Khatmiamycin, a motility inhibitor and zoosporicide against the grapevine downy mildew pathogen Plasmopara viticola from Streptomyces sp. ANK313

In the course of our screening for anti-peronosporomycetal agents, we isolated a new compound khatmiamycin (1), together with five known metabolites, GTRI-02 (3), 4-ethyl-5-methyl-heptanamide (4), aloesaponarin II (5), LL-C10037α (6) and LL-C10037β (7) from the culture broth of a terrestrial Streptomyces sp. ANK313. The structures of these metabolites were assigned on the basis of their spectroscopic data. Khatmiamycin (1) exhibited potent motility inhibitory (100%) and lytic (83±7%) activities against zoospores of the grapevine downy mildew pathogen Plasmopara viticola at 10 μg ml−1, followed by compounds 5 (MIC 25 μg ml−1), 7, 6, 3 in the order of decreasing activity. Khatmiamycin (1) also showed potent antibacterial activity against Staphylococcus aureus and Streptomyces viridochromogenes (Tü57) by causing inhibition zones of 11 and 14 mm diameter, respectively, at the dose of 40 μg per disk. This is the first report on motility inhibitory and lytic activities of metabolites from a terrestrial Streptomyces species against the zoospores of downy mildew pathogen P. viticola.