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Journal of Bacteriology, October 1998, p. 5291-5298, Vol. 180, No. 20
Department of Genetics, University of
Leicester, Leicester LE1 7RH, United Kingdom
Received 20 March 1998/Accepted 5 August 1998
The expression of iron-regulated systems in gram-negative bacteria
is generally controlled by the Fur protein, which represses the
transcription of iron-regulated promoters by using Fe2+ as
a cofactor. Mutational analysis of the Campylobacter jejuni fur gene was carried out by generation of a set of mutant copies of fur which had a kanamycin or chloramphenicol resistance
gene introduced into the regions encoding the N and C termini of the Fur protein. The mutated genes were recombined into the C. jejuni NCTC 11168 chromosome, and putative mutants were confirmed
by Southern hybridization. C. jejuni mutants were obtained
only when the resistance genes were transcribed in the same orientation as the fur gene. The C. jejuni fur mutant grew
slower than the parental strain. Comparison of protein profiles of
fractionated C. jejuni cells grown in low- or high-iron
medium indicated derepressed expression of three iron-regulated outer
membrane proteins with molecular masses of 70, 75, and 80 kDa.
Characterization by N-terminal amino acid sequencing showed the 75-kDa
protein to be identical to CfrA, a Campylobacter coli
siderophore receptor homologue, whereas the 70-kDa protein was
identified as a new siderophore receptor homologue. Periplasmic
fractions contained four derepressed proteins with molecular masses of
19, 29, 32, and 36 kDa. The 19-kDa protein has been previously
identified, but its function is unknown. The cytoplasmic fraction
contained two iron-repressed and two iron-induced proteins with
molecular masses of 26, 55, 31, and 40 kDa, respectively. The two
iron-repressed proteins have been previously identified as the
oxidative stress defense proteins catalase (KatA) and alkyl
hydroperoxide reductase (AhpC). AhpC and KatA were still iron regulated
in the fur mutant, suggesting the presence of
Fur-independent iron regulation. Further analysis of the C. jejuni iron and Fur regulons by using two-dimensional gel
electrophoresis demonstrated the total number of iron- and Fur-regulated proteins to be lower than for other bacterial pathogens.
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Iron-Responsive Gene Regulation in a Campylobacter
jejuni fur Mutant

and
*
Corresponding author. Mailing address: Department of
Genetics, University of Leicester, University Road, Leicester LE1 7RH, United Kingdom. Phone: 44-116-2523434. Fax: 44-116-2523378. E-mail: ket{at}le.ac.uk.
Present address: Department of Medical Microbiology, Faculty of
Medicine, Vrije Universiteit Amsterdam, 1081 BT Amsterdam, The
Netherlands.
Present address: Meningococcal Research Group, Division of
Microbiology, University Hospital, Nottingham NG7 2UH, United
Kingdom.
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