Byung Hee Chun

Effects of Temperature on Bacterial Communities and Metabolites during Fermentation of Myeolchi-Aekjeot, a Traditional Korean Fermented Anchovy Sauce.

Myeolchi-aekjeot (MA) in Korea is produced outdoors without temperature controls, which is a major obstacle to produce commercial MA products with uniform quality. To investigate the effects of temperature on MA fermentation, pH, bacterial abundance and community, and metabolites were monitored during fermentation at 15°C, 20°C, 25°C, and 30°C. Initial pH values were approximately 6.0, and pH values increased after approximately 42 days, with faster increases at higher temperatures. Bacterial abundances increased rapidly in all MA samples after quick initial decreases during early fermentation and then they again steadily decreased after reaching their maxima, which were significantly greater at higher temperatures. Bacterial community analysis revealed that Proteobacteria and Tenericutes were predominant in all initial MA samples, but they were rapidly displaced by Firmicutes as fermentation progressed. Photobacterium and Mycoplasma belonging to Proteobacteria and Tenericutes, respectively, which may include potentially pathogenic strains, were dominant in initial MA, but decreased with the growth of Chromohalobacter, which occurred faster at higher temperatures––they were dominant until 273 and 100 days at 15°C and 20°C, respectively, but not detected after 30 days at 25°C and 30°C. Chromohalobacter also decreased with the appearance of subsequent genera belonging to Firmicutes in all MA samples. Tetragenococcus, halophilic lactic acid bacteria, appeared predominantly at 20°C, 25°C, and 30°C; they were most abundant at 30°C, but not detected at 15°C. Alkalibacillus and Lentibacillus appeared as dominant genera with the decrease of Tetragenococcus at 25°C and 30°C, but only Lentibacillus was dominant at 15°C and 20°C. Metabolite analysis showed that amino acids related to tastes were major metabolites and their concentrations were relatively higher at high temperatures. This study suggests that high temperatures (approximately 30°C) may be appropriate in MA fermentation, in the light of faster disappearance of potentially pathogenic genera, higher amino acids, growth of Tetragenococcus, and faster fermentation.

Chromohalobacter is a Causing Agent for the Production of Organic Acids and Putrescine during Fermentation of Ganjang, a Korean Traditional Soy Sauce.

Ganjang, a Korean traditional fermented soy sauce, is prepared by soaking doenjang-meju (fermented soybeans) in approximately 20% (w/v) solar salt solution. The metabolites and bacterial communities during ganjang fermentation were simultaneously investigated to gain a better understanding of the roles of the microbial population. The bacterial community analysis based on denaturing gradient gel electrophoresis of 16S rRNA gene sequences showed that initially, the genus Cobetia was predominant (0 to 10 d), followed by Bacillus (5 to 74 d), and eventually, Chromohalobacter became predominant until the end of the fermentation process (74 to 374 d). Metabolite analysis using (1)H-NMR showed that carbon compounds, such as fructose, galactose, glucose, and glycerol, probably released from doenjang-meju, increased rapidly during the early fermentation period (0 to 42 d). After removal of doenjang-meju from the ganjang solution (42 d), the initial carbon compounds remained nearly constant without the increase of fermentation products. At this point, Bacillus species, which probably originated from doenjang-meju, were predominant, suggesting that Bacillus is not mainly responsible for ganjang fermentation. Fermentation products including acetate, lactate, α-aminobutyrate, γ-aminobutyrate, and putrescine increased quickly with the rapid decrease of the initial carbon compounds, while Chromohalobacter, probably derived from the solar salts, was predominant. Multivariate redundancy analysis indicated that the Chromohalobacter population was closely correlated with the production of the organic acids and putrescine during the ganjang fermentation. These results may suggest that Chromohalobacter is a causing agent responsible for the production of organic acids and putrescine during ganjang fermentation and that the solar salts, not doenjang-meju, is an important microbial source for ganjang fermentation.

