Abundant iron and sulfur oxidizers in the stratified sediment of a eutrophic freshwater reservoir with annual cyanobacterial blooms.

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.

Mucilaginibacter pocheonensis sp. nov., with ginsenoside-converting activity, isolated from soil of a ginseng-cultivating field.

A Gram-reaction-negative, aerobic, heterotrophic, non-motile, non-spore-forming, rod-shaped bacterial strain, designated Gsoil 032T, was isolated from soil of a ginseng field in Pocheon Province, South Korea, and its taxonomic position was investigated by using a polyphasic approach. Strain Gsoil 032T grew at 10-42 °C and at pH 5.0-10.0 on R2A agar medium. Strain Gsoil 032T possessed ß-glucosidase activity, which was responsible for its ability to transform ginsenoside Rb1 (one of the dominant active components of ginseng) to compound K. On the basis of 16S rRNA gene sequence similarity, strain Gsoil 032T was shown to belong to the family Sphingobacteriaceae and to be related to Mucilaginibacter sabulilitoris SMS-12T (97.6 % sequence similarity) and Mucilaginibacter lappiensis ANJLI2T (97.1 %) The G+C content of the genomic DNA was 44.4 mol%. The predominant respiratory quinone was menaquinone MK-7 and the major fatty acids were summed feature 3 (comprising C16 : 1ω6c and/or C16 : 1ω7c), iso-C15 : 0 and iso-C17 : 0 3-OH. The major polar lipid detected was phosphatidylethanolamine, while the minor polar lipids were various unidentified aminophospholipids, unidentified phospholipids and unidentified polar lipids. DNA and chemotaxonomic data supported the affiliation of strain Gsoil 032T to the genus Mucilaginibacter. Strain Gsoil 032T could be differentiated genotypically and phenotypically from recognized species of the genus Mucilaginibacter. The isolate therefore represents a novel species, for which the name Mucilaginibacter pocheonensis sp. nov. is proposed, with the type strain Gsoil 032T (=KCTC 12641T=LMG 23495T).

Sphingomonas ginsengisoli sp. nov. and Sphingomonas sediminicola sp. nov.

Two novel bacteria, designated strains Gsoil 634(T) and Dae 20(T), were isolated in South Korea from soil of a ginseng field and freshwater sediment, respectively and were characterized by a polyphasic approach to clarify their taxonomic positions. Phylogenetic analysis based on 16S rRNA gene sequences indicated that, although they probably represented two distinct species (indicated by a sequence similarity of 96.6 %), both strain Gsoil 634(T) and strain Dae 20(T) belonged to the genus Sphingomonas and were most closely related to 'Sphingomonas humi' PB323 (97.8 % and 96.7 % sequence similarity, respectively), Sphingomonas kaistensis PB56(T) (96.8 % and 96.7 %), Sphingomonas astaxanthinifaciens TDMA-17(T) (96.6 % and 95.4 %) and Sphingomonas jaspsi TDMA-16(T) (95.6 % and 95.8 %). For both novel strains, the major ubiquinone was Q-10, the major polyamine was homospermidine, the major cellular fatty acids included summed feature 7 (C(18 : 1)ω7c, C(18 : 1)ω9t and/or C(18 : 1)ω12t), C(17 : 1)ω6c and C(16 : 0), and the polar lipids included sphingoglycolipid. These chemotaxonomic data supported the affiliation of both strains to the genus Sphingomonas. However, the DNA-DNA relatedness value between strain Gsoil 634(T) and 'Sphingomonas humi' PB323(T) was 31 %. Moreover, the results of physiological and biochemical tests allowed the phenotypic differentiation of strains Gsoil 634(T) and Dae 20(T) from established members of the genus Sphingomonas. Based on these data, the two isolates represent two novel species in the genus Sphingomonas, for which the names Sphingomonas ginsengisoli sp. nov. (type strain Gsoil 634(T) = KCTC 12630(T) = DSM 18094(T) = LMG 23739(T)) and Sphingomonas sediminicola sp. nov. (type strain Dae 20(T)  = KCTC 12629(T) = DSM 18106(T) = LMG 23592(T)) are proposed.

Streptomyces panacagri sp. nov., isolated from soil of a ginseng field.

