THE NITRITE REDUCTASE GENE OF PSEUDOMONAS-AERUGINOSA - EFFECT OF GROWTH-CONDITIONS ON THE EXPRESSION AND CONSTRUCTION OF A MUTANT BY GENE DISRUPTION

The expression of nitrite reductase has been tested in a wild-type str ain of Pseudomonas aeruginosa (Pao1) as a function of nitrate concentr ation under anaerobic and aerobic conditions. Very low levels of basal expression are shown under non-denitrifying conditions (i.e. absence of nitrate, in both aerobic and anaerobic conditions); anaerobiosis is not required for high levels of enzyme production in the presence of nitrate. A Pseudomonas aeruginosa strain, mutated in the nitrite reduc tase gene, has been obtained by gene replacement. This mutant, the fir st of this species described up to now, is unable to grow under anaero bic conditions in the presence of nitrate. The anaerobic growth can be restored by complementation with the wild-type gene.