| Summary: | Clostridium difficile has raised significant public concern over the past few decades owing to its emergence as a serious and life-threatening nosocomial pathogen. C. difficile-associated disease is often precipitated due to persistent use of broad-spectrum antibiotics which eventually disrupts the normal colonic micro flora thereby promoting the spread of this toxin- producing organism. There are several classical signs and symptoms associated with C. difficile infection including profuse diarrhoea, abdominal cramps, nausea, and fever. The main objective of this investigation was to employ a systems biology approach in order to assess the response of C. difficile strain 630 when exposed to a clinically relevant heat-stress (4l0C relative to 37°C). This was achieved by carrying out gel-based and gel-free proteomic techniques to characterise the soluble subproteome of this bacterium. Several differentially expressed proteins were hence identified, functionally categorised, and physiochemically characterised which made it possible to comment upon the biochemistry of this organism when exposed to heat-stress conditions. Subsequently, in order to complement our proteomics dataset, whole-genome microarrays were performed to gain a transcriptomic overview of the same heat-stress response of C. difficile. Upon data analysis, it was revealed that in addition to several others, the gene expression and protein abundance levels of classical molecular chaperones such as GroEL and DnaK were significantly modulated. Therefore, genes encoding these chaperones were then targeted to attempt and isolate knockout mutants of C. difficile in order to assess the impact of such a disruption upon the overall physiology of this organism. The results obtained from this systems biology investigation provide a comprehensive overview of the heat-stress response of C. difficile and additionally reveals the importance of certain genes in maintaining cellular homeostasis not only upon exposing the organism to stressful environments, but also under optimal growth conditions.
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