A taxonomic study was carried out on a novel bacterial strain, designated MIC3010^T, which was isolated from a freshwater pond in Jeonju, Republic of Korea. Cells of the isolate were Gram-stain-negative, rod-shaped and non-motile. Comparison of the 16S rRNA gene sequences indicated that the isolate belonged to the family Flavobacteriaceae , with Flavobacterium haoranii LQY-7^T as its closest relative, with a similarity of 94.2 %. The predominant fatty acids of strain MIC3010^T were iso-C_15 : 1 G, iso-C_15 : 0 and iso-C_17 : 0 3-OH. The polar lipid profile of strain MIC3010^T revealed the presence of phosphatidylethanolamine (PE) and one unidentified lipid (L1) as major components. In addition, two aminolipids (AL1, AL2) and one glycolipid were present in small amounts. The DNA G+C content of the strain was 41.0 mol%. The strain contained MK-6 as the major quinone and sym-homospermidine as the predominant polyamine. On the basis of the evidence presented, it is concluded that strain MIC3010^T represents a novel species of the genus Flavobacterium , for which the name Flavobacterium fontis sp. nov. is proposed. The type strain is MIC3010^T ( = KACC 16593^T = JCM 18212^T).

Marine microbes, particularly Bacteroidetes, are a rich source of enzymes that can degrade diverse marine polysaccharides. Aquimarina sp. ERC-38, which belongs to the Bacteroidetes phylum, was isolated from seawater in South Korea. It showed agar-degrading activity and required an additional carbon source for growth on marine broth 2216. Here, the genome of the strain was sequenced to understand its agar degradation mechanism, and 3615 protein-coding sequences were predicted, which were assigned putative functions according to their annotated functional feature categories. In silico genome analysis revealed that the ERC-38 strain has several carrageenan-degrading enzymes but could not degrade carrageenan because it lacked genes encoding κ-carrageenanase and S1_19A type sulfatase. Moreover, the strain possesses multiple genes predicted to encode enzymes involved in agarose degradation, which are located in a polysaccharide utilization locus. Among the enzymes, Aq1840, which is closest to ZgAgaC within the glycoside hydrolase 16 family, was characterized using a recombinant enzyme expressed in Escherichia coli BL21 (DE3) cells. An enzyme assay revealed that recombinant Aq1840 mainly converts agarose to NA4. Moreover, recombinant Aq1840 could weakly hydrolyze A5 into A3 and NA2. These results showed that Aq1840 is involved in at least the initial agar degradation step prior to the metabolic pathway that uses agarose as a carbon source for growth of the strain. Thus, this enzyme can be applied to development and manufacturing industry for prebiotic and antioxidant food additive. Furthermore, our genome sequence analysis revealed that the strain is a potential resource for research on marine polysaccharide degradation mechanisms and carbon cycling.

The gastrointestinal microbiota are important for human health. Dietary intake may modulate the composition and metabolic function of the gut microbiome. We examined how the breakdown of prebiotic dietary fibers by the gut microbiome affects mucin secretion by intestinal epithelial cells. Metagenomic analyses of in vitro gut microbiome consortia revealed taxonomic profiles and genetic diversity of carbohydrate-active enzymes that digest polysaccharides. Two independent consortia exhibited different abilities to produce acetic acid, propionic acid, and butyric acid via the fermentation of polysaccharides derived from dietary fibers of grains and mushrooms. Although acetic acid generally had the highest concentration, the ratios of butyric acid and propionic acid to acetic acid varied depending on the polysaccharide source. These short-chain fatty acids affected morphological differentiation and mucin secretion in HT-29 human intestinal epithelial cells. These results suggest that prebiotic dietary fibers can be digested and metabolized by the gut microbiome to short-chain fatty acids, which can affect gut epithelial cells both directly and indirectly via the modulation of the gut microbiota and their enzymes.

Low-molecular-weight exopolysaccharides of Cordyceps militaris (LCMP), obtained by enzymatically digesting the exopolysaccharide produced by C. militaris, were purified and found to be comprised of 77.9% mannose and 22.1% glucose. Additionally, lactic acid bacteria (LAB) strains, including Enterococcus faecalis strain L4, Pediococcus acidilactici strain L25, and Companilactobacillus zhachilii strain L113, were isolated and their growth phenotypes and metabolites appeared in the presence or absence of purified LCMP were determined. In medium containing purified LCMP with low glucose, strains L4, L25, and L113 all exhibited auto-aggregation; however, co-aggregation occurred only with the strain L113. Moreover, culture media of strains L4, L25, and L113 in either the presence or the absence of LCMP could all inhibit the growth of pathogenic bacteria. Culture media of strains L4, L25, and L113 with purified LCMP contained higher concentrations of lactic acid and other organic acids than in media cultured without purified LCMP. Additionally, the proliferation of HT-29 cells was more effectively inhibited by culture media of strains L4, L25, and L113 with purified LCMP. Together, these results indicated that LCMP may provide positive effects for the host by promoting probiotics to inhibit the growth of pathogens and increase the production of metabolites related to anticancer activity.