Investigation of an endophytic Streptomyces sp. from the liverwort Bazzania trilobata: A new source for abyssomicins

Abstract

Liverworts are the most ancient group of land plants and share intimate symbioses with microorganisms, yet their endophytes have remained unexplored as a source of unique compounds. As part of an ongoing search for novel and bioactive compounds from microbial associates of liverworts, an endophytic Streptomyces sp. LH003 cultured from Bazzania trilobata was identified as a new source for abyssomicins. Three compounds, namely abyssomicin 2 (1), abyssomicin 4 (2), and neoabyssomicin B (3) were isolated from the crude ethyl acetate extract of the endophytic Streptomyces sp. fermentation culture using sem-preparative HPLC. The chemical structures of the compounds were established using 1D and 2D NMR, HRESIMS, UV, ECD, and by comparison to published data. This work represents the first study of an endophyte obtained from the liverwort B. trilobata, and the first report of isolated metabolites from a liverwort-associated endophytic bacterium. The discovery of abyssomicins from this unique microbial source broadens the known ecological and taxonomic distribution of these compounds. The production of known antibacterial metabolites by an endophytic bacterium may have implications for microbial interactions within the liverwort. Additionally, this study discusses the distribution pattern of known abyssomicins across different bacterial genera, highlighting the distinct biosynthetic origins of these compounds.