LASZLO CSONKA

Professor
765-494-4969
HANS 327A
csonka@purdue.edu

Associated website(s):

PROFESSIONAL FACULTY RESEARCH

(Microbiology) Adaptation to osmotic stress, regulation of thermotolerance, mechanism of transcriptional regulation of Mg ²⁺ genes in Salmonella enterica .

BIO

The major current research effort of our laboratory is the analysis of the regulation of thermotolerance in Salmonella enterica . This project grew out of our long-standing interest in the characterization of the responses of organisms to osmotic stress. One of the unexpected consequences of osmotic stress it that it can dramatically increase the thermotolerance of a wide variety of bacterial species.

At the outset, our goal was to characterize the mechanism of the osmotic stress-dependent regulation of thermotolerance. Toward this end, we isolated mutants of Salmonella enterica serovar Typhimurium that acquired increased thermotolerance in the absence of osmotic stress. Combination of classical genetic mapping, full genomic sequencing, and physiological studies demonstrated that these mutations resulted in high level transcription of one of two genetic elements, the mtgA gene and the mgtCBR operon, both of which encode proteins related to Mg ²⁺ uptake. This divalent cation has been implicated as a regulatory signal for the transcriptional control of virulence genes in Salmonella , and our results now show that Mg ²⁺ homeostasis also plays a role in the regulation of thermotolerance in this organism. We found that these mutations alter the fatty acid composition of the membranes and thereby protect cells from undue leakage of small ions from the cytoplasm that is triggered by high temperature in the wild type. The improved maintenance of membrane integrity in the mutants could account for their enhanced thermotolerance. The aim of our work in the near future will be to identify why increased expression of the Mg ²⁺ transport genes brings about these beneficial changes in membrane composition and to study the mechanism of transcriptional control of Mg ²⁺ transport genes in wild-type Salmonella .

Because Salmonella is the most frequent cause of foodborne bacterial infections and because cooking and other forms of heat treatment are the most economical and simple means of inactivation of food-borne pathogens, potential practical benefit of our research is that it could contribute to the development of more efficient heat treatments for the removal of pathogens in food products .

Grant Support : National Science Foundation IOS-1456829.

Education

Ph.D., Harvard, 1975

Professional Faculty Research

(Microbiology) Adaptation to osmotic stress, regulation of thermotolerance, mechanism of transcriptional regulation of Mg ²⁺ genes in Salmonella enterica .

Recent Publications

Csonka lab publications have a total of 6,613 citations, h-index of 36, as of 01/31/2018 (Google Scholar click here ).

Ebrahimi, A., Csonka, L. N., Alam, M. A. 2018. Analyzing thermal stability of cell membrane of Salmonella using time-multiplexed impedance sensing. Biophys . J . 114:1-10. doi.org/10.1016/j.bpj.2017.10.032.

Gall, A. R., Datsenko, K. A., Figueroa-Bossi, N., Bossi, L., Masuda, I., Hou, Y.-M., Csonka, L. N. 2016. Mg ²⁺ regulates transcription of mgtA in Salmonella Typhimurium via translation of proline codons during synthesis of the MgtL peptide. PNAS 113:15096-15101. This article has been recognized in a commentary: Hughes, K. T. 2016. Mg ²⁺ -dependent translational speed bump acts to regulate gene transcription. Proc. Natl. Sci. U. S. A. 113:14881-14883. doi: 10.1073/pnas.1618222114.