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Aerobic Microbial Growth at Low Oxygen Concentrations

Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706

ABSTRACT

Sterilizable membrane probes were used to study the relation between oxygen concentration and respiration rate in Candida utilis growing on acetate. When the organism was grown in a continuous fermentor at various dissolved oxygen concentrations (0.23 x 10^–6 to 32 x 10^–6M), with time allowed for full adaptation to each oxygen concentration, the relationship between oxygen concentration and growth rate simulated Michaelis-Menten behavior, giving an apparent K_m for oxygen of 1.3 x 10^–6M. When respiration rate was measured at various oxygen concentrations without allowing time for adaptation, it was found that the respiration rate was directly proportional to O₂ concentration at low O₂ concentrations, and independent of O₂ concentration at high O₂ concentrations. Transition from one type of behavior to the other was fairly abrupt. The respiration rate in the presence of excess oxygen depended on the O₂ concentration at which the cells were grown, but the rate at low O₂ concentrations did not. There was evidence that, at low oxygen concentrations, oxygen diffusion through the cell substance limits respiration rate, at least in part.

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