Tag: Arden Perkins

Chemoreceptor Zinc-Binding Protein Domains Sense Hypochlorous Acid

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.

The role of the Chemoreceptor Zinc-Binding Domain in bacterial signal transduction

Presenter(s): Dan Tudorica—Biochemistry

Faculty Mentor(s): Arden Perkins

Session 3: The Substance of Us

Previous work presented at the undergraduate research symposium hypothesized that the chemoreceptor zinc-binding (CZB) domain acted to sense bleach in certain bacteria’s environment and correspondingly direct bacterial swimming patterns . This project presents an expanded view of the CZB domain as being responsible not just for informing bacterial swimming patterns in the presence of bleach, but also for regulating the formation and dispersal of bacterial biofilms . Through the use of genetically-modified bacteria and biofilm-quantification assays, we determined that bleach in the bacteria’s environment encourages the formation of biofilms . In addition, we find that modifying the active site of the CZB domain in such a way as to make the domain “always on” increases the amount of biofilm produced by the bacteria in a fashion largely insensitive to subsequent addition of bleach . This evidence suggests that the CZB domain, known to regulate bacterial swimming patterns, is also used by bacteria to modulate the amount of biofilm that they form . This work helps us understand the biochemistry of how bacteria, particularly gut-colonizing human pathogens, behave in order to survive and thrive in their environment, possibly setting the groundwork for future therapeutic interventions .