The affinity of Methanosarcina barkeri 227 for acetate and hydrogen at different incubation temperatures was investigated. Increasing the temperature from 20 to 37 degrees C resulted in a 4.5-fold increase in K(m) for acetate and a 4.8-fold increase for hydrogen. The corresponding increase in V(max) for acetate was 8.3-fold (5.4-fold for hydrogen). This response implied a decrease in the temperature coefficient (Q(10)) and hence a decrease in the temperature dependency as a function of decreasing substrate concentration.