BIODEGRADATION OF 3-CHLOROBENZOATE AND FORMATION OF BLACK COLOR IN THE PRESENCE AND ABSENCE OF BENZOATE

Four isolates of Pseudomonas from soil and sewage utilized 3-chlorobenzoate (3-CBA) adaptively as sole source of carbon and energy. Two of these were studied in detail. Their doubling times in batch culture were about twice as long on chlorobenzoate as on benzoate or glucose. Both isolates showed oxygen uptake on catechol, without lag, when grown on either benzoate or 3-CBA. One strain, designated Pseudomonas H1, could oxidize a key intermediate, 4-chlorocatechol, only when grown on 3-CBA. Pseudomonas H2 could oxidize the chlorocatechol not only when grown on 3-CBA but also when grown on benzoate. Benzoate-adapted P. H1 therefore accumulated chlorocatechols when incubated with a mixture of 3-CBA and benzoate, whereas P. H2 under the same conditions did not. The accumulated chlorocatechols inhibited further oxygen uptake, and in alkaline media they polymerized to a black, melanin-like pigment. Intense black pigment, similar to that formed by P. I, was formed if raw sewage was incubated with a mixture of 3-CBA and benzoate. The pigment was not formed if the sewage was first adapted by incubation with 3-CBA. © 1979 Springer-Verlag.