The antimicrobial activities of twenty-twosubstances structurally related to staurosporine, aglycone in the indolocarbazole and bis-indole series were examined against Streptomyces chartreusis and Streptomyces griseus, Bacillus cereus, Escherichia coli, Candida albicans and Botrytis cinerea. Inhibition of sporulation was examined also on the two species of Streptomyces. Unlike literature reports for efficient protein kinase inhibitors, staurosporine and K-252a, no evident correlation could be found either between protein kinase inhibitory potencies and inhibition of sporulation of the Streptomyces species, or protein kinase inhibitory potencies and growth of all microorganisms tested.A weak activity against C. albicans was observed for the chloro-indolocarbazole compounds as already reported for structurally related substances from the cyanobacterium Tolypothrix tjipanasensis.Streptomycetes are Gram-positive bacteria which form a spore-producing aerial mycelium. It was found recently that the microbial indolocarbazole metabolites, staurosporine1) and K-252a2) (Fig. 1), inhibit aerial mycelium formation and antibiotic production by Streptomyces griseus3\ These compounds are knownalso as inhibitors of eukaryotic protein kinase C.To determine if there was a general link between activity on protein kinase C and inhibition of spore formation, the in vitro growth inhibitory effect of twenty-two compounds in the indolocarbazole andbis-indole series were tested against S. griseus and Streptomyces chartreusis. The activities of these twenty-two compoundstowards protein kinase C and protein kinase A have been determined previously; some of them were active, others not4~7). Production of the secondary metabolite calcimycin (A 23187) by S. chartreusis was examined when the culture was incubated with an efficient protein kinase C inhibitor and with a compound inactive towards this enzyme. The antimicrobial activities against Bacillus cereus, Escherichia coli, Candida albicans and Botrytis cinerea were determined also.

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