BACTERIAL-DEGRADATION OF M-NITROBENZOIC ACID

Pseudomonas sp. strain JS51 grows on m-nitrobenzoate (m-NBA) with stoi chiometric release of nitrite, m-NBA-grown cells oxidized m-NBA and pr otocatechuate but not 3-hydroxybenzoate, 4-hydroxy-3-nitrobenzoate, 4- nitrocatechol, and 1,2,4-benzenetriol. Protocatechuate accumulated tra nsiently when succinate-grown cells were transferred to media containi ng m-NBA. Respirometric experiments indicated that the conversion of m -NBA to protocatechuate required 1 mol of oxygen per mol of substrate. Conversions conducted in the presence of O-18(2) showed the incorpora tion of both atoms of molecular oxygen into protocatechuate. Extracts of m-NBA-grown cells cleaved protocatechuate to 2-hydroxy-4-carboxymuc onic semialdehyde. These results provide rigorous proof that m-NBA is initially oxidized by a dioxygenase to produce protocatechuate which i s further degraded by a 4,5-dioxygenase.