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.