A quantitative proteomic analysis of the heat stress response in Clostridium difficile strain 630.

Clostridium difficile is a serious nosocomial pathogen whose prevalence worldwide is increasing. Post genomic technologies can now be deployed in order to develop understanding of the evolution and diversity of this important human pathogen, yet little is known about the adaptive ability of C. difficile. We used iTRAQ labelling and 2D-LC-MS/MS driven proteomics to investigate the response of C. difficile 630 to a mild, but clinically relevant heat stress. A statistically validated list of 447 proteins to which functional roles were assigned was generated, allowing reconstruction of central metabolic pathways including glycolysis, gamma-aminobutyrate metabolism and peptidoglycan biosynthesis. Some 49 proteins were significantly modulated under heat stress: classical heat shock proteins including GroEL, GroES, DnaK, Clp proteases and HtpG were upregulated in addition to several stress inducible rubrerythrins and proteins associated with protein modification, such as prolyl isomerases and proline racemase. The flagellar filament protein, FliC was downregulated, possibly as an energy conservation measure, as was the SecA1 preprotein translocase. The upregulation of hydrogenases and various oxidoreductases suggests that electron flux across these pools of enzymes changes under heat stress. This work represents the first comparative proteomic analysis of the heat stress response in C. difficile strain 630, complementing the existing proteomics datasets and the single microarray comparative analysis of stress response. Thus we have a benchmark proteome for this pathogen, leading to a deeper understanding of its physiology and metabolism informed by the unique functional and adaptive processes used during a temperature upshift mimicking host pyrexia.