Inhibition of anaerobic phosphate release by nitric oxide in activated sludge - PubMed (original) (raw)

Inhibition of anaerobic phosphate release by nitric oxide in activated sludge

E W Van Niel et al. Appl Environ Microbiol. 1998 Aug.

Abstract

Activated sludge not containing significant numbers of denitrifying, polyphosphate [poly(P)]-accumulating bacteria was grown in a fill-and-draw system and exposed to alternating anaerobic and aerobic periods. During the aerobic period, poly(P) accumulated up to 100 mg of P x g of (dry) weight. When portions of the sludge were incubated anaerobically in the presence of acetate, 80 to 90% of the intracellular poly(P) was degraded and released as orthophosphate. Degradation of poly(P) was mainly catalyzed by the concerted action of polyphosphate:AMP phosphotransferase and adenylate kinase, resulting in ATP formation. In the presence of 0.3 mM nitric oxide (NO) in the liquid-phase release of phosphate, uptake of acetate, formation of poly-beta-hydroxybutyrate, utilization of glycogen, and formation of ATP were severely inhibited or completely abolished. In cell extracts of the sludge, adenylate kinase activity was completely inhibited by 0.15 mM NO. The nature of this inhibition was probably noncompetitive, similar to that with hog adenylate kinase. Activated sludge polyphosphate glucokinase was also completely inhibited by 0.15 mM NO. It is concluded that the inhibitory effect of NO on acetate-mediated phosphate release by the sludge used in this study is due to the inhibition of adenylate kinase in the phosphate-releasing organisms. The inhibitory effect of nitrate and nitrite on phosphate release is probably due to their conversion to NO. The lack of any inhibitory effect of NO on adenylate kinase of the poly(P)-accumulating Acinetobacter johnsonii 210A suggests that this type of organism is not involved in the enhanced biological phosphate removal by the sludges used.

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Figures

FIG. 1

Phosphate release by F&D sludge under anaerobic conditions with acetate (▵), acetate plus 0.3 mM NO (○), NO alone, and in the absence of both acetate and NO (endogenous phosphate release) (□). DW, dry weight.

FIG. 2

Time course experiment with F&D sludge in the absence (▵) and presence (○) of 0.3 mM NO. (A) Uptake of acetate. (B) Formation of PHB. (C) Consumption of glycogen. DW, dry weight.

FIG. 3

Generation of ATP in F&D sludge under anaerobic conditions in the absence (□) and presence (▵) of 0.3 mM NO. The experiment was started by injecting acetate to a final concentration of 5 mM.

FIG. 4

Adenylate kinase activity as a function of the NO concentration in the liquid phase. ▵, adenylate kinase of F&D sludge; ○, hog adenylate kinase.

FIG. 5

Lineweaver-Burk plot of hog adenylate kinase at different inhibitor concentrations. □, 0.135 mM NO; ▵, 0.12 mM NO; ○, 0.05 mM NO; and ■, 0 mM NO.

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Inhibition of anaerobic phosphate release by nitric oxide in activated sludge - PubMed (original) (raw)