Characterization of the heat-shock circuit in Campylobacter jejuni

This thesis consists of two different works developed on two distinct research themes, both of them included in the broader issue of bacterial virulence. The first part concerns the molecular characterization of the heat-shock regulatory circuit in the food-borne pathogen Campylobacter jejuni. The heat-shock response, being cellular damage protection mechanism, is involved in the establishment of successful infections in different bacteria. Moreover, in C. jejuni, this regulatory circuit emerged as a crucial pathway for the shift between commensalism and pathogenicity in different hosts, tanks to the peculiarity to modulate host-pathogen interactions. This evidence makes the heat-shock circuit characterization indispensable to elucidate the molecular basis of C. jejuni pathogenicity and virulence. In the human pathogen C. jejuni, the response to thermic stress is controlled by a regulatory circuit, which acts at the transcriptional level and involves the repressors HspR and HrcA. To characterize the molecular mechanism underpinning HspR and HrcA regulatory function, we investigated in detail the HspR and HrcA interactions with target promoter regions. The characterization allowed the identification of their binding sites, and highlight a complex architecture resulting from protein-DNA interactions. The second section is inherent to urease activity in the presence of gold-based compounds. The urease enzyme is a virulence factor for different pathogenic bacteria, of which Helicobacter pylori, Mycobacterium tuberculosis, Cryptococcus neoformans, Yersinia pestis, and Proteus mirabilis. This peculiarity makes the urease an interesting target for potential new specific-drugs against ureolytic pathogens. In this work, we analysed the inhibition ability of different gold-based compounds on urease, investigating the potentiality of these compounds as future antimicrobials in ureolytic bacteria.