A Gram-positive, spore-forming, aerobic actinomycete, strain Gsoil 519T, was isolated from soil of a ginseng field of Pocheon province in South Korea. The closest phylogenetic relatives were Streptomyces marinus Sp080513GE-26T (97.94 % 16S rRNA gene sequence similarity), Streptomyces albiaxialis NRRL B-24327T (97.84 %), Streptomyces albus subsp. albus DSM 40313T (97.84 %), Streptomyces almquistii NBRC 13015T (97.81 %), Streptomyces gibsonii NBRC 15415T (97.81 %), Streptomyces rangoonensis NBRC 13078T (97.81 %), Streptomyces sodiiphilus YIM 80305T (97.77 %) and Streptomyces flocculus NBRC 13041T (97.67 %). The G+C content of the genomic DNA was 71.8 mol%. The chemotaxonomic data [MK-9(H6) and MK-9(H8) as the major menaquinones; ll-diaminopimelic acid as a component of the cell-wall peptidoglycan; ribose, xylose, mannose and glucose as the major cell-wall sugars; and anteiso-C15:0, iso-C15:0, iso-C17:0, anteiso-C17:0 and C16:0 as the major fatty acids] supported the affiliation of strain Gsoil 519T to the genus Streptomyces. The physiological and biochemical characteristics and the low level of DNA-DNA relatedness differentiated the isolate genotypically and phenotypically from recognized members of the genus Streptomyces. The isolate, therefore, represents a novel species, for which the name Streptomyces panacagri sp. nov. is proposed, with Gsoil 519T (=KCTC 19139T=DSM 41871T) as the type strain.

Identification and characterization of a novel Terrabacter ginsenosidimutans sp. nov. beta-glucosidase that transforms ginsenoside Rb1 into the rare gypenosides XVII and LXXV.

A new beta-glucosidase from a novel strain of Terrabacter ginsenosidimutans (Gsoil 3082(T)) obtained from the soil of a ginseng farm was characterized, and the gene, bgpA (1,947 bp), was cloned in Escherichia coli. The enzyme catalyzed the conversion of ginsenoside Rb1 {3-O-[beta-D-glucopyranosyl-(1-2)-beta-D-glucopyranosyl]-20-O-[beta-D-glucopyranosyl-(1-6)-beta-D-glucopyranosyl]-20(S)-protopanaxadiol} to the more pharmacologically active rare ginsenosides gypenoside XVII {3-O-beta-D-glucopyranosyl-20-O-[beta-D-glucopyranosyl-(1-6)-beta-D-glucopyranosyl]-20(S)-protopanaxadiol}, gypenoside LXXV {20-O-[beta-v-glucopyranosyl-(1-6)-beta-D-glucopyranosyl]-20(S)-protopanaxadiol}, and C-K [20-O-(beta-D-glucopyranosyl)-20(S)-protopanaxadiol]. A BLAST search of the bgpA sequence revealed significant homology to family 3 glycoside hydrolases. Expressed in E. coli, beta-glucosidase had apparent K(m) values of 4.2 +/- 0.8 and 0.14 +/- 0.05 mM and V(max) values of 100.6 +/- 17.1 and 329 +/- 31 micromol x min(-1) x mg of protein(-1) against p-nitrophenyl-beta-D-glucopyranoside and Rb1, respectively. The enzyme catalyzed the hydrolysis of the two glucose moieties attached to the C-3 position of ginsenoside Rb1, and the outer glucose attached to the C-20 position at pH 7.0 and 37 degrees C. These cleavages occurred in a defined order, with the outer glucose of C-3 cleaved first, followed by the inner glucose of C-3, and finally the outer glucose of C-20. These results indicated that BgpA selectively and sequentially converts ginsenoside Rb1 to the rare ginsenosides gypenoside XVII, gypenoside LXXV, and then C-K. Herein is the first report of the cloning and characterization of a novel ginsenoside-transforming beta-glucosidase of the glycoside hydrolase family 3.

Rhodanobacter ginsenosidimutans sp. nov., isolated from soil of a ginseng field in South Korea.

A novel gammaproteobacterium, designated Gsoil 3054(T), was isolated from soil of a ginseng field in Pocheon province, South Korea, and was characterized using a polyphasic approach to determine its taxonomic position. The strain was Gram-negative, aerobic, non-motile, non-spore-forming and rod-shaped. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain belonged to the genus Rhodanobacter; it was most closely related to Rhodanobacter fulvus Jip2(T) and Rhodanobacter thiooxydans LCS2(T) (97.9 and 97.2 % 16S rRNA gene sequence similarity, respectively). Chemotaxonomic data, i.e. Q-8 as the predominant ubiquinone and iso-C(15 : 0), 10-methyl C(16 : 0) and iso-C(17 : 0) as major fatty acids, also supported classification of strain Gsoil 3054(T) in the genus Rhodanobacter. However, DNA-DNA hybridization values of Gsoil 3054(T) with R. fulvus Jip2(T) and R. thiooxydans LCS2(T) were 45 and 31 %, respectively. Moreover, physiological and biochemical tests enabled strain Gsoil 3054(T) to be differentiated phenotypically from other established species of Rhodanobacter. Therefore, the isolate represents a novel species, for which the name Rhodanobacter ginsenosidimutans sp. nov. is proposed; the type strain is Gsoil 3054(T) (=KACC 12822(T) =DSM 21013(T) =KCTC 22231(T) =LMG 24457(T)).

Olivibacter soli sp. nov., Olivibacter ginsengisoli sp. nov. and Olivibacter terrae sp. nov., from soil of a ginseng field and compost in South Korea.

