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 4 degrees C (low-temperature stress) or 50 degrees C (high-temperature stress) was studied in methanogenic slurries of Italian rice field soil incubated at either constant 30 degrees C or 15 degrees C. Low-temperature (low-T) stress showed no effect in either the 30 degrees C or the 15 degrees C 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 H(2) was transient for 8-15 days. The increases in acetate and propionate were transient for about 20 days only in the 30 degrees C incubations, but persisted in the 15 degrees C incubations until the end of the experiment. The high-T stress did not result in inhibition of CH(4) production in the 30 degrees C incubations, but transiently inhibited the 15 degrees C 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 15 degrees C 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 30 degrees C incubations, on the other hand, the relative gene frequency of archaeal members showed the opposite temporal trend or remained constant unlike the 15 degrees C incubations. Again, high-T stress tended to reverse these trends, but the observed effects were much smaller in the 30 degrees C incubations than in the 15 degrees C incubations. In conclusion, a brief high-T stress affected structure and function of the methanogenic archaeal community of rice field soil.