THE PRODUCTION OF ANTIBIOTICS IN SOIL V. BREAKDOWN OF GRISEOFULVIN IN SOIL

When griseofulvin (I; R = Cl, R' = OCH3), a chlorine-containing antibiotic produced by Penicillium nigricans, was added to fresh garden loam, after an initial lag it disappeared rapidly. When further griseofulvin was added it was inactivated from the start and at rates which increased with each successive addition, suggesting that it was degraded biologically. The numbers of one organism, a Pseudomonas sp., increased in the soil steadily after adding griseofulvin. When a little soil was added to a solution (pH 7.0) containing inorganic salts and griseofulvin as the sole carbon source, bioassays showed that the griseofulvin disappeared within 5 days. An organism isolated from the broth was identified as the Pseudomonas sp. thought to break down griseofulvin in soil. Griseofulvin also disappeared from a broth at pH 5.0 inoculated with soil, but at this lower pH value a dematiaceous fungus was responsible for its breakdown. The Pseudomonas sp. also degraded two derivatives of griseofulvin, dechloro-griseofulvin (I; R = H, R' = OCH3) and the amine (I; R = Cl, R' = NH2). Cl- was detected in the solutions after breakdown of griseofulvin by the Pseudomonas; the amount present agreed well with that calculated on the assumption that all the chlorine in the griseofulvin supplied was liberated as Cl-. Spectrophotometric examination of the solutions showed no metabolites with the aromatic ring intact, and confirmed the complete breakdown of griseofulvin suggested by the liberation of Cl-.