Nocardioides proteolyticus sp. nov. and Nocardioides ureilyticus sp. nov., isolated from desert rhizosphere soils

Strains SYSU DS0651^T and SYSU DS0663^T were isolated from the rhizosphere soils of <i>Tamarix chinensis</i> Lour. and <i>Alhagi camelorum</i> Fisch., respectively, in the Turpan-Hami Basin, Xinjiang, China. Both strains were Gram-stain-positive, oxidase-negative, catalase-positive, non-motile and rod-shaped. They were capable of growing at 4-45 ℃ and at pH 7.0-8.0. Notably, strain SYSU DS0651^T exhibited the ability to hydrolyse both casein and gelatin, while SYSU DS0663^T demonstrated urease activity. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains SYSU DS0651^T and SYSU DS0663^T belong to the genus <i>Nocardioides,</i> showing the highest sequence similarities to <i>Nocardioides vastitatis</i> 21Sc5-5^T (98.13%) and <i>Nocardioides oceani</i> SOB77^T (98.13%), respectively. The genome sizes of strains SYSU DS0651^T and SYSU DS0663^T were 3,919,402 and 3,985,477 bp, respectively, with DNA G+C contents of 72.7% and 73.0 %. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the two strains and their closest relatives were below the species-delineation thresholds (ANI: 95-96%; dDDH: 70%). A polyphasic taxonomic analysis revealed that strains SYSU DS0651^T and SYSU DS0663^T represent two novel species within the genus <i>Nocardioides</i>. Therefore, the names <i>Nocardioides proteolyticus</i> sp. nov. (type strain SYSU DS0651^T=MCCC 1K09396^T=KCTC 59499^T) and <i>Nocardioides ureilyticus</i> sp. nov. (type strain SYSU DS0663^T=MCCC 1K09407^T=KCTC 59500^T) are proposed.