Mycobacterium jinjuensis sp. nov., a Novel Acid-Fast Bacterium Isolated from a Pneumonia Patient

A novel Gram-stain-positive, acid-fast, aerobic, slow-growing bacterium, designated strain ND9-15 ^T was isolated from the sputum of a patient with pneumonia in a tertiary hospital in Jinju, Gyeongsangnam-do, Republic of Korea. The strain exhibited growth at temperatures ranging from 15 to 37 °C, with optimal growth at 25-30 °C. It grew at pH values of 5.0-9.0, with an optimum pH of 7.0-7.5, and in the presence of 0-4% (w/v) NaCl, optimally at 0.5-1%. Based on the 16S rRNA gene sequencing, strain ND9-15 ^T clustered within the genus Mycobacterium, showing the closest relationship to Mycobacterium wolinskyi DSM 44493 ^T (98.7% sequence similarity), Mycobacterium mageritense DSM 44476 ^T (98.5%), and Mycobacterium palauense DSM 44914 ^T (98.3%). However, whole-genome-based analyses revealed that the strain is more closely related to M. celeriflavum, M. komaniense, M. novocastrense, and M. malmesburyense, with average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values well below the species delineation thresholds (ANI < 85%, dDDH < 30%). The complete genome of strain ND9-15 ^T comprises a circular chromosome of 5.1 Mb with a DNA G + C content of 66.9% and 4,650 predicted coding sequences. Chemotaxonomic analysis identified C₁₆:₀, C₁₈:₀ 10-methyl (TBSA), and summed feature 7 (C₁₉:₁ ω7c/C₁₉:₁ ω6c/C₁₉:₀ cyclo ω10c) as major fatty acids. The predominant polar lipids were phosphatidylethanolamine, phosphatidylinositol, and diphosphatidylglycerol. Biochemically, strain ND9-15 ^T was differentiated from its closest relatives by its protease activity, and lack of nitrate reduction and urease activity. Based on its phenotypic, chemotaxonomic, and phylogenetic characteristics, strain ND9-15 ^T is proposed as the type strain of a novel species, Mycobacterium jinjuensis sp. nov.