New Metabolites From the Co-culture of Marine-Derived Actinomycete Streptomyces rochei MB037 and Fungus Rhinocladiella similis 35

Co-culture of different microbes simulating the natural state of microbial community may produce potentially new compounds because of nutrition or space competition. To mine its metabolic potential in depth, co-culture of MB037 with a gorgonian-derived fungus 35 was carried out to stimulate the production of new metabolites in this study, using pure cultivation as control. Five metabolites were isolated successfully from co-culture broth, including two new fatty acids with rare nitrile group, borrelidins J and K ( and ), one chromone derivative as a new natural product, 7-methoxy-2,3-dimethylchromone-4-one ( ), together with two known 18-membered macrolides, borrelidin ( ) and borrelidin F ( ). The structures of - were elucidated by using a combination of NMR and MS spectroscopy, ester hydrolysis, and optical rotation methods. Interestingly, and were obtained only in co-culture. Though was gained from either co-culture or single culture, its production was increased significantly by co-culture. Compound exhibited significant antibacterial activity against methicillin-resistant with a MIC value of 0.195 μg/mL.