Affiliation:
1. Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN
2. Institute for Animal Health, Compton, Berkshire, RG20 7NN, United Kingdom
Abstract
ABSTRACT
Campylobacter jejuni
is a microaerophilic, asaccharolytic bacterium. The identity of the carbon and energy sources used by
C. jejuni
in vivo is unknown, but the genome sequence of strain NCTC11168 indicates the presence of genes for catabolism of a limited range of amino acids, including serine. Specific omission of
l
-serine from a defined medium containing a mixture of amino acids led to a dramatic decrease in cell yields. As
C. jejuni
does not have a biosynthetic serine requirement, this supports earlier suggestions that
l
-serine is a preferentially catabolized amino acid. Serine transport was found to be mediated by at least two systems in strain 11168; a high-capacity, low-affinity
l
-serine-specific system encoded by
Cj1625c
(
sdaC
) and a higher-affinity
l
-serine/
l
-threonine system responsible for residual
l
-serine transport in an
sdaC
mutant. Catabolism of
l
-serine to pyruvate and ammonia is carried out by SdaA (encoded by
Cj1624c
), which was overexpressed, purified, and shown to be an oxygen-labile iron-sulfur enzyme.
l
-Serine dehydratase activity in an
sdaA
mutant was reduced 10-fold compared to that in the wild type, but the residual activity (due to the anabolic
l
-threonine dehydratase) could not support either growth on or utilization of
l
-serine in defined media. However, although
sdaA
mutants showed no obvious growth defect in complex media, they completely failed to colonize 3-week-old chickens as assayed both by cloacal swabs taken over a 6-week period and by cecal colony counts postmortem. In contrast, the isogenic parent strain colonized chickens to high levels within 1 week of inoculation. The results show that an active SdaA is essential for colonization of the avian gut by
C. jejuni
and imply that catabolism of
l
-serine is crucially important for the growth of this bacterium in vivo.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
129 articles.
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