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J. Bacteriol., Nov 1995, 6477-6485, Vol 177, No. 22
MA Uhl and JF Miller
BvgA and BvgS, which regulate virulence gene expression in Bordetella
pertussis, are members of the two-component signal transduction family. The
effects of growth conditions on the ability of BvgAS to activate
transcription of fhaB (encoding filamentous hemagglutinin) and ptxA
(encoding the S1 subunit of pertussis toxin) were assessed in Escherichia
coli by using chromosomal fhaB-lacZYA and ptxA-lacZYA fusions. Although it
had previously been reported that a ptxA-lacZYA transcriptional fusion was
not activated by bvgAS in E. coli (J. F. Miller, C. R. Roy, and S. Falkow,
J. Bacteriol. 171:6345-6348, 1989), we now present evidence that ptxA is
activated by bvgAS in E. coli in a manner that is highly dependent on the
growth conditions. Higher levels of beta-galactosidase were produced by
ptxA-lacZYA in the presence of bvgAS during growth in Stainer-Scholte
medium or M9 minimal salts medium with glucose than in Luria-Bertani
medium. In contrast, the level of fhaB-lacZYA expression was high during
growth in all media. Addition of modulating stimuli which inhibit BvgAS
function eliminated expression of ptxA-lacZYA. Levels of beta-galactosidase
expressed from the ptx-lacZYA fusion correlated with growth rate and with
the final optical density at 600 nm, suggesting that the lower growth rate
in M9- glucose and Stainer-Scholte media was responsible for greater
accumulation of beta-galactosidase than was seen in Luria-Bertani medium.
Overproduction of BvgA was not sufficient for activation of ptxA expression
but was sufficient for fhaB expression.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
BvgAS is sufficient for activation of the Bordetella pertussis ptx locus in Escherichia coli
Department of Microbiology and Immunology, School of Medicine, University of California, Los Angeles 90024, USA.
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