A NOVEL PATHWAY FOR THE CATABOLISM OF 4-NITROTOLUENE BY PSEUDOMONAS

Eleven strains of Pseudomonas were isolated by selective enrichment on 4-nitrotoluene (4NT). They all utilized 4NT, 4-nitrobenzyl alcohol (4 NBA) or 4-nitrobenzoate (4NBZate) as sole sources of carbon and nitrog en. One strain, TW3, was used for more detailed studies. 4NT-grown cel ls of TW3 take up O2 when incubated in the presence of 4NBA, 4-nitrobe nzaldehyde (4NBZ) and 4NBZate. HPLC analysis of culture supernatants s howed that 4NBZ and 4NBZate were formed when 4NT-grown cells were incu bated with 4NBA, whereas only 4NBZate was found when they were incubat ed with 4NBZ. Two dehydrogenases were detected in extracts of 4NT-grow n cells. 4NBA dehydrogenase could be assayed by a dye-linked assay whe reas 4NBZ dehydrogenase activity was linked to NAD+ reduction. No nitr ite was detected in supernatants of 4NBZate-grown cells incubated with 4NBZate but the nitrogen appeared as ammonium. The only aromatic ring -cleavage dioxygenase that was induced during growth on the nitroaroma tics was protocatechuate 3,4-dioxygenase. It is proposed that the path way for 4NT catabolism proceeds via 4NBA, 4NBZ and 4NBZate and ultimat ely to protocatechuate with release of the nitro group as ammonium.