Large-scale examination of functional and sequence diversity of 2-oxoglutarate/Fe(II)-dependent oxygenases in Metazoa

BACKGROUND The 2-oxoglutarate/Fe(II)-dependent oxygenase (2OG oxygenase) superfamily in Metazoa is responsible for protein modification, nucleic acid repair and/or modification, and fatty acid metabolism. METHODS Phylogenetic analysis, protein sequence similarity network (SSN) and other bioinformatics tools were used to analyze the evolutionary relationship and make functional inferences of Metazoa 2OG oxygenases. RESULTS Sixty-four 2OG oxygenases have been previously found in Homo sapiens; they catalyze two reactions: hydroxylation and demethylation. Phylogenetic analyses indicated that enzymes with similar domain architecture are always clustered together, and the redox function can be performed by the 2OG oxygenase domain or Jumonji C (JmjC) domain, where the JmjC domain is always fused to other functional domains. We used the SSN to make functional inferences and to conduct distribution analysis of Metazoa 2OG oxygenases. >11,000 putative 2OG oxygenases across Metazoa could be assigned potential functions based on the SSN. The multiple sequence alignments showed that the residues binding iron are most highly conserved in both the 2OG oxygenase domain and JmjC domain. In contrast, the residues binding oxoglutarate are quite different in the two domains: the 2OG oxygenase domain tends to have an Arg/Lys at the C terminus, whereas the JmjC domain, an Asn/Lys residue in the middle region. CONCLUSIONS The results indicated that gene duplication and vertical gene transfer have played important roles in 2OG oxygenase evolution in Metazoa and clarified the difference between the 2OG oxygenase domain and JmjC domain. GENERAL SIGNIFICANCE These findings expand the understanding of the diversity, evolution, and functions of 2OG oxygenases.

Pan-genomic and transcriptomic analyses of Leuconostoc mesenteroides provide insights into its genomic and metabolic features and roles in kimchi fermentation

The genomic and metabolic features of Leuconostoc (Leu) mesenteroides were investigated through pan-genomic and transcriptomic analyses. Relatedness analysis of 17 Leu. mesenteroides strains available in GenBank based on 16S rRNA gene sequence, average nucleotide identity, in silico DNA-DNA hybridization, molecular phenotype, and core-genome indicated that Leu. mesenteroides has been separated into different phylogenetic lineages. Pan-genome of Leu. mesenteroides strains, consisting of 999 genes in core-genome, 1,432 genes in accessory-genome, and 754 genes in unique genome, and their COG and KEGG analyses showed that Leu. mesenteroides harbors strain-specifically diverse metabolisms, probably representing high evolutionary genome changes. The reconstruction of fermentative metabolic pathways for Leu. mesenteroides strains showed that Leu. mesenteroides produces various metabolites such as lactate, ethanol, acetate, CO2, mannitol, diacetyl, acetoin, and 2,3-butanediol through an obligate heterolactic fermentation from various carbohydrates. Fermentative metabolic features of Leu. mesenteroides during kimchi fermentation were investigated through transcriptional analyses for the KEGG pathways and reconstructed metabolic pathways of Leu. mesenteroides using kimchi metatranscriptomic data. This was the first study to investigate the genomic and metabolic features of Leu. mesenteroides through pan-genomic and metatranscriptomic analyses, and may provide insights into its genomic and metabolic features and a better understanding of kimchi fermentations by Leu. mesenteroides.

A proposal of Leuconostoc mesenteroides subsp. jonggajibkimchii subsp. nov. and reclassification of Leuconostoc mesenteroides subsp. suionicum (Gu et al., 2012) as Leuconostoc suionicum sp. nov. based on complete genome sequences

The type strains of four subspecies of Leuconostocmesenteroides, L. mesenteroidessubsp. mesenteroides, L. mesenteroidessubsp. cremoris, L. mesenteroidessubsp. dextranicum and L. mesenteroidessubsp. suionicum, and strain DRC1506T, used as a starter culture for commercial kimchi production in Korea, were phylogenetically analyzed on the basis of their complete genome sequences. Although the type strains of the four L. mesenteroides subspecies and strain DRC1506T shared very high 16S rRNA gene sequence similarities (>99.72 %), the results of analysis of average nucleotide identity (ANI), in silico DNA-DNA hybridization (DDH) and core-genome-based relatedness indicated that they could form five different phylogenetic lineages. The type strains of L. mesenteroidessubsp. mesenteroides, L. mesenteroidessubsp. cremoris and L. mesenteroidessubsp. dextranicum and DRC1506T shared higher ANI and in silico DDH values than the thresholds (95-96 % and 70 %, respectively) generally accepted for different species delineation, whereas the type strain of L. mesenteroidessubsp. suionicum (DSM 20241T) shared lower ANI (<94.1 %) and in silico DDH values (<57.0 %) with the other four L. mesenteroides lineage strains, indicating that DSM 20241T couldn be reclassified as representing a different species. Here, we report that DRC1506T represents a novel subspecies within the species Leuconostoc mesenteroides, for which the name Leuconostoc mesenteroidessubsp. jonggajibkimchii subsp. nov. is proposed. The type strain is DRC1506T (=KCCM 43249T=JCM 31787T). In addition, L. mesenteroidessubsp. suionicum is also reclassified as Leuconostoc suionicum. sp. nov. (type strain DSM 20241T=ATCC 9135T=LMG 8159T=NCIMB 6992T).

