Kinetics of Sulfate and Acetate Uptake by Desulfobacter postgatei

Abstract

The kinetics of sulfate and acetate uptake was studied in the sulfate-reducing bacterium Desulfobacter postgatei (DSM 2034). Kinetic parameters (K(m) and V(max)) were estimated from substrate consumption curves by resting cell suspensions with [S]sulfate and [C]acetate. Both sulfate and acetate consumption followed Michaelis-Menten saturation kinetics. The half-saturation constant (K(m)) for acetate uptake was 70 muM with cells from either long-term sulfate- or long-term acetate-limited chemostat cultures. The average K(m) value for sulfate uptake by D. postgatei was about 200 muM. K(m) values for sulfate uptake did not differ significantly when determined with cells derived either from batch cultures or sulfate- or acetate-limited chemostat cultures. Acetate consumption was observed at acetate concentrations of </=1 muM, whereas sulfate uptake usually ceased at 5 to 20 muM. The results show that D. postgatei is not freely permeable to sulfate ions and further indicate that sulfate uptake is an energy-requiring process.