My research interests center around how bacteria adapt to osmotic stress. We have found that Rhizobium meliloti and Salmonella typhimurium accumulate glutamate in response to osmotic stress. We have investigated the mechanism(s) responsible for this excess glutamate. S. typhimurium but not R. meliloti can use proline as an osmoprotectant, small amounts of proline enable the bacteria to grow with inhibitory levels of salts. We are determining why R. meliloti can not, using a combination of biochemical, genetic and physiological approaches. R. meliloti can use proline very well as sole source of carbon and nitrogen. We are also determining if proline metabolism is involved in providing energy for bacteroids in root nodules. This aspect of plant-microbe interaction is investigated with mutant bacteria unable to utilize proline. We also have a project involving studies of the microbial diversity engendered by the addition of irradiated sewage sludge to soils. We have found that in the amended soils, bacteria can utilize more different carbon sources than in control soils. We also find that more bacteria in the amended soils make siderophores perhaps accounting for the greater plant growth observed in amended soils. Very recently, we have initiated a project developing a simple, rapid, inexpensive method to assay toxic chemicals using bacteria as the test organism.

Members of the lab discuss assay results

Publications that represent the work I do: