Kineochelins - a novel group of siderophores from an Antarctic bacterium
BackgroundThe global rise of antimicrobial resistance has intensified the search for new microbial metabolites from underexplored environments and taxonomic groups. Extreme and geographically isolated habitats, such as Antarctic terrestrial ecosystems, represent promising reservoirs of novel biosynthetic diversity, particularly among rare and difficult-to-cultivate actinomycetes, where chemical mediators are thought to play key roles in microbial persistence and interaction under resource-limited conditions. ResultsHere, we report the characterization of kineochelins, a previously undescribed group of siderophores produced by an Antarctic isolate, Actinokineospora sp. UV203 representing difficult to cultivate actinomycetes. Structural elucidation revealed a set of closely related congener molecules with a mixed-ligand architecture consistent with metal-chelating activity. Genome mining combined with transcriptomic analysis identified the involvement of a dedicated nonribosomal peptide synthetase-encoding biosynthetic gene cluster responsible for kineochelin production. Comparative genomic analyses showed that, although kineochelin biosynthetic genes share limited homology with those of known mixed-ligand siderophores, their biosynthetic pathways differ substantially in gene content and organization, indicating a distinct evolutionary lineage. Functional characterization of kineochelins demonstrated strong and selective iron chelation, with pronounced affinity for ferric and ferrous iron. Crude culture extracts inhibited the growth of bacterial strains isolated from the same Antarctic environment, suggesting that kineochelin-associated chemistry contributes to iron-mediated competitive interactions within native microbial communities. In addition, kineochelin-enriched fractions exhibited selective inhibitory activity against the opportunistic yeast pathogen Nakaseomyces glabratus and a clinical isolate of Saccharomyces cerevisiae associated with invasive infection. ConclusionsTogether, these findings expand the known chemical and biosynthetic diversity of the genus Actinokineospora and demonstrate that Antarctic rare actinomycetes are a valuable source of novel natural products with potential relevance for microbial ecology and biotechnology. The ecological activities of kineochelins highlight the role of iron acquisition in shaping microbial interactions in extreme environments and underscore the biotechnological potential of metabolites derived from underexplored polar microorganisms.