A volatile inhibitor of spore germination from Streptomyces griseoruber (Ryabova & Preobrazhenskaya)

Abstract

Two methods for the extraction and identification of a volatile fungistatic inhibitor from cultures of Streptomyces griseoruber (Ryabova & Preobrazhenskaya) are described. A headspace vapour sampling method using adsorption of volatiles by a porous polymer proved unsatisfactory, and was replaced by a simultaneous distillation-extraction method. A bioassay procedure was developed to test the resulting extract for inhibition of spore germination of a test organism, Cladosporium cladosporioides (Fres.) de Vries. The same procedure was adapted to assay fractions of the crude extract collected directly from a preparative G.C. outlet. Two fractions were found to be active. The components of each were identified by mass spectrometry using a 'probe trapping' method. This involves trapping material eluting from the G.C. on a short column of Poropak Q, which is introduced to the mass spectrometer by means of a conventional solids probe. The active compound in the first fraction was methyl vinyl ketone (MVK). Activity was confirmed by performing assays on C. cladosporioides using authentic samples of MVK. The inhibitor in the second fraction has not as yet been determined.