The GenBank accession number for the 16S rRNA gene sequence of strain K13M18 T is MK285603. The NCBI accession number for the wholegenome sequence of strain K13M18 T is CP034328. †These authors contributed equally to this work Four supplementary figures and two supplementary tables are available with the online version of this article.

Nontuberculous mycobacterial pulmonary diseases (NTM-PDs) are emerging as global health threats with issues of antibiotic resistance. Accumulating evidence suggests that the gut–lung axis may provide novel candidates for host-directed therapeutics against various infectious diseases. However, little is known about the gut–lung axis in the context of host protective immunity to identify new therapeutics for NTM-PDs. This study was performed to identify gut microbes and metabolites capable of conferring pulmonary immunity to NTM-PDs. Using metabolomics analysis of sera from NTM-PD patients and mouse models, we showed that the levels of l -arginine were decreased in sera from NTM-PD patients and NTM-infected mice. Oral administration of l -arginine significantly enhanced pulmonary antimicrobial activities with the expansion of IFN-γ-producing effector T cells and a shift to microbicidal (M1) macrophages in the lungs of NTM-PD model mice. Mice that received fecal microbiota transplants from l -arginine-treated mice showed increased protective host defense in the lungs against NTM-PD, whereas l -arginine-induced pulmonary host defense was attenuated in mice treated with antibiotics. Using 16S rRNA sequencing, we further showed that l -arginine administration resulted in enrichment of the gut microbiota composition with Bifidobacterium species. Notably, oral treatment with either Bifidobacterium pseudolongum or inosine enhanced antimicrobial pulmonary immune defense against NTM infection, even with multidrug-resistant clinical NTM strains. Our findings indicate that l -arginine-induced gut microbiota remodeling with enrichment of B. pseudolongum boosts pulmonary immune defense against NTM infection by driving the protective gut–lung axis in vivo .

A novel coccus-shaped, Gram-stain-positive, non-motile and aerobic bacterium, designated strain NSG39, was isolated from the intestine of a Korean rockfish, Sebastes schlegelii. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the newly isolated strain NSG39 was closely related to Tessaracoccus flavus RP1 (98.0 %). The isolate grew at 15-37 °C, pH 7-9 and 0-4 % (w/v) salinity, with optimal growth at 30 °C, pH 8 and 0 % (w/v) salinity. The cell wall of the organism contained ll-diaminopimelic acid as a diagnostic diamino acid, and ribose, mannose, glucose and galactose as diagnostic sugars. The polar lipid comprised diphosphatidylglycerol, phosphatidylglycerol, three glycolipids and four unidentified polar lipids. The major cellular fatty acid was anteiso-C15 : 0 (47.2 %). The major menaquinone was MK-9 (H4). The DNA G+C content of the isolate was 68.8 mol%. The genome-based orthologous average nucleotide identity value for strain NSG39 and T. flavus RP1 was 76.6 %. Based on the phylogenetic analysis and its biological characteristics, strain NSG39 is considered to represent a novel species of the genus Tessaracoccus, for which the name Tessaracoccus aquimaris is proposed. The type strain is NSG39 (=KACC 17540=JCM 19289).

A novel coccus-shaped, Gram-stain-positive, non-motile and facultative aerobic bacterium, designated strain D7T301T, was isolated from the small intestine of a marten, Martes flavigula, which was killed on the road in Pocheon-si, Gyeonggi-do, Republic of Korea. Grown on a tryptic soy yeast agar plate, colonies had a creamy colour and irregular form. The new isolate formed a monophyletic clade with Vagococcus penaei CD276T on a phylogenetic consensus tree based on the 16S rRNA gene sequence. The isolate grew optimally at 37 °C and pH 7 in the presence of 0.5 % (w/v) NaCl. The isolate was catalase- and oxidase-negative. The cell-wall peptidoglycan was type A4α l-Lys-d-Asp. The major cellular fatty acids were C16 : 0, C14 : 0, and C16 : 1ω9c. The predominant respiratory quinone was menaquinone MK-7 (85.1 %). The DNA G+C content based on genome sequencing was 33.8 mol%. The average nucleotide identity value obtained from comparative genomic analysis between strain D7T301T and V. penaei CIP 109914T was 72.6 %. On the basis of the phenotypic, phylogenetic, biochemical, chemotaxonomic, and genotypic analyses, Vagococcusmartis is proposed as a novel species of the genus Vagococcus. The type strain is D7T301T (=KCTC 21069T=JCM 31178T).

A strictly anaerobic, Gram-stain-positive, non-motile and coccoid- or oval-shaped bacterium, designated strain KB1, was isolated from a faecal sample of a patient with diverticulitis in South Korea. Degeneracies in the 16S rRNA gene sequence of strain KB1 were resolved by cloning, which yielded five different sequences with heterogeneity. Phylogenetic analysis based on the 16S rRNA gene sequences showed that strain KB1 formed a monophyletic branch with species in the genus Blautia, with highest sequence similarity to the type strain of Blautia producta (97.7-98.9 %), followed by Blautia coccoides (97.5-98.1 %). Strain KB1 was able to grow at temperatures of between 15 and 42 °C, with optimal growth at 37 °C, and in the presence of 20 % dehydrated bile. Acetic acid, succinic acid, lactic acid and fumaric acid were produced by strain KB1 from Gifu anaerobic medium broth as metabolic fermentation end-products. The major cellular fatty acids of strain KB1 were C14 : 0, C16 : 0 and C16 : 0 dimethyl aldehyde. The DNA G+C content was 46.3 mol%. The average nucleotide identity value between strain KB1 and the type strain of B. producta was 84.1 %. On the basis of polyphasic analysis, strain KB1 represents a novel species in the genus Blautia, for which the name Blautia hominis sp. nov. is proposed. The type strain is KB1 (=KCTC 15618=JCM 32276).