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Journal of Bacteriology, May 2001, p. 2910-2917, Vol. 183, No. 9
INSERM U447, Institut Pasteur de Lille, 59019 Lille Cedex, France
Received 25 September 2000/Accepted 30 January 2001
A new gene from Bordetella bronchiseptica, bfrZ
encoding a putative siderophore receptor, was identified in a
Fur-repressor titration assay. A bfrZ null mutant was
constructed by allelic exchange. The protein profile of this mutant is
similar to that of the wild-type parent strain. The
BfrZ
0021-9193/01/$04.00+0 DOI: 10.1128/JB.183.9.2910-2917.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Expression of the Putative Siderophore Receptor Gene
bfrZ Is Controlled by the Extracytoplasmic-Function
Sigma Factor BupI in Bordetella bronchiseptica
and
-BfrZ+ isogenic pair was tested for
utilization of 132 different siderophores as iron sources. None of
these iron sources acted as a ligand for BfrZ. Translational
bfrZ::phoA and transcriptional
bfrZ::lacZ fusions were introduced
into the B. bronchiseptica bfrZ locus. No alkaline
phosphatase or
-galactosidase activity was detected. Sequence
analysis of the bfrZ upstream region revealed the presence of two tightly linked genes, bupI and bupR.
Both of these genes are located downstream from a Fur-binding sequence.
BupI is homologous to Escherichia coli FecI and
Pseudomonas putida PupI and belongs to the family of
extracytoplasmic-function sigma factors involved in transcription of
genes with extracytoplasmic functions. BupR is homologous to the FecR
and PupR antisigma factors and is predicted to be localized in the
inner membrane. Similar to the surface signaling receptors FecA and
PupB, BfrZ bears an N-terminal extension. We found that
bfrZ is not transcribed when bupI and
bupR are expressed at the same level. However,
overexpression of bupI from a multicopy plasmid triggers
bfrZ transcription, and under these conditions BfrZ was
detected in membrane fractions. By analogy with the FecI-FecR-FecA and
PupI-PupR-PupB systems, our data suggest that bfrZ
expression is inducible by binding of the cognate ligand to BfrZ and
transduction of a signal through the envelope.
*
Corresponding author. Mailing address: INSERM U447,
Institut Pasteur de Lille, 59019 Lille Cedex, France. Phone: (33) 3 20 87 11 51. Fax: (33) 3 20 87 11 58. E-mail:
camille.locht{at}pasteur-lille.fr.
Present address: INSERM CJF 9606, Faculté de Médecine,
13385 Marseille Cedex 05, France.
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