Microbacterium stercoris sp. nov., an indole acetic acid-producing actinobacterium isolated from cow dung

A novel growth-promoting and indole acetic acid-producing strain, designated NEAU-LLB^T, was isolated from cow dung collected from Shangzhi, Heilongjiang Province, PR China. Cells of strain NEAU-LLB^T were Gram-stain-positive, non-motile, aerobic and non-spore-forming. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain NEAU-LLB^T belonged to the genus Microbacterium. Strain NEAU-LLB^T had high 16S rRNA sequence similarities of 98.81 and 98.41 % to Microbacterium paludicola DSM 16915^T and Microbacterium marinilacus DSM 18904^T, and less than 98 % to other members of the genus Microbacterium. Chemotaxonomic characteristics showed that MK-11 and MK-12 were detected as the predominant menaquinones. The peptidoglycan contained glutamic acid, aspartic acid, glycine, ornithine and a small amount of alanine, with ornithine as the diagnostic diamino acid. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and an unidentified glycolipid. The major fatty acids were identified as anteiso-C_15 : 0, iso-C_16 : 0 and iso-C_17 : 0. The genomic DNA G+C content of strain NEAU-LLB^T was 70.2 mol%. In addition, the average nucleotide identity values between strain NEAU-LLB^T and its reference strains, M. paludicola DSM 16915^T, M. marinilacus DSM 18904^T and M. album SYSU D8007^T, were found to be 81.1, 79.4 and 78.7 %, respectively, and the level of digital DNA-DNA hybridization between them were 23.8, 22.6 and 21.8 %, respectively. Based on the phenotypic, phylogenetic and genotypic data, strain NEAU-LLB^T is considered to represent a novel species of the genus Microbacterium, for which the name Microbacterium stercoris sp. nov is proposed, with NEAU-LLB^T (=CCTCC AA 2018028^T=JCM 32660^T) as the type strain.