Description of sp. nov., an endophytic actinobacterium producing naphthomycin A and its genome insight for discovering bioactive compounds.

Endophytic actinobacteria are a group of bacteria living inside plant tissue without harmful effects, and benefit the host plant. Many can inhibit plant pathogens and promote plant growth. This study aimed to identify a strain of as a novel species and study its antibiotics production. An endophytic actinobacterium, strain TML10 was isolated from a surface-sterilized leaf of a Thai medicinal plant ( Craib and Hutch). As a result of a polyphasic taxonomy study, strain TML10 was identified as a member of the genus . Strain TML10 was an aerobic actinobacterium with well-developed substrate mycelia with loop spore chains and spiny surface. Chemotaxonomic data, including cell wall components, major menaquinones, and major fatty acids, confirmed the affiliation of strain TML10 to the genus . The results of the phylogenetic analysis, including physiological and biochemical studies in combination with a genome comparison study, allowed the genotypic and phenotypic differentiation of strain TML10 and the closest related type strains. The digital DNA-DNA hybridization (dDDH), Average nucleotide identity Blast (ANIb), and ANIMummer (ANIm) values between strain TML10 and the closest type strain, CH5-8 were 38.8%, 88.5%, and 90.8%, respectively. The name proposed for the new species is sp. nov. (TML10 = TBRC 15050 = NRRL B-65638). Strain TML10 was further studied for liquid and solid-state fermentation of antibiotic production. Solid-state fermentation with cooked rice provided the best conditions for antibiotic production against methicillin-resistant . The elucidation of the chemical structures from this strain revealed a known antimicrobial agent, naphthomycin A. Mining the genome data of strain TML10 suggested its potential as a producer of antbiotics and other valuable compounds such as ε-Poly-L-lysine (ε-PL) and arginine deiminase. Strain TML10 contains the A gene encoding arginine deiminase and could degrade arginine .