Anaerobically denitrifying Pseudomonas stutzeri may transiently accumulate from O% to 100% of nitrate as nitrite, depending on the nitrate availability during the preceding 24 h. The variations of transient nitrite level were related to the length of previous nitrate starvation. Cells harvested in a late anaerobic growth phase did not accumulate any nitrite during denitrification. Five hours of nitrate starvation caused about 40% (mol/mol) nitrite formation from the further added nitrate and 16 h nearly 80%, Concomitant with this, whereas the nitrate reduction capacity was not significantly affected, the initial nitrite reduction capacity was decreased. These results suggested that nitrate starvation caused a rapid loss of the originally produced nitrite-reducing capacity in the preculture. The lost capacity could be regenerated when nitrate or nitrite was resupplied to the cells, To investigate the nature of the restoration of nitrite-reducing capacity, chloramphenicol was used. The presence of chloramphenicol at 83 mu g/ml entirely stopped this restoration, which was otherwise observed in all instances, This indicated that the recovery of nitrite-reducing activity required de novo protein synthesis, which was further confirmed by Western immunoblot assay of cd(1) nitrite reductase.