Growth-rate dependent regulation of mRNA stability in Escherichia coli

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Abstract
The rate of production of bacterial gene products is known to vary with the rate of cell growth, the concentrations of many cellular proteins are altered during times of decreased growth rate. In addition, proteins whose in vivo levels show no significant alterations with changes in cell doubling time must be synthesized at rates that vary in direct proportion to the growth rate of the cell. In certain instances, growth-rate dependent gene regulation has been shown to occur at the transcriptional or translational level. Another potentially important element in the regulation of gene expression is the stability of messenger RNA. We report here the effect of bacterial growth rate on the half lives of four different monocