Using Ultra Performance Liquid Chromatography-Mass Spectrometric Based Metabolomics to Determine the Metabolic Differences due to Low Temperature or Genetic Mutation in \u3ci\u3eSalmonella enterica\u3c/i\u3e

Metabolomics aims to identify and quantify all of the small molecules within a cell. The relative concentrations of metabolites within cells grown under different experimental conditions, or different species, can be compared using pool size data. Exposing cellular cultures to isotopically labeled compounds allows the progress of metabolites through metabolic pathways to be tracked, known as flux. In the first experiment, the metabolic effects of exposure to lower than optimal temperatures in wild type Salmonella enterica, i.e. cold shock, were determined. The metabolites involved in glycolysis, the citric acid cycle, and the pentose phosphate pathway had less efficient labeling and smaller pool sizes at lower temperatures. Most of the amino acids detected showed less efficient labeling and larger pool sizes at lower temperatures, perhaps indicating that proteins were being broken down into amino acids. Alternatively, the less efficient labeling may be due to enzymes denaturing reducing the catalytic abilities of the cells, a slowdown in the rate of transcription or in the rate of translation. It is important to study cold shock in Salmonella enterica, at three temperatures in which contamination with the pathogen occurs, in order to see if there is a way to kill the pathogenic species more efficiently and limit the people who get ill from consuming Salmonella enterica from food contamination. The second experiment compared the purH mutant and the wild type strain of Salmonella enterica. The purH mutant had the gene that codes for the enzyme AICAR transformylase/IMP cyclohydrolase removed. AICAR is important to study since it is involved in many pathways in diverse organisms, activates AMP-activated protein kinase in mammals, which affects energy balance and the response to metabolic stress, and AICAR accumulation has been linked to an inhibition of the proliferation of cancer cells. Metabolites in glycolysis and the citric acid cycle were found to label less efficiently or have smaller pool sizes in the purH mutant, with the exceptions of those compounds involved in other pathways. The pentose phosphate pathway showed similar labeling patterns and larger pool sizes in the purH mutant, indicating that sugars may be going through the pathway