KINETICS OF NITROBACTER-AGILIS AT EXTREME SUBSTRATE, PRODUCT AND SALTCONCENTRATIONS

Measurement and description of the effects of extreme conditions on bi ological nitrite oxidation was the aim of this study, using Nitrobacte r agilis (ATCC 14123) as a model nitrifying bacterium. The initial O-2 consumption rate of a concentrated cell suspension was used as a rapi d assay to measure the effects. Several relationships, based on Michae lis-Menten kinetics, were derived. These relationships describe the be haviour of N. agilis with respect to substrate inhibition, product inh ibition 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 undisso ciated nitrite. In contrast with previous reports on nitrite-oxidizing microorganisms, we did not observe severe inhibition by NH4+.