Antimicrobial potential of culturable actinobacteria isolated from the Pacific oyster Crassostrea gigas (Bivalvia, Ostreidae)

Aims: Explore the diversity of culturable actinobacteria isolated from the Pacific oyster Crassostrea gigas with special emphasis on their antimicrobial activity Methods and Results: For the characterization of the isolated actinobacteria, a polyphasic approach was adopted and thereby phenotypic descriptions, phyloge netic analysis, evaluations of antimicrobial activities and chemical analyses of crude extracts through HPLC and LC- HRESIMS were performed. Five strains were iso lated from C. gigas. The 16S rRNA gene analysis revealed that three of them were taxonomically affiliated to the genus Streptomyces and the other two strains were related to Micromonospora. High inhibition was detected against different test mi croorganisms such as Candida albicans, Staphylococcus aureus, Bacillus subtilis and Mycobacterium smegmatis. On the basis of the chemical analysis, 11 compounds from the active fractions of the crude extracts were determined, and 8 were related putatively to previously reported compounds. Conclusions: Actinobacteria isolated from C. gigas represent an interesting reser voir of antimicrobial compounds, and further study to uncover the full capacity of this source is encouraged. Significance and Impact: At present, the study of actinobacteria and their antimi crobial potential from uncommon sources as C. gigas is vital to the development of new therapeutic agents to cope with the widespread resistance of human pathogens.