Presenter(s): Dan Tudorica
Faculty Mentor(s): Arden Perkins
Oral Session 3 M
The Chemoreceptor Zinc-Binding domain (CZB) is a protein module common in host-associated bacteria that seems to regulate bacterial chemoreceptors that control motility. The ligand these protein domains sense remains uncertain, however CZB domains contain a cysteine that binds to zinc, a chemical moiety that is known to be reactive with bleach (HOCl). Thus, my hypothesis is that CZBs are responsible for sensing HOCl, which is a prevalent antibacterial agent synthesized by human neutrophils to combat infections. Using the fluorescence of a sample of purified CZB, my data indicate the protein’s structure changes in response to physiologically-relevant concentrations of HOCl, consistent with a mechanism for signal transduction. Furthermore, by examining the circular dichroism spectrum of CZB under increasing concentrations of HOCl, I identified this structural change as a loss of alpha-helicity.
I also examined the hardiness of CZB-possessing bacteria in vivo in the presence of varying concentrations of HOCl. I found that the bacterial pathogens Salmonella and Helicobacter pylori, which possess CZB-regulated chemoreceptors, can tolerate acute treatments of HOCl and remain motile, and were more resistant than Escherichia coli, which has a CZB-regulated diguanylate cyclase but lacks a CZB-regulated chemoreceptor. E. coli, however, proved to be more tolerant of surviving high levels of HOCl over 6-12 hours. In summary, my research suggests CZB domains have the surprising capability to sense HOCl, the strongest oxidant generated by the human immune system, and that bacteria that colonize humans may use these sensors for different purposes in their colonization strategies.