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Molecular mechanisms of Campylobacter jejuni survival : characterization of the CprRS two-component regulatory system and biofilm formation Svensson, Sarah Lauren

Abstract

Campylobacter jejuni is the leading cause of foodborne bacterial gastroenteritis in the developed world. Although illness is usually self-limiting, immunocompromised individuals are at risk for infections recalcitrant to antibiotic treatment. Prior infection with C. jejuni also correlates with serious sequelae such as Guillain-Barré syndrome. The success of C. jejuni as a zoonotic pathogen indicates it can adapt to varied conditions encountered during pathogenesis, despite apparent fastidiousness in the lab. Understanding how C. jejuni survives in common reservoirs may allow development of strategies to limit survival in infection reservoirs or during pathogenesis, and greatly reduce the impact of C. jejuni-mediated disease. A two-component regulatory system, (CprRS; Campylobacter planktonic growth regulation) was previously identified in a screen for genes that may be required for adaptation to the host. Subsequent characterization of CprRS has contributed to understanding of two themes related to C. jejuni survival: environmental gene regulation and biofilm formation. The CprR response regulator was essential for viability, and while the CprS sensor kinase was dispensable, a ΔcprS mutant showed significant phenotypic differences from WT. Initial characterization of ΔcprS using phenotypic and proteomic means provided evidence that CprRS affects phenomena related to biofilm formation. Further characterization of CprRS was undertaken through transcriptomics of ΔcprS, molecular analysis of CprR, and promoter analysis. The CprRS regulon suggests that the system may control aspects of the cell envelope, including expression of the HtrA periplasmic protease. Finally, subsequent analysis of the biofilm-enhanced ΔcprS mutant, together with epistatic analyses and analysis of WT C. jejuni under stress conditions, has provided insight into C. jejuni biofilm initiation, maturation, and physiology. A specific role for flagella in biofilm initiation was demonstrated, and lysis and extracellular DNA release during biofilm maturation was also observed. Furthermore, evidence that the C. jejuni biofilm lifestyle confers stress tolerance that is not present in planktonic counterparts was obtained. Characterization of CprRS has thus contributed to knowledge of both physiological and regulatory themes that provide C. jejuni, a pathogen which diverges from paradigms set out in model bacteria, with its surprising resilience during zoonosis, and has also identified novel targets for infection control.

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