Loss of N2O reductase activity as an explanation for poor growth of Pseudomonas aeruginosa on N2O

Abstract

N20 uptake activity of cells and N20 reductase activity of the soluble fraction from denitrifying bacteria were assayed. Pseudomonas aeruginosa strains PAO1 and P1 lost most of their N20 uptake activity and the ability to grow well on N20 within 2 to 5 h after exposure to N20. Extensive loss of N20 reductase activity accompanied the nearly complete loss of N20 uptake activity under N20. Paracoccus denitrificans retained much, but not all, of both activities and the ability to grow vigorously on N20. The pattern with P. aeruginosa strain P2 resembled that for PAO1 and P1 except that loss of the activities proceeded at a slower rate and growth could continue for up to 12 h after exposure to N20. The inability of a number of P. aeruginosa strains to grow well on N20 is therefore a direct consequence of the nearly complete loss of N20 reductase activity. Turnover-dependent inactivation of N20 reductase and its reactivation under reducing conditions occurred in vitro for the enzyme from P. aeruginosa and Paracoccus denitrificans. These events may be significant in determining the activity level of N20 reductase in denitrifying bacteria during N20 respiration.

Long-term oxidant deficiency in Pseudomonas aeruginosa PAO303 results in cells which are non-culturable under aerobic conditions

“…2). The lack of significant growth with N20 was in good agreement with earlier observations [15,16], suggesting that N20 alone cannot support growth in P. aeruginosa. Arginine degradation under anaerobic conditions has previously been shown to be sufficient for maintenance of cell motility and growth in P. aerugmosa under nutrient-rich conditions [6].…”

Loss of Nitrous Oxide Reductase in Pseudomonas aeruginosa Cultured under N 2 O as Determined by Rocket Immunoelectrophoresis

“…When the nitrous oxide reductase cellular content decreased in the presence of N20 to 25 to 50% of the value observed during growth on nitrate, growth on N20 became slow, with doubling times of 1 day or more. This kind of response is reminiscent of the nonlinear relationship observed previously between the growth of P. aeruginosa strains on N20 and N20 uptake activity (7). Why growth should virtually cease when N20 respiration can and does continue at significant rates is unknown, but this phenomenon may be related in part to basal energy requirements for maintenance of cellular integrity without growth.…”

“…Pseudomonas aeruginosa is unusual among denitrifiers in that it grows poorly on N20 alone but can grow efficiently on the N20 produced as a metabolic intermediate during the reduction of nitrate or nitrite to N2 (1-3). Previous studies in our laboratory have determined that the immediate cause for poor growth on N20 is a progressive loss of nitrous oxide uptake and reductase activities in cells grown under N20 (7). In this study, we determined by using rocket immunoelectrophoresis (4) that the progressive loss of enzyme activity corresponds to a progressive decrease in the intracellular concentration of nitrous oxide reductase.…”

Nitrate Removal from Ground Water: A Review

“…When electrons are transferred from the donor to the acceptor, the organism gains energy which was applied for the synthesis of a new cell mass and the maintenance of the existing cellmass. The enzymes associated with denitrification are synthesized under anaerobic or partially aerobic conditions 41 . Nitrate reduction to nitrogen gas occurred as:…”