D 8 - Werner Liesack
Response of paddy soil microbial communities to salt stress
PD Dr. Werner Liesack
Max Planck Institute for Terrestrial Microbiology
Phone: +49 - 6421 - 178720
At least 20% of all irrigated lands in the world are adversely affected by salinity, including a large proportion of the global rice acreage. Salinity has been shown to be among the factors that influence methane emission from wetland rice fields. However, little is known about how soil salinity affects the composition of paddy soil microbial communities and the functioning of their individual members. In a first study, we observed a differential response of the community members to the addition of NaCl. The response was clearly more pronounced on mRNA level than on rRNA level. Clostridiaceae and Methanosarcinaceae were able to adapt to increasing salt stress. This was related to the expression of genes involved in ‘osmotic stress’ and ‘heat shock’ response. By contrast, Ruminococcaceae, Peptococcaceae, Veillonellaceae, Syntrophomonadaceae and in particular Methanocellaceae were not able to compete under salt stress. In the next project period, we intend to expand this research. In slurry experiments, we will test whether the physiological status of the paddy soil microbial community affects the stress response of their individual members. The long-term effect of soil salinity on the microbial communities will be studied in flooded rice microcosms. Finally, microbial communities residing in native saline paddy soils will be analyzed to examine whether a long history of exposure to salt has selected for particular halotolerant populations. This project will be complemented by our ongoing research on the effects of paddy soil drainage, linking oxidative and water stress with the responsive changes in community composition and functioning. Our overall aim is to understand how structure and functioning of paddy soil microbial communities are shaped by environmental factors.