Novel microbiota sp. nov. has a protective effect against inflammatory bowel disease.

A novel Gram-negative, obligate anaerobe, non-motile, flagella-lacking, catalase- and oxidase-negative, coccobacilli-shaped bacterial strain designated AGMB02718 was isolated from swine feces. The 16S rRNA gene analysis indicated that strain AGMB02718 belonged to the genus with the highest similarity to 4NBBH2 (= DSM 106860) (sequence similarity of 96.2%), forming a distinct phylogenetic lineage. Its growth occurred at 25-45°C (optimal 37°C) and in 0.5-1% NaCl (optimal 0.5%). Strain AGMB02718 was asaccharolytic and contained menaquinone 6 (MK-6) and methylmenaquinone 6 (MMK-6) as the predominant respiratory quinones. The major cellular fatty acids in the isolate were C9 and C. Based on the whole-genome sequencing analysis, strain AGMB02718 had a 2,606,253 bp circular chromosome with a G + C content of 62.2%. The average nucleotide identity value between strain AGMB02718 and 4NBBH2 was 72.1%, while the digital DNA-DNA hybridization value was 20.9%. Interestingly, genome analysis suggested that strain AGMB02718 possessed a low-toxicity lipopolysaccharide (LPS) because the genome of the isolate does not include and genes for Kdo-Lipid A (KLA) assembly, which confers high toxicity to LPS. Moreover, macrophage stimulation assay confirmed that AGMB02718 produced LPS with low toxicity. Because the low-toxicity LPS produced by the family is involved in regulating host immunity and low-toxicity LPS-producing strains can help maintain host immune homeostasis, we evaluated the anti-inflammatory activity of strain AGMB02718 against inflammatory bowel disease (IBD). As a result, strain AGMB02718 was able to prevent the inflammatory response in a dextran sulfate sodium (DSS)-induced colitis model. Therefore, this strain represents a novel species of that has a protective effect against DSS-induced colitis, and the proposed name is sp. nov. The type strain is AGMB02718 (=GDMCC 1.2717 = KCTC 25541).