Effect of temperature stress on structure and function of the methanogenic archaeal community in a rice field soil

The effect of a brief (24 h) temperature shift to 4degreesC (low-temperature stress) or 50degreesC (high-temperature stress) was studied in methanogenic slurries of Italian rice field soil incubated at either constant 30degreesc or 15degreesC. Low-temperature (low-T) stress showed no effect in either the 30degreesC or the 15degreesC incubations. High-temperature (high-T) stress. on the other hand, generally resulted in an increase in the partial pressure of H-2, and the concentrations of acetate and propionate, which accumulated to about 100-200 Pa, 4-6 mM and 0.7-0.9 mM, respectively. The increase in H2 was transient for 8-15 days. The increases in acetate and propionate were transient for about 20 days only in the 30degreesC incubations, but persisted in the 15degreesC incubations until the end of the experiment, The high-T stress did not result in inhibition of CH., production in the 30degreesC incubations, but transiently inhibited the 15degreesC incubations for about 25-30 days. The archaeal community in the soils was analyzed by terminal restriction fragment length polymorphism of the gene of the SSU rRNA. In the 15degreesC incubations, the relative gene frequency of members of the Methanosarcinaceae decreased over an incubation period of 54 days, while those of Methanosaetaceae and of methanogenic rice cluster I increased, Temperature stress, high-T stress in particular, tended to reverse this trend. In the 30degreesC incubations. on the other hand, the relative gene frequency of archaeal members showed the opposite temporal trend or remained constant unlike the 15degreesC incubations. Again, high-T stress tended to reverse these trends, but the observed effects were much smaller in the 30degreesC incubations than in the 15degreesC incubations. In conclusion, a brief high-T stress affected structure and function of the methanogenic archaeal community of rice field soil. (C) 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.