Microbacterium candidum sp. nov. and Microbacterium capsulatum sp. nov., isolated from waste landfill.

Abstract

Two Gram-stain-positive, oxidase-negative, non-motile and rod-shaped strains (ASV49^T and ASV81^T) were isolated from a waste landfill in Shanghai, China. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the two strains are associated with members of the genus Microbacterium. Strains ASV49^T and ASV81^T were most closely related to Microbacterium rhizosphaerae JCM 31396^T and Microbacterium bovistercoris CCTCC AA 2018025^T with 98.5 and 98.0% 16S rRNA gene sequence similarities, respectively. The genomic DNA G+C contents of strains ASV49^T and ASV81^T were 69.5 and 70.5 mol %, respectively. Strains ASV49^T and ASV81^T exhibited the highest average nucleotide identity values of 81.7 and 85.3% against their closest relatives Microbacterium xylanilyticum JCM 13591^T and M. rhizosphaerae JCM 31396^T, respectively. Corresponding digital DNA-DNA hybridization values were 25.1 and 30.9%, respectively. Strains ASV49^T and ASV81^T grew optimally at pH 7.0 and 28 °C on Reasoner's 2A. Strain ASV81^T produced capsules, but ASV49^T did not. Both isolates shared the following chemotaxonomic characteristics in common: the major fatty acids of anteiso-C_15 : 0, iso-C_16 : 0 and anteiso-C_17 : 0; the respiratory quinones of MK-11, MK-12, MK-13 and MK-10; the polar lipids of diphosphatidylglycerol and phosphatidylglycerol; and the cell wall amino acids of ornithine, alanine, glycine and glutamic acid. Based on the genomic, phenotypic and chemical characteristics, strains ASV49^T and ASV81^T represent two novel species of the genus Microbacterium, for which the names Microbacterium candidum sp. nov. and Microbacterium capsulatum sp. nov. are proposed. The type strains are ASV49^T (=GDMCC 1.4109^T=JCM 36480^T) and ASV81^T (=GDMCC 1.4110^T=JCM 36481^T), respectively.