J Bacteriol, February 1998, p. 871-880, Vol. 180, No. 4
0021-9193/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
INSERM U447,
Received 5 September 1997/Accepted 6 December 1997
A Fur titration assay was used to isolate DNA fragments bearing
putative Fur binding sites (FBS) from a partial Bordetella bronchiseptica genomic DNA library. A recombinant plasmid bearing a 3.5-kb DNA insert was further studied. Successive deletions in the
cloned fragment enabled us to map a putative FBS at about 2 kb from one
end. Sequence analysis revealed the presence of an FBS upstream from a
new gene encoding an AraC-type transcriptional regulator. The deduced
protein displays similarity to PchR, an activator of pyochelin
siderophore and ferripyochelin receptor synthesis in Pseudomonas
aeruginosa. Homologous genes in Bordetella pertussis
and Bordetella parapertussis were PCR amplified, and sequence comparisons indicated a very high conservation in the three
species. The B. pertussis and B. bronchiseptica
chromosomal genes were inactivated by allelic exchange. Under low-iron
growth conditions, the mutants did not secrete the alcaligin
siderophore and lacked AlcC, an alcaligin biosynthetic enzyme.
Alcaligin production was restored after transformation with a plasmid
bearing the wild-type gene. On the basis of its role in regulation of
alcaligin biosynthesis, the new gene was designated alcR.
Additional sequence determination showed that alcR is
located about 2 kb downstream from the alcABC operon and is
transcribed in the same orientation. Two tightly linked open reading
frames, alcD and alcE, were identified between alcC and alcR. AlcE is a putative iron-sulfur
protein; AlcD shows no homology with the proteins in the database. The
production of major virulence factors and colonization in the mouse
respiratory infection model are AlcR independent.
*
Corresponding author. Mailing address: INSERM U447,
Institut Pasteur de Lille, 1 rue du Prof. Calmette, BP 245, 59019 Lille Cedex, France. Phone: 33 (0) 3 20 87 11 51. Fax: 33 (0) 3 20 87 11 58. E-mail: Camille.Locht{at}pasteur-lille.fr.
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