KINETICS OF NITROBACTER-AGILIS AT EXTREME SUBSTRATE, PRODUCT AND SALT CONCENTRATIONS

Measurement and description of the effects of extreme conditions on biological nitrite oxidation was the aim of this study, using Nitrobacter agilis (ATCC 14123) as a model nitrifying bacterium. The initial O-2 consumption rate of a concentrated cell suspension was used as a rapid assay to measure the effects. Several relationships, based on Michaelis-Menten kinetics, were derived. These relationships describe the behaviour of N. agilis with respect to substrate inhibition, product inhibition and various salt concentrations up to 500 mmol.dm(-3) with the pH ranging from 6.5 to 8.5. Substrate and product inhibition were pH-dependent and the substrate inhibition could be related to the undissociated nitrite. In contrast with previous reports on nitrite-oxidizing microorganisms, we did not observe severe inhibition by NH4+.