B. Baumann et al., INHIBITION OF DENITRIFICATION ACTIVITY BUT NOT OF MESSENGER-RNA INDUCTION IN PARACOCCUS-DENITRIFICANS BY NITRITE AT A SUBOPTIMAL PH, Antonie van Leeuwenhoek, 72(3), 1997, pp. 183-189
The influence of pH on the denitrification activity of a continuous cu
lture of Paracoccus denitrificans was studied in relation to the prese
nce of nitrite. After a transition from aerobic to anaerobic condition
s at the suboptimal pH of 6.8, P. denitrificans was not able to build
up a functional denitrification pathway. Nitrite accumulated in the me
dium as the predominant denitrification product. Although the nitrite
reductase gene was induced properly, the enzyme could not be detected
at sufficient amounts in the culture. These observations indicate that
either translation was somehow inhibited, or once synthesized nitrite
reductase was inactivated, possibly by the high concentrations of nit
rous acid (HNO2). Interestingly, when a P. denitrificans culture which
was grown to steady-state under anaerobic conditions was then exposed
to suboptimal pHs, cells exhibited a reduced overall denitrification
activity, but neither nitrite nor any other denitrification intermedia
te accumulated.