Whole-genome analysis and fermentation-metabolite profiling of a cellulolytic Arthrobacter sp. FMD isolated from forest musk-deer faeces.

Most studies on the intestinal microbiota of the forest musk deer (Moschus berezovskii) are based on community-level sequencing, and functional characterisation of individual strains is rare. Here we isolated strain FMD from deer faeces by selecting on CMC-Na as the sole carbon source; it utilises xylose, trehalose and fructose and is positive for urease and the methyl-red test. Whole-genome sequencing yielded a 4.05 Mb chromosome (GC 64.1%, four contigs, 3 726 CDS), and phylogenomic analyses (20 core genes, ANI and SNP tree) placed the isolate in the genus Arthrobacter; the strain was designated Arthrobacter sp. FMD. The genome encodes abundant catabolic functions, including 128 CAZymes, 27 COG and 34 KEGG genes for carbohydrate metabolism, and 54 COG and 45 KEGG genes for amino-acid metabolism, while VFDB and PHI searches indicate low pathogenic potential. Fermentation of wheat bran with Arthrobacter sp. FMD increased carboxylic acids from 21.8% to 33.4% and decreased fatty acyls from 24.2% to 10.8%. Isoquercitrin, 2-oxindole-3-acetic acid and 5-hydroxyindole-3-acetic acid were the most up-regulated metabolites, whereas Leu-Trp, 6′-O-feruloyl catalpol and Cnidioside A were the most down-regulated. Isoleucylvaline, γ-glutamyl-methionine and N²-acetylornithine showed the highest increases among amino-acid derivatives, and isovaleric, valeric, 2-hydroxy-2-methylbutyric and 2-hydroxy-3-methylbutyric acids were the predominant organic-acid products. These findings suggest that Arthrobacter sp. FMD deploys a coordinated set of hydrolases and downstream catabolic enzymes that degrade lignocellulose-derived substrates, reduce anti-nutritional factors and enrich organic acids, nucleosides and flavonoids, highlighting its potential to improve feed utilisation and gut health in the forest musk deer.