Microbacterium jiangjiandongii sp. nov. and Microbacterium wangruii sp. nov., two β-cryptoxanthin-producing bacteria isolated from intestinal contents of Marmota himalayana

Abstract

Four Gram-stain-positive, facultative anaerobic, yellow-pigmented and short rod-shaped strains, designated zg-Y625^T, zg-Y843, zg-Y1090^T and zg-Y1211, were isolated from the intestinal contents of Marmota himalayana in Qinghai Province, PR China. Strains zg-Y625^T and zg-Y1090^T showed the highest 16S rRNA gene sequence similarities of 99.7% and 99.9% to Microbacterium pullorum DSM 112390^T, respectively, followed by 99.2% and 99.5% to Microbacterium oleivorans JCM 14341^T and 99.1% and 99.0% to Microbacterium paulum LMG 32277^T. Phylogenetic analyses based on 16S rRNA gene sequences and phylogenomic analyses using whole-genome sequences revealed that these four strains belong to the genus Microbacterium, forming two separate clades distinct from all other known Microbacterium species. The genome sizes of strains zg-Y625^T and zg-Y1090^T were 3.26 and 3.07 Mb, respectively, with DNA G+C contents of 70.5 and 70.9 mol%. The average nucleotide identity and digital DNA-DNA hybridization values between each of the novel strains and the available members of the genus Microbacterium were all below the species thresholds. Both type strains contained diphosphatidylglycerol and phosphatidylglycerol as predominant polar lipids with one unidentified glycolipid for zg-Y625^T and two unidentified glycolipids for zg-Y1090^T. The predominant respiratory quinone in zg-Y625^T was MK-13, whilst in zg-Y1090^T, both MK-11 and MK-13 were identified as the major quinones. The major fatty acids (>10%) in strains zg-Y625^T and zg-Y843 were anteiso-C_{15 : 0}, anteiso-C_{17 : 0} and iso-C_{16 : 0}, whereas for zg-Y1090^T and zg-Y1211, the predominant fatty acids were anteiso-C_{15 : 0} and anteiso-C_{17 : 0}. Based on phenotypic, phylogenetic, genomic and chemotaxonomic data, two novel species in the genus Microbacterium are proposed, namely, Microbacterium jiangjiandongii sp. nov. (zg-Y625^T=GDMCC 1.3931^T=JCM 36203^T) and Microbacterium wangruii sp. nov. (zg-Y1090^T=GDMCC 1.3930^T=JCM 36205^T).

Keywords: Marmota himalayana; Microbacterium; novel species; phylogenetic analysis.