INITIAL REACTIONS IN THE ANAEROBIC OXIDATION OF TOLUENE AND M-XYLENE BY DENITRIFYING BACTERIA

Pseudomonas sp. strain T and Pseudomonas sp. strain K172 grow with tol uene under denitrifying conditions. We demonstrated that anaerobic deg radation of toluene was initiated by direct oxidation of the methyl gr oup. Benzaldehyde and benzoate accumulated sequentially after toluene was added when cell suspensions were incubated at 5 degrees C. Strain T also grows anaerobically with m-xylene, and we demonstrated that deg radation was initiated by oxidation of one methyl group. In cell suspe nsions incubated at 5 degrees C 3-methylbenzaldehyde and 3-methylbenzo ate accumulated after m-xylene was added. Toluene- or m-xylene-grown s train T cells were induced to the same extent for oxidation of both hy drocarbons. In addition, the methyl group-oxidizing enzyme system of s train T also catalyzed the oxidation of each isomer of the chloro- and fluorotoluenes to the corresponding halogenated benzoate derivatives. In contrast, strain K172 only oxidized 4-fluorotoluene to 4-fluoroben zoate, probably because of the narrow substrate specificity of the met hyl group-oxidizing enzymatic system. During anaerobic growth with tol uene strains T and K172 produced two transformation products, benzylsu ccinate and benzylfumarate. About 0.5% of the toluene carbon was conve rted to these products.