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- LLBT, was isolated from cow dung collected from Shangzhi, Heilongjiang Province, PR China. Cells of strain NEAU-LLBT were Gram-stain-positive, non-motile, aerobic and non-spore-forming. Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain NEAU-LLBT belonged to the genus Microbacte-rium. Strain NEAU-LLBT had high 16S rRNA sequence similarities of 98.81 and 98.41 % to Microbacterium paludicola DSM 16915(T) and Microbacterium marinilacus DSM 18904T, and less than 98 % to other members of the genus Microbacterium. Chemotaxonomic charac-teristics 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-LLBT was 70.2 mol%. In addition, the average nucleotide identity values between strain NEAU-LLBT 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-LLBT is considered to represent a novel species of the genus Microbacterium, for which the name Microbacterium stercoris sp. nov is proposed, with NEAU-LLBT (=CCTCCAA 2018028(T)=JCM 32660(T)) as the type strain.