Kinetics of Sulfate and Acetate Uptake by Desulfobacter postgatei

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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 [ 35 S]sulfate and [ 14 C]acetate. Both sulfate and acetate consumption followed Michaelis-Menten saturation kinetics. The half-saturation constant ( K m ) for acetate uptake was 70 μM 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 μM. 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 μM, whereas sulfate uptake usually ceased at 5 to 20 μM. The results show that D. postgatei is not freely permeable to sulfate ions and further indicate that sulfate uptake is an energy-requiring process.

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