Susceptibility and resilience of the soil ciliate community to high temperatures

Ciliates play important ecological roles as microbial predators in soil. Although arable soils can experience a wide range of temperatures caused by agricultural land management, the effect of temperature on soil ciliates has been poorly documented, particularly for high temperatures over 30°C. Here, we studied the response of the soil ciliate community to different temperatures in comparison with that of the bacterial and fungal communities. Soils collected from a greenhouse were supplemented with organic fertilizer and incubated at different temperatures (10–60°C). Ciliate trophozoites were detected in the pore water of the soils incubated at 20°C and 10°C, while no trophozoites were observed at temperatures of 30°C and higher. The diversity of the ciliate community represented by fingerprints of denaturing gradient gel electrophoresis (DGGE) also decreased at temperatures higher than 20°C. A few DGGE bands were exclusively dominated at 40°C. The ciliate community composition in the soil incubated at 40°C recovered after subsequent incubation at 20°C, suggesting the resilience of the ciliate community to heat stress. Such recovery was not observed in the soil incubated at 60°C, probably because of the lethal effect on most soil ciliates. The responses of the ciliate community to temperature were similar to those of the fungal community, while the bacterial community showed higher resistance and resilience than the ciliate and fungal communities. The results suggested that temperature is an important factor controlling the ciliate community and affects the structure and functions of the soil microbial food web.