Affiliation:
1. Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, P.O. Box 56, Dunedin, New Zealand
Abstract
ABSTRACT
The uptake of phosphate into the cell via high-affinity, phosphate-specific transport systems has been studied with several species of mycobacteria. All of these species have been shown to contain several copies of such transport systems, which are synthesized in response to phosphate limitation. However, the mechanisms leading to the expression of the genes encoding these transporters have not been studied. This study reports on the investigation of the regulation of the
pstSCAB
and the
phnDCE
operons of
Mycobacterium smegmatis
. The
phn
locus contains an additional gene,
phnF
, encoding a GntR-like transcriptional regulator. Expression analyses of a
phnF
deletion mutant demonstrated that PhnF acts as a repressor of the
phnDCE
operon but does not affect the expression of
pstSCAB
. The deletion of
pstS
, which is thought to cause the constitutive expression of genes regulated by the two-component system SenX3-RegX3, led to the constitutive expression of the transcriptional fusions
pstS
-
lacZ, phnD
-
lacZ
, and
phnF
-
lacZ
, suggesting that
phnDCE
and
phnF
are conceivably new members of the SenX3-RegX3 regulon of
M. smegmatis
. Two presumptive binding sites for PhnF in the intergenic region between
phnD
and
phnF
were identified and shown to be required for the repression of
phnD
and
phnF
, respectively. We propose a model in which the transcription of
pstSCAB
is controlled by the two-component SenX3-RegX3 system, while
phnDCE
and
phnF
are subject to dual control by SenX3-RegX3 and PhnF.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
49 articles.
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