Microbacterium wangyouchuni sp. nov. and Microbacterium zouquanmingi sp. nov., isolated from soil in Mongolian marmot (Marmota sibirica) burrows.

Abstract

Four Gram-stain-positive, aerobic, non-motile and rod-shaped bacterial strains, designated A82T, A588, A196T and A204, were isolated from soil samples collected from Marmota sibirica burrows in Hulun Buir, Nei Mongol Autonomous Region, China. All four strains grew at 4-30 °C, pH 6.0-10.0 and 0-6.5% (wt/v) NaCl, and they were positive for oxidase and catalase activities. Phylogenetic analysis of 16S rRNA gene sequences indicated that the four strains belonged to two species within the genus Microbacterium. Strains A82T and A588 exhibited the highest sequence similarity to Microbacterium profundi Shh49T (98.83%) and Microbacterium murale 1 Gi-001T (98.67%). Strains A196T and A204 were most closely related to Microbacterium aerolatum NBRC 103071T (99.10%) and Microbacterium shaanxiense CCNWSP60T (98.63%). Comparing the four isolates with their reference strains showed that average nucleotide identity and digital DNA-DNA hybridization values were below the accepted species-delineation benchmarks of 95-96 and 70%, respectively. For the type strains A82T and A196T, the DNA G+C content was 64.7 and 65.4 mol%, respectively. Chemotaxonomic analysis revealed that both type strains possessed MK-13 as the sole respiratory quinone. Additionally, diphosphatidylglycerol, phosphatidylglycerol and unidentified glycolipids were the major polar lipids. Furthermore, anteiso-C15 : 0 was identified as the major fatty acid, and the diamino acid in the cell-wall peptidoglycan contained alanine, glutamic acid, glycine, aspartic acid and ornithine. Therefore, strains A82T/A588 and A196T/A204 represent two novel species within the genus Microbacterium. Microbacterium wangyouchuni sp. nov. (A82T/A588, type strain A82T=GDMCC 1.5865T=JCM 38342T) and Microbacterium zouquanmingi sp. nov. (A196T/A204, type strain A196T=GDMCC 1.6024T=JCM 38357T) are proposed.