Affiliation:
1. Departamento de Biotecnologı́a Microbiana, Centro Nacional de Biotecnologı́a, CSIC, Campus de la Universidad Autónoma de Madrid, Cantoblanco, 28049—Madrid, Spain
Abstract
ABSTRACT
The AlkS protein activates transcription from the
PalkB
promoter, allowing the expression of a number of genes required for the assimilation of alkanes in
Pseudomonas oleovorans
. We have identified the promoter from which the
alkS
gene is transcribed,
PalkS
, and analyzed its expression under different conditions and genetic backgrounds. Transcription from
PalkS
was very low during the exponential phase of growth and increased considerably when cells reached the stationary phase. The
PalkS
−10 region was similar to the consensus described for promoters recognized by
Escherichia coli
RNA polymerase bound to the alternative sigma factor ς
S
, which directs the expression of many stationary-phase genes. Reporter strains containing
PalkS-lacZ
transcriptional fusions showed that
PalkS
promoter is very weakly expressed in a
Pseudomonas putida
strain bearing an inactivated allele of the gene coding for ς
S
,
rpoS
. When
PalkS
was transferred to
E. coli
, transcription started at the same site and expression was higher in stationary phase only if ς
S
-RNA polymerase was present. The low levels of AlkS protein generated in the absence of ς
S
were enough to support a partial induction of the
PalkB
promoter. The −10 and −35 regions of
PalkS
promoter also show some similarity to the consensus recognized by ς
D
-RNA polymerase, the primary form of RNA polymerase. We propose that in exponential phase
PalkS
is probably recognized both by ς
D
-RNA polymerase (inefficiently) and by ς
S
-RNA polymerase (present at low levels), leading to low-level expression of the
alkS
gene. ς
S
-RNA polymerase would be responsible for the high level of activity of
PalkS
observed in stationary phase.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
34 articles.
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