Discovery of a New Rosamicin Derivative from Endophytic Micromonospora rosaria FoRo54 Using Genome Mining Technology

Endophytic FoRo54 was isolated from the roots of <i>Oryza rufipogon</i> (Dongxiang wild rice) collected in China. Based on morphological characteristics and phylogenetic analysis of the 16S rRNA gene sequence, strain FoRo54 was identified as closely related to <i>Micromonospora rosaria</i>. The complete genome of FoRo54 consists of a linear chromosome of 7,057,852 bp with a GC content of 73.8 mol%. Genome mining using antiSMASH revealed 27 biosynthetic gene clusters (BGCs) potentially involved in secondary metabolite biosynthesis, including those associated with kanamycin, rosamicin, and asukamycin, consistent with the antibacterial activities of the strain. Application of a combined genome mining strategy enabled further exploration of the strain's metabolic potential. One new rosamicin derivative, <i>N</i>-demethyl rosamicin (<b>1</b>), together with three known compounds, rosamicin (<b>2</b>), SCH 23831 (<b>3</b>), and tylactone (<b>4</b>), were isolated from fermentation broth. Antibacterial evaluation revealed that compounds <b>1</b>-<b>4</b> exhibited potent inhibitory activity against <i>Staphylococcus aureus</i>. Furthermore, based on genomic analysis, the biosynthetic pathway and putative gene functions responsible for these metabolites were proposed. Collectively, these findings highlight the metabolic versatility of the endophytic <i>Micromonospora rosaria</i> FoRo54, underscoring its potential as a valuable source of novel bioactive metabolites and providing a genomic framework for future heterologous expression and functional genetic characterization.