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).

Complete Genome Sequences of Two Acetic Acid-Producing Acetobacter pasteurianus Strains (Subsp. ascendens LMG 1590T and Subsp. paradoxus LMG 1591T)

Citation: Jia B, Chun BH, Cho GY, Kim KH, Moon JY, Yeo S-H and Jeon CO (2017) Complete Genome Sequences of Two Acetic AcidProducing Acetobacter pasteurianus Strains (Subsp. ascendens LMG 1590 and Subsp. paradoxus LMG 1591T). Front. Bioeng. Biotechnol. 5:33. doi: 10.3389/fbioe.2017.00033 Complete Genome Sequences of two acetic acid-producing Acetobacter pasteurianus Strains (Subsp. ascendens LMG 1590t and Subsp. paradoxus LMG 1591t)

Complete genome sequence of Bacillus methylotrophicus JJ-D34 isolated from deonjang, a Korean traditional fermented soybean paste.

Bacillus methylotrophicus JJ-D34 showing good proteolytic and antipathogenic activities was isolated from doenjang, a Korean traditional fermented soybean paste. Here, we report the complete genome sequence of strain JJ-D34 harboring a 4,105,955 bp circular chromosome encoding 4044 genes with a 46.24% G+C content, which will provide insights into the genomic basis of its effects and facilitating its application to doenjang fermentation.

Distinct Histone Modifications Modulate DEFB1 Expression in Human Vaginal Keratinocytes in Response to Lactobacillus spp.

Vaginal commensal lactobacilli are considered to contribute significantly to the control of vaginal microbiota by competing with other microflora for adherence to the vaginal epithelium and by producing antimicrobial compounds. However, the molecular mechanisms of symbiotic prokaryotic-eukaryotic communication in the vaginal ecosystem remain poorly understood. Here, we showed that both DNA methylation and histone modifications were associated with expression of the DEFB1 gene, which encodes the antimicrobial peptide human β-defensin-1, in vaginal keratinocyte VK2/E6E7 cells. We investigated whether exposure to Lactobacillus gasseri and Lactobacillus reuteri would trigger the epigenetic modulation of DEFB1 expression in VK2/E6E7 cells in a bacterial species-dependent manner. While enhanced expression of DEFB1 was observed when VK2/E6E7 cells were exposed to L. gasseri, treatment with L. reuteri resulted in reduced DEFB1 expression. Moreover, L. gasseri stimulated the recruitment of active histone marks and, in contrast, L. reuteri led to the decrease of active histone marks at the DEFB1 promoter. It was remarkable that distinct histone modifications within the same promoter region of DEFB1 were mediated by L. gasseri and L. reuteri. Therefore, our study suggested that one of the underlying mechanisms of DEFB1 expression in the vaginal ecosystem might be associated with the epigenetic crosstalk between individual Lactobacillus spp. and vaginal keratinocytes.

Pontibacterium granulatum gen. nov., sp. nov., isolated from a tidal flat

A Gram-stain-negative, strictly aerobic, moderately halophilic bacterium, designated A-1T, was isolated from a tidal flat of the Taean coast in South Korea. Cells were motile rods with a single flagellum showing oxidase-negative and catalase-positive activities and contained poly-β-hydroxyalkanoic acid granules. Growth of strain A-1T was observed at 20-40 °C (optimum, 30 °C), pH 6.0-10.5 (optimum, pH 7.0) and in the presence of 1.0-6.0 % (w/v) NaCl (optimum, 2.0 %). Strain A-1T contained C16 : 0, summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c) and summed feature 8 (comprising C18 : 1ω7c and/or C18 : 1ω6c) as the major fatty acids. The major polar lipids of strain A-1T were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The isoprenoid quinones detected were ubiquinone-7 and ubiquinone-8. The G+C content of the genomic DNA was 51.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain A-1T formed a distinct phylogenetic lineage from other genera within the family Oceanospirillaceae. Strain A-1T shared low 16S rRNA gene sequence similarities with other taxa (≤94.9 %). On the basis of phenotypic, chemotaxonomic and molecular properties, it is clear that strain A-1T represents a novel genus and species of the family Oceanospirillaceae, for which the name Pontibacterium granulatum gen. nov., sp. nov. is proposed. The type strain is A-1T (=KACC 18119T=JCM 30136T).