Aerobic Microbial Growth at Low Oxygen Concentrations

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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 × 10 −6 to 32 × 10 −6 m ), 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 × 10 −6 m . 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 O 2 concentration at low O 2 concentrations, and independent of O 2 concentration at high O 2 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 O 2 concentration at which the cells were grown, but the rate at low O 2 concentrations did not. There was evidence that, at low oxygen concentrations, oxygen diffusion through the cell substance limits respiration rate, at least in part.