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J. Bacteriol., Jul 1996, 3727-3735, Vol 178, No. 13
CC Sze, T Moore and V Shingler
Transcription from Pseudomonas-derived -24, -12 Po promoter of the
pVI150-encoded dmp operon is mediated by the sigma 54-dependent DmpR
activator in response to the presence of aromatic pathway substrates in the
medium. However, global regulatory mechanisms are superimposed on this
regulatory system so that the specific response to aromatic effectors is
absent in cultures until the stationary phase is reached. Here we
genetically dissect the system to show that the growth phase response is
faithfully mimicked by a minimal system composed of the dmpR regulatory
gene and the Po promoter regulatory region and can be reproduced in
heterologous Escherichia coli. Using this system, we show that the growth
phase-dependent DmpR-mediated response to aromatic compounds is limited to
fast-growing cultures. Thus, during exponential growth of cultures in
minimal media containing different carbon sources, the response to
aromatics is immediate, while the response is suppressed in cultures grown
on rich media until the exponential-to- stationary phase transition.
Elements known to be involved in the DmpR- mediated transcription from Po
were analyzed for the ability to influence the growth phase response. Most
dramatically, overexpression of DmpR was shown to completely abolish the
growth phase response, suggesting that a negatively acting factor may
mediate this level of regulation. The possible mechanism of action and
integration (of the specific regulation of the dmp operon-encoded catabolic
enzymes with the physiological status of the bacteria are discussed.
Copyright © 1996, American Society for Microbiology
Growth phase-dependent transcription of the sigma(54)-dependent Po promoter controlling the Pseudomonas-derived (methyl)phenol dmp operon of pVI150
Department of Cell and Molecular Biology, Umea University, Sweden.
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