Mycolicibacterium aurantiacum sp. nov. and Mycolicibacterium xanthum sp. nov., two novel actinobacteria isolated from mangrove sediments

Two novel actinobacteria with the ability to degrade kerosene, designated as B3033 T and Y57 T , were isolated from mangrove sediments in Tieshan Harbour, South China Sea. Both strains are Gram-staining-positive, non-spore forming, slow-growing, oxidase-positive, non-motile and aerobic. Their major cellular fatty acids were C 16 : 0 and C 18 : 1 ω9 c . Analysis of 16S rRNA gene sequences revealed the close relationship of strain B3033 T to Mycobacterium kyogaense DSM 107316 T (99.4 % nucleotide identity) and strain Y57 T to Mycolicibacterium chubuense ATCC 27278 T (98.7 %) and Mycolicibacterium rufum JS14 T (98.7 %). Whole genome average nucleotide blast identity (ANI) and the digital DNA–DNA hybridization (dDDH) values between the two isolates and the type strains of species of the genus Mycolicibacterium were lower than 94 and 45 %, respectively, which were below the threshold values of 95 % (for ANI) and 70 % (for dDDH) recommended for bacterial species differentiation. The genome sequence of B3033 T comprised a circular 11.0 Mb chromosome with a DNA G+C content of 68.1 mol%. Y57 T had a genome size of 5.6 Mb and a DNA G+C content of 68.7 mol%. Genes involved in degradation of aromatic compounds and copper resistance were identified in the genomes of both strains that could improve their adaptive capacity to the mangrove environment. These results combined with those of chemotaxonomic analyses, MALDI-TOF MS profiles and phenotypic analyses support the affiliation of these strains to two novel species within the genus Mycolicibacterium , for which we propose the names Mycolicibacterium aurantiacum sp. nov. B3033 T (=KCTC 49712 T =MCCC 1K04526 T ) and Mycolicibacterium xanthum sp. nov. Y57 T (=KCTC 49711 T =MCCC 1K04875 T ) as type strains.