Title:
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Response of Camlylobacter jejuni to oxygen limitation and the caecal environment
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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.
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