BE-31405

While isolating fungal strains from soil samples, two strains, Talaromyces siamensis FKA-61 and Phomopsis sp. FKA-62, were found to produce a black pigment near the boundary with an adjoining colony on agar plates. Moreover, strain FKA-61 inhibited the growth of strain FKA-62. Co-culture of T. siamensis FKA-61 with Phomopsis sp. FKA-62 resulted in the production of an antifungal agent, BE-31405, which proved active against Phomopsis sp. FKA-62. We screened for fungal genera that have the ability to induce production of antifungal BE-31405. Surprisingly, production of BE-31405 was induced only by co-culturing T. siamensis FKA-61 with a variety of BE-31405-sensitive fungal strains but never with BE-31405-insensitive strains. This is the first report of the induced production of a specific antibiotic active against antibiotic-sensitive fungal strains by co-culturing with them.

A new antifungal antibiotic, BE-31405, was isolated from the culture broth of a fungal strain, Penicillium minioluteum F31405. BE-31405 was isolated by adsorption on high porous polymer resin (Diaion HP-20), followed by solvent extraction, precipitation and crystallization. BE-31405 showed potent growth inhibitory activity against pathogenic fungal strains such as Candida albicans, Candida glabrata and Cryptococcus neoformans, but did not show cytotoxic activity against mammalian cells such as P388 mouse leukemia. The mechanism studies indicated that BE-31405 inhibited the protein synthesis of C. albicans but not of mammalian cells.