct phyletic lineage within the genus Lysobacter. Strain S2-CT was most closely related to Lysobacter daejeonensis GH1-9T with 97.1 % 16S rRNA gene sequence similarity and the DNA-DNA relatedness value between strain S2-CT and the type strain of L. daejeonensis was 45.7 ± 2.2 %. On the basis of the phenotypic, chemotaxonomic and molecular features, strain S2-CT clearly represents a novel species of the genus Lysobacter, for which the name Lysobacter aestuarii sp. nov. is proposed. The type strain is S2-CT ( = KACC 18502T = JCM 31130T).

Parasphingopyxis algicola sp. nov., isolated from a marine red alga Asparagopsis taxiformis and emended description of the genus Parasphingopyxis Uchida et al. 2012

An aerobic, Gram-stain-negative, yellow-pigmented bacterium, designated strain ATAX6-5T, was isolated from a marine red alga, Asparagopsistaxiformis, in South Korea. Cells were non-motile rods showing catalase- and oxidase-positive reactions. Growth of strain ATAX6-5T was observed at 5-35 °C (optimum, 30 °C), at pH 6.0-9.5 (optimum, pH 7.0) and in the presence of 0-6.0 % (w/v) NaCl (optimum, 2 %). Ubiquinone-10 was detected as the sole isoprenoid quinone and C18 : 1ω7c, C16 : 0 and C17 : 1ω6c were identified as the major cellular fatty acids. Diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, sphingoglycolipid, phosphatidylcholine, an unknown phospholipid and four unknown glycolipids were detected as polar lipids. The G+C content of the genomic DNA was 60.4 mol%. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain ATAX6-5T formed a tight phylogenic lineage with Parasphingopyxis lamellibrachiae JAMH 0132T with a 100 % bootstrap value. Strain ATAX6-5T was most closely related to P. lamellibrachiae JAMH 0132T with a 96.9 % 16S rRNA gene sequence similarity. Based on phenotypic, chemotaxonomic and molecular features, strain ATAX6-5T clearly represents a novel species of the genus Parasphingopyxis, for which the name Parasphingopyxis algicola sp. nov. is proposed. The type strain is ATAX6-5T (=KACC 18993T=JCM 31719T). An emended description of the genus Parasphingopyxis is also proposed.

Roseitalea porphyridii gen. nov., sp. nov., isolated from a red alga, and reclassification of Hoeflea suaedae Chung et al. 2013 as Pseudohoeflea suaedae gen. nov., comb. nov.

A Gram-staining-negative, strictly aerobic bacterial strain, designated MA7-20T, was isolated from a marine alga, Porphyridium marinum, in Korea. Cells showing oxidase-positive and catalase-positive activities were motile rods with bipolar flagella. Growth of strain MA7-20T was observed at 15-45 °C (optimum, 30-37 °C), at pH 6.0-10.5 (optimum, pH 7.0-8.0) and in the presence of 0-7 % (w/v) NaCl (optimum, 2-3 %). Strain MA7-20T contained summed feature 8 (comprising C18 : 1ω7c/C18 : 1ω6c), 11-methyl C18 : 1ω7c and C18 : 0 as the major fatty acids and ubiquinone-10 as the sole isoprenoid quinone. The major polar lipids were phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine and phosphatidyl-N-methylethanolamine. The G+C content of the genomic DNA was 61.5 mol%. Strain MA7-20T was most closely related to Hoeflea suaedae YC6898T, Oricola cellulosilytica CC-AMH-0T and Nitratireductor basaltis J3T with 96.0, 95.8 and 95.8 % 16S rRNA gene sequence similarities, respectively, but the strain formed a distinct phylogenetic lineage from them within the family Phyllobacteriaceae with a low bootstrap value. H. suaedae also formed a clearly distinct phylogenetic lineage from other members of the genus Hoeflea and closely related genera. On the basis of phenotypic, chemotaxonomic and molecular properties, strain MA7-20T represents a novel species of a new genus of the family Phyllobacteriaceae, for which the name Roseitalea porphyridii gen. nov., sp. nov. is proposed. The type strain is MA7-20T (=KACC 18807T=JCM 31538T). In addition, H. suaedae is also reclassified as Pseudohoeflea suaedae gen. nov., comb. nov. (type strain YC6898T=KACC 14911T=NBRC 107700T).

Marinicauda algicola sp. nov., isolated from a marine red alga Rhodosorus marinus

An aerobic Gram-stain-negative prosthecate bacterium, designated RMAR8-3T, was isolated from a marine red alga Rhodosorus marinus in the Republic of Korea. Cells were dimorphic rods with a single polar prostheca (non-motile) or flagellum (motile) showing catalase- and oxidase-positive reactions. Growth of strain RMAR8-3T was observed at 15-45 °C (optimum, 40 °C), at pH 6.0-9.0 (optimum, pH 7.0) and in the presence of 0-10 % (w/v) NaCl (optimum, 2 %). Ubiquinone-10 was detected as the sole isoprenoid quinone and C18 : 0, summed feature 8 (comprising C18 : 1 ω7c and/or C18 : 1ω6c), C17 : 0, C12 : 0 3-OH and C16 : 0 were identified as the major cellular fatty acids. The major polar lipids were sulfo-quinovosyldiacylglycerol, glucuronopyranosyldiglyceride and monoglycosyldiglyceride. The G+C content of the genomic DNA was 66.3 mol%. Strain RMAR8-3T was most closely related to Marinicauda pacifica P-1 km-3T with a 97.6 % 16S rRNA gene sequence similarity. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain RMAR8-3T formed a tight phylogenic lineage with M. pacifica P-1 km-3T within the family Hyphomonadaceae. On the basis of phenotypic, chemotaxonomic and molecular features, strain RMAR8-3T clearly represents a novel species of the genus Marinicauda, for which the name Marinicauda algicola sp. nov. is proposed. The type strain is RMAR8-3T (=KACC 18990T=JCM 31718T).

Pandoraea terrae sp. nov., isolated from forest soil, and emended description of the genus Pandoraea Coenye et al. 2000

A Gram-staining-negative, facultatively aerobic, white-colony-forming bacterium, designated strain SE-S21T, was isolated from forest soil of Jeju Island in Korea. Cells were motile rods with a single polar flagellum, showing catalase- and oxidase-positive reactions. Growth was observed at 10-40 °C (optimum, 30 °C), pH 4.0-10.0 (optimum, pH 7.0-7.5) and with 0-4.0 % (w/v) NaCl (optimum, 0-2 %). Only ubiquinone-8 was detected as the isoprenoid quinone, and C16 : 0, C17 : 0 cyclo, C19 : 1ω8c cyclo and summed feature 2 (comprising C12 : 0 aldehyde and/or unknown) were found to be the major fatty acids. Phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, an unknown aminophospholipid, an unknown aminolipid and an unknown lipid were detected as the major polar lipids. Putrescine and 2-hydroxyputrescine were the predominant polyamines. The DNA G+C content was 61.0 mol%. Phylogenetic analyses based on 16S rRNA and DNA gyrase B gene sequences revealed that strain SE-S21T formed a phyletic lineage within the genus Pandoraea. Strain SE-S21T was most closely related to Pandoraea faecigallinarum KOxT and Pandoraea pnomenusa CCUG 38742T with 98.8 % and 98.7 % 16S rRNA gene sequence similarities, respectively. However, the DNA-DNA relatedness values between strain SE-S21T and the type strains of P. faecigallinarum and P. pnomenusa were 26.6±5.7 % and 20.5±3.7 %, respectively. On the basis of phenotypic, chemotaxonomic and molecular features, strain SE-S21T clearly represents a novel species of the genus Pandoraea, for which the name Pandoraea terrae sp. nov. is proposed. The type strain is SE-S21T (=KACC 18127T=JCM 30137T). An emended description of the genus Pandoraea is also proposed.

Celeribacter naphthalenivorans sp. nov., a naphthalene-degrading bacterium from tidal flat sediment.

A Gram-stain-negative, aerobic and moderately halophilic bacterium, designated strain EMB201(T), was isolated from tidal flat sediment of the South Sea in Korea. Cells were motile rods with a single polar flagellum and had catalase- and oxidase-positive activities. Growth of strain EMB201(T) was observed at 15-37 °C (optimum, 30 °C), at pH 5.0-9.5 (optimum, pH 7.0-7.5) and in the presence of 1-7% (w/v) NaCl (optimum, 2-3%). Strain EMB201(T) contained ubiquinone-10 as the sole isoprenoid quinone and summed feature 8 (comprising C18 : 1ω7c/ω6c), C18 : 0ω7c 11-methyl and C10 : 0 3-OH as the major fatty acids. Phosphatidylglycerol and an unidentified amino lipid were identified as the major polar lipids and an unidentified phospholipid and three unidentified lipids were detected as minor components. The G+C content of the genomic DNA was approximately 58.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain EMB201(T) formed a phylogenetic lineage with members of the genus Celeribacter. Strain EMB201(T) was related most closely to Celeribacter halophilus ZXM137(T) with a 16S rRNA gene sequence similarity of 98.3%, and the level of DNA-DNA relatedness between the two strains was 17.0 ± 2.0%. The combined chemotaxonomic and molecular properties suggest that strain EMB201(T) represents a novel species of the genus Celeribacter, for which the name Celeribacter naphthalenivorans sp. nov. is proposed. The type strain is EMB201(T) ( = KACC 18393(T) = JCM 30679(T)).

Niveitalea solisilvae gen. nov., sp. nov., isolated from forest soil and emended description of the genus Flavihumibacter Zhang et al. 2010.

A Gram-stain-negative and strictly aerobic bacterial strain, designated 6-4T, was isolated from forest soil in Jeju island, South Korea. Cells showing oxidase-positive and catalase-negative reactions were thin and long non-motile rods. Growth of strain 6-4T was observed at 20-35 °C (optimum, 30 °C) and pH 6.0-9.0 (optimum, pH 7.0). Strain 6-4T contained iso-C15 : 0, anteiso-C15 : 0, iso-C15 : 1 G and iso-C17 : 0 3-OH as the major fatty acids and menaquinone-7 (MK-7) as the sole isoprenoid quinone. Phosphatidylethanolamine was the major polar lipid and five unidentified aminolipids, one unidentified aminophospholipid and one unidentified lipid were also detected as minor polar lipids. The G+C content of the genomic DNA was 45.8 mol%. Strain 6-4T was most closely related to Flavihumibacter solisilvae 3-3T with a low 16S rRNA gene sequence similarity (94.2 %) and phylogenetic analysis indicated that the strain formed a distinct phylogenetic lineage from members of the genus Flavihumibacter and other closely related genera. On the basis of phylogenetic inference and phenotypic, chemotaxonomic and molecular properties, strain 6-4T represents a novel species of a new genus of the family Chitinophagaceae, for which the name Niveitalea solisilvae gen. nov., sp. nov. is proposed. The type strain of Niveitalea solisilvae is 6-4T (=KACC 18808T=JCM 31525T). An emended description of the genus Flavihumibacter is also proposed.

Genomic and metabolic features of the Bacillus amyloliquefaciens group– B. amyloliquefaciens, B. velezensis, and B. siamensis– revealed by pan-genome analysis

The genomic and metabolic features of the Bacillus amyloliquefaciens group comprising B. amyloliquefaciens, B. velezensis, and B. siamensis were investigated through a pan-genome analysis combined with an experimental verification of some of the functions identified. All B. amyloliquefaciens group genomes were retrieved from GenBank and their phylogenetic relatedness was subsequently investigated. Genome comparisons of B. amyloliquefaciens, B. siamensis, and B. velezensis showed that their genomic and metabolic features were similar; however species-specific features were also identified. Energy metabolism-related genes are more enriched in B. amyloliquefaciens, whereas secondary metabolite biosynthesis-related genes are enriched in B. velezensis. Compared to B. amyloliquefaciens and B. siamensis, B. velezensis harbors more genes in its core-genome which are involved in the biosynthesis of antimicrobial compounds, as well as genes involved in d-galacturonate and d-fructuronate metabolism. B. amyloliquefaciens, B. siamensis, and B. velezensis all harbor a xanthine oxidase gene cluster (xoABCDE) in their core-genomes that is involved in metabolizing xanthine and uric acid to glycine and oxalureate. A reconstruction of B. amyloliquefaciens group metabolic pathways using their individual pan-genomes revealed that the B. amyloliquefaciens group strains have the ability to metabolize diverse carbon sources aerobically, or anaerobically, and can produce various metabolites such as lactate, ethanol, acetate, CO2, xylitol, diacetyl, acetoin, and 2,3-butanediol. This study therefore provides insights into the genomic and metabolic features of the B. amyloliquefaciens group.