Three novel strains, designated Gsoil 034T, Gsoil 060T and Jip13T, isolated from soil from a ginseng field and compost in South Korea, were characterized using a polyphasic approach to clarify their taxonomic positions. These isolates were found to be Gram-negative, aerobic and heterotrophic, non-spore-forming, non-motile and rod-shaped. Phylogenetic analysis based on 16S rRNA gene sequences indicated that these three isolates formed a cluster with the monospecific genus Olivibacter within the family Sphingobacteriaceae but were clearly separated from Olivibacter sitiensis. The 16S rRNA gene sequence similarities between these isolates and the type strain of O. sitiensis were in the range 88.5-90.1 %. Phenotypic and chemotaxonomic data (MK-7 as the major isoprenoid quinone and iso-C15 : 0 2-OH and/or C16 : 1omega7c, iso-C15 : 0 and iso-C17 : 0 3-OH as the major fatty acids) supported the affiliation of these strains to the genus Olivibacter. However, the results of physiological and biochemical tests allowed phenotypic differentiation of the isolates from Olivibacter species with validly published names. Therefore strains Gsoil 034T, Gsoil 060T and Jip13T represent three novel species of the genus Olivibacter, for which the names Olivibacter soli sp. nov. (type strain Gsoil 034T =KCTC 12645T =LMG 23492T), Olivibacter ginsengisoli sp. nov. (type strain Gsoil 060T =KCTC 12646T =LMG 23491T) and Olivibacter terrae sp. nov. (type strain Jip13T =KCTC 12644T =LMG 23494T) are proposed.

Segetibacter koreensis gen. nov., sp. nov., a novel member of the phylum Bacteroidetes, isolated from the soil of a ginseng field in South Korea.

A novel strain, designated Gsoil 664(T), isolated from the soil of a ginseng field in South Korea, was characterized by a polyphasic approach to clarify its taxonomic position. The isolate was Gram-negative, strictly aerobic, heterotrophic, non-motile, non-spore-forming and possessed rod-shaped cells. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the novel isolate formed a cluster with several uncultured bacterial clones and with the established genera Terrimonas, Niastella and Chitinophaga in the phylum Bacteroidetes. However, the isolate was clearly separated from these genera: the gene sequence similarities with respect to the type strains of recognized species from closely related genera ranged from 86.7 to 90.7 %. The G+C content of the genomic DNA was 40.4 mol%. The predominant isoprenoid quinone was MK-7. The major fatty acids were iso-C(15 : 0), iso-C(17 : 0) 3-OH, iso-C(15 : 1) and C(16 : 1) omega 5c. The results of physiological and biochemical tests allowed the genotypic and phenotypic differentiation of strain Gsoil 664(T) from recognized species of related genera. On the basis of the polyphasic evidence, Gsoil 664(T) represents a novel genus and species, for which the name Segetibacter koreensis gen. nov., sp. nov. is proposed. The type strain of S. koreensis is Gsoil 664(T) (=KCTC 12655(T)=DSM 18137(T)).

Chitinophaga ginsengisegetis sp. nov. and Chitinophaga ginsengisoli sp. nov., isolated from soil of a ginseng field in South Korea.

Two novel strains belonging to the phylum Bacteroidetes [formerly the Cytophaga-Flexibacter-Bacteroides (CFB) group], designated Gsoil 040(T) and Gsoil 052(T), were isolated from the soil of a ginseng field in Pocheon province, South Korea. A polyphasic approach was used to characterize the taxonomic position of the novel strains. Both strains were Gram-negative, aerobic, non-motile, non-spore-forming and rod-shaped. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the novel isolates belong to the genus Chitinophaga but are clearly separated from the recognized species of this genus; gene sequence similarities between the novel isolates and type strains of recognized species ranged from 91.2 to 96.5 %. One exception was found; strain Gsoil 052(T) and the type strain of Chitinophaga filiformis had a gene sequence similarity of 99.6 % but had a DNA-DNA relatedness value of 38 %. Phenotypic and chemotaxonomic data (major menaquinone, MK-7; major fatty acids, iso-C(15 : 0) and C(16 : 1)omega5c; major hydroxy fatty acid, iso-C(17 : 0) 3-OH and major polyamine, homospermidine) supported the affiliation of both strains Gsoil 040(T) and Gsoil 052(T) to the genus Chitinophaga. The results of physiological and biochemical tests enabled the genotypic and phenotypic differentiation of the novel strains from the other recognized species of the genus Chitinophaga. Therefore, it is suggested that the new isolates represent two novel species, for which the names Chitinophaga ginsengisoli [corrected] sp. nov. [type strain Gsoil 040(T) (=KCTC 12654(T)=DSM 18108(T))] and Chitinophaga ginsengisoli sp. nov. [type strain Gsoil 052(T) (=KCTC 12592(T)=DSM 18017(T))] are proposed.