Chris Vriezen
cvriezen@microbio.umass.edu

Responses to desiccation of rhizobia

My interest is the response to water stress of soil microorganisms. S. meliloti is such a common soil microorganism and is generally studied for its ability to fix atmospheric nitrogen in root nodules and to supply this biologically available nitrogen to the plant. This interaction between microbe and plant host (alfalfa) is severely affected by NaCl stress and desiccation. Additionally, salt and desiccation stress affect the ability of rhizobia to survive in the soil. Interestingly however, for some rhizobia, an increase in survival after desiccation can be observed when exposed to NaCl. S. meliloti 1021 is such a strain (see figure). This observation indicates that there is a common overlap in response to NaCl and the ability to survive desiccation. Protection by solutes outside the cells can be excluded since many rhizobia do not show this response. My goal is to find a gene responsible for the ability to survive NaCl mediated survival during desiccation.