Abstract
The expression and transcriptional regulation of the Escherichia
coli cyx-appA operon and the appY gene has been investigated
during different environmental conditions using single copy
transcriptional lacZ fusions. The cyx-appA operon encodes acid
phosphatase and a putative cytochrome oxidase.ArcA and AppY
activated transcription of the cyx-appA operon during entry into
stationary phase and under anaerobic growth conditions. The
expression of the cyx-appA operon was affected by the anaerobic
energy metabolism.The presence of the electron acceptors nitrate
and fumarate repressed the expression of the cyx-appA operon. The
nitrate repression was partially dependent on NarL. A high
expression of the operon was obtained in glucose medium
supplemented with formate, where E.coli obtains energy by
fermentation. The formate induction was independent of the fhlA
gene product. The results presented in this paper indicate a clear
difference in the regulation of the cyx-appA operon compared to
the cyd operon, encoding the cytochrome d oxidase complex. The
results suggest that cytochrome x oxidase has a function at even
more oxygen limiting conditions than cytochrome d oxidase. The
expression of the appY gene is induced immediately by anaerobiosis
and this anaerobic induction is independent of Fnr, and AppY, but
dependent on ArcA. The expression of the appY gene is not affected
significantly by the anaerobic energy metabolism i.e. fermentation
vs. anaerobic respiration. A model is presented incorporating the
anaerobic regulation of the appY gene and the two operons which
are controlled by AppY: The hydrogenase 1 (hya) operon, and the
acid phosphatase (cyx-appA) operon. The expression of the appY
gene is inversely correlated to the growth rate, and is induced by
phosphate starvation as well as during entry into stationary
phase. During oxygen limiting conditions the stationary phase
induction is partially dependent on ArcA. The alternative sigma
factor SigmaS has limited influence on the transcription of the
appY gene during entry into stationary phase, and no effect on the
induction by phosphate starvation.Lone Brøndsted and Tove Atlung.
1996. Effect of growth conditions on the expression of the acid
phosphatase operon (cyx-appA) and the appY gene, which encodes a
transcriptional activator for expression of the anaerobic and
growth phase activator AppY of Escherichia coli. J. Bacteriol.
178:1556-1564.
Original language | English |
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Journal | Journal of Bacteriology |
Volume | 178 |
Issue number | 6 |
Pages (from-to) | 1556-1564 |
ISSN | 0021-9193 |
Publication status | Published - 1996 |