The Role of the EAL-Like Protein STM1344 and Diguanylate Cyclase STM1987 in the Starvation-Stress Response of Salmonella enterica Serovar Typhimurium

Author

Eunice Jacob, University of South Alababma

Date of Award

2012

Document Type

Undergraduate Thesis

Degree Name

BS

Department

Biomedical Sciences

Faculty Mentor

Michael P. Spector

Abstract

Salmonella serovars cause enterocolitis and/or systemic disease in humans and an­imals following consumption of contaminated food or water. During their lifecycle these bacteria encounter stressful environments, e.g., carbon-energy (C-) source starvation. As a result, of C-starvation the bacteria generate a starvation-stress response (SSR). Microar­ray analyses showed that stm1344 and stm1987 are possible SSR genes. The stm1987 gene encodes a GGDEF domain protein that is proposed to be a diguanylate cyclase (DGC), which synthesizes cyclic 5', 3'-diguanylate (c-di-GMP). The stml344 gene prod­uct is a EAL-like domain protein that lacks c-di-GMP phosphodiesterase (PDEA) activity but appears to respond to c-di-GMP levels in the cell. Based upon this, we propose that the STMI987 and STM1344 proteins function in synthesizing or response to c-di-GMP, respectively, during the SSR; and are needed for the development of a maximal SSR in S. Typhimurium. To test this, we compared wild type and mutant (lacking either stml344 or stml 987) log-phase, 5-h C-starved and 24-h C-starved cells for their ability to generate C-starvation-inducible (CSI) cross-resistance to H₂O₂, polymyxinB, or pH 3.3. The data obtained showed that strains lacking the stml344 or stml987 genes were all unable to generate CSI cross-resistance to H₂O₂ or polymyxinB in both 5-h C-starved and 24-h C­ starved when compared to wild type cells. We can conclude from this that c-di-GMP con­trols aspects of CSI cross-resistance to H₂O₂ and polymyxin B but not to pH 3.3. Fur­thermore, the maintenance of appropriate c-di-GMP levels is necessary to the develop­ment of cross-resistance to H₂O₂ and polymyxin B but not pH 3.3. In addition, STM1344 appears to positively control the development of CSI cross-resistance to H₂O₂ and poly­ myxin B, but not pH 3.3, in response to intracellular c-di-GMP levels.

Recommended Citation

Jacob, Eunice, "The Role of the EAL-Like Protein STM1344 and Diguanylate Cyclase STM1987 in the Starvation-Stress Response of Salmonella enterica Serovar Typhimurium" (2012). Digitized Honors Theses (2002-2017). 30.
https://jagworks.southalabama.edu/honors_theses-boundprint/30