Description of two novel Marinobacter species isolated from saline-alkali soil: Marinobacter alkalisoli sp. nov. and Marinobacter shunpengi sp. nov.

Four Gram-staining negative, non-motile, rod-shape bacteria, named strains GN3S48T, HN1S83, LN3S78T, and M1N3S26, were isolated from the bulk saline soils, in Baotou, China. Among them, strains GN3S48T and HN1S83 could degrade 100 mg l-1n-hexadecane as sole carbon and energy source for their growth. Phylogenetic analyses showed that the four strains always formed two distinct clades: Strain LN3S78T clustered with strain M1N3S26, and strain GN3S48T clustered with strain HN1S83. Nonetheless, all four strains tightly clustered and shared the highest 16S rRNA gene similarities with Marinobacter species. Specifically, clade of strains LN3S78T and M1N3S26 cluster with Marinobacter lipolyticus CGMCC 1.7282T, while clade of strains GN3S48T and HN1S83 clustered with Marinobacter zhanjiangensis CCTCC AB 208029T. The ANIb and AAI values between strains GN3S48T and HN1S83 were 96.4% and 94.6%, respectively, while those between strains LN3S78T and M1N3S26 were 99.3% and 99.1%, respectively. All ANI and AAI values between the four strains and their closest relatives were below the 95.0% species delineation threshold. The predominant respiratory quinone of the four strains was Q-9. Based on this polyphasic result, the two clades should be identified as two novel species within the genus Marinobacter. Thus, Marinobacter alkalisoli sp. nov. (type strain GN3S48T = CGMCC 1.62232T = KCTC 8701T = JCM 37359 T) and Marinobacter shunpengi sp. nov. (type strain LN3S78T = CGMCC 1.62233T = KCTC 8702T = JCM 37360T) are proposed. The metagenomic analysis revealed that the two new species are globally distributed in high-salt habitats. In addition, comparative genomic analysis confirmed that alkane-degrading genes are ubiquitous in Marinobacter strains.