RpoS-independent and growth phase-dependent expression of dcuSR operon of Escherichia coli

Abo-Amer, A. E. and Altalhi, A. D. (2009) RpoS-independent and growth phase-dependent expression of dcuSR operon of Escherichia coli. Acta Microbiologica et Immunologica Hungarica, 56 (3). pp. 211-227. ISSN 1217-8950

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Abstract

The dcuSR operon of Escherichia coli encodes a two-component sensor/kinase-response/regulator system. This system regulates gene expression in response to external C4-dicarboxylates. During entry into stationary phase Gram-negative bacteria express genes that impart cellular resistance to environmental stresses. In E. coli , 50 or more genes are triggered by sigma factor ( σs) during entry into stationary phase. Multi-copy dcuS-lacZ and chromosomally integrated dcuS-lacZ fusions analysis showed that the expression of dcuSR is positively regulated during growth phase. Many genes that are required for stationary-phase adaptation are controlled by RpoS, a conserved alternative sigma factor, whose expression is, in turn, controlled by many factors. To understand whether the dcuSR is dependent upon RpoS, a RpoS- dcuS-lacZ strain was generated. β -Galactosidase assay and Western blot analysis reported that the generated RpoS- dcuS-lacZ strain and the wild type showed the same expression during stationary phase. Surprisingly, the growth phase-dependence of the expression of dcuSR is still present in RpoS- dcuS-lacZ strain suggesting that other growth-phase-dependent regulatory mechanisms (might be the DcuSR system or cAMP/CRP), in addition to RpoS, may control post-exponential dcuSR expression.

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