Understanding the osmotic regulation of the proU operon and the prop protein in Salmonella enterica serovar typhimurium
Abstract
Environmental osmotic strength is one of the influential factors controlling how well an organism can survive in its habitat. When an organism is subjected to an increase in the extracellular concentration of solutes impermeable to the cell, it is under osmotic stress and is vulnerable to cell shrinkage. In order to survive, the cell must respond by accumulating compatible solutes. The model organism Salmonella typhimurium contains two compatible solute transporters, ProU and ProP. ProU is an ABC transport system encoded by an operon whose transcription is induced more than 600-fold by osmotic stress. Alignments identified oddly conserved regions directly upstream of the promoter and in the spacer sequence of proU. Random site-directed mutagenesis has shown nucleotides in the spacer sequence are important for general transcription while the nucleotides upstream of the promoter are essential for optimal osmotic induction and represent a novel form of gene regulation. The ProP protein is an integral membrane H+-solute symporter that is able to sense and increase its transport activity in response to osmotic stress; however the mechanism by which this is accomplished is unknown. Mutations in the ProP protein were randomly generated and mapped to the proP gene by classical bacterial genetic mapping. The gene was PCR amplified, and sequenced as part of a unique introductory freshman lab module where students had the opportunity to both learn basic introductory freshmen biology lab skills while taking part in an authentic research project. The efficacy of incorporating an authentic research project into an introductory biology lab and the effect it has on improving critical thinking skills was assessed. The results of this project will be published in a peer-reviewed journal with the students listed as co-authors. Further characterization of these mutants suggests they have different effects on the function of ProP.
Degree
Ph.D.
Advisors
Csonka, Purdue University.
Subject Area
Molecular biology|Genetics|Microbiology
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