Competition between oxygen and nitrate respirations in continuous culture of Pseudomonas aeruginosa performing aerobic denitrification

Abstract

Continuous culture of P. aeruginosa was conducted with nitrate-containing media under the dilution rates (D) of 0.026, 0.06, and 0.13/h and the dissolved oxygen concentrations (DO) of 0-2.2 mg/L. The bacterium performed simultaneous O(2) and nitrate respiration in all of the systems studied. For each D, the (apparent) cell yield from glucose (Y(X/S)) was lower at zero DO, but did not change substantially with non-zero DO. In non-zero DO systems, Y(X/S) increased with increasing D, and when fit with a model considering cell death, gave the following parameters: maximum cell yield Y(X/S) (m) = 0.49, maintenance coefficient M(S) = 0.029 (/h), and cell decay constant k(d) = 0.014/h. The same model failed to describe the behaviors of zero-DO systems, where neither glucose nor nitrate was limiting and the limiting factor(s) remained unknown. The cell yield from accepted electron (Y(X/e)) was however relatively constant in all systems, and the energy yield per electron accepted via denitrification was estimated at approximately 69% of that via O(2) respiration. A closer examination revealed that increasing DO enhanced O(2) respiration only at extremely low DO ( <0.05 mg/L), beyond which the increasing DO only slightly increased its weak inhibition on denitrification. While O(2) was the preferred electron acceptor, the fraction of electrons accepted via denitrification increased with increasing D.

Fosfomycin and Tobramycin in Combination Downregulate Nitrate Reductase Genes narG and narH , Resulting in Increased Activity against Pseudomonas aeruginosa under Anaerobic Conditions

“…aeruginosa uses nitrate as an alternative terminal electron acceptor during anaerobic respiration and can also perform aerobic denitrification (28)(29)(30)(31). In the present study, a significant difference in the expression of the majority of nitrate reductase genes under anaerobic as opposed to aerobic conditions was not found.…”

Involvement of Nitric Oxide in Biofilm Dispersal of Pseudomonas aeruginosa

“…Therefore, it is not clear how ONOO Ϫ is produced inside microcolonies, which are thought to be largely anaerobic (15). However, it is also clear that O 2 gradients can occur inside microcolonies, and simultaneous O 2 and NO 3 Ϫ respiration has recently been demonstrated for P. aeruginosa populations (8). Thus, it is feasible that ONOO Ϫ could be produced inside microcolonies.…”

Development of a Novel Biofilm Continuous Culture Method for Simultaneous Assessment of Architecture and Gaseous Metabolite Production

“…In order to assess the utility of the AFGAS method, we utilized Pseudomonas aeruginosa as a model organism. P. aeruginosa is a gram-negative ubiquitous bacterium that is well-established as a model for biofilm formation (5,27) and also possesses a functional denitrification pathway (3,9,29). Denitrification is an anaerobic respiration process that utilizes N oxides instead of oxygen as terminal electron acceptors in the respiratory chain (31).…”

“…In this study, conversion efficiency was defined as follows: E ϭ {[2(P 1 ϩ P 2 )]/S} ϫ 100, where E is the conversion efficiency (a percentage), S is the total consumed NO 3 Ϫ (in micromoles), P 1 is the total N 2 (in micromoles) accumulated in the headspace, and P 2 is the total N 2 O (in micromoles) accumulated in the headspace. For biofilm experiments, the integral of the NO 3 Ϫ concentration curve was assumed to be total consumed NO 3 Ϫ . Dissolved oxygen concentration measurement.…”