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Title: Response of Camlylobacter jejuni to oxygen limitation and the caecal environment
Author: Ramirez, Carlos Avila
ISNI:       0000 0004 2743 8598
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2012
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Campylobaeter jejuni is the major cause of acute gastroenteritis in the developed world. It is usually acquired through contaminated poultry as C. jejuni causes a silent asymptomatic infection of the chicken. Pathogens face different sources of stress during its transit through the gut. Nitrosative Stress (NS) is part of the host-mediated response against infection. Early work from the Park group identified the Campylobaeter haemoglobin (Cgb) to be regulated by NssR in response to nitrosative stress in microaerobic cultures of C jejuni. However, oxygen-limited cultures of C. jejuni arc more sensitive to NO than microaerobic cultures and Cgb has been shown to be much less expressed in response to nitrosative stress. C. jejuni also possess a truncated haemoglobin, Ctb, which was thought to mediate the oxygen-limited response to NO as it was seen up-regulated in microarray studies. The nitrite reductase, NrfA, was also considered as an important NO detoxification mechanism for oxygen-limited C. jejuni. In this work, we study the response of oxygen-limited C. jejuni to nitrosative stress. We describe an adaptive response that is independent of NssR, NrfA and Ctb, although a collaborative contribution of NrfA and Ctb to alleviate respiration inhibition by NO is not discarded. We propose that the cyanide insensitive oxidase, CioAB, has a NO-reductase function as cyanide-inhibited cell suspensions are able to detoxify NO faster than untreated suspensions, independently of strain or pre- treatment. We also observe that the oxygen-limited C jejuni reaction to NO is similar to the ehanges occurring during colonization. Finally, we explore an innovative model of signal recognition during colonization. We use a diffusion capsule to feed small, diffusible molecules from chicken caecal matter into a microaerobic C. jejuni culture to study the transcriptomic chances mounted as response to chemical signals present in the chicken gut. We find that in early stages of exposure to the caecal contents (10 min) the dual component colonization regulator, deeR, plays an important yet not fully understood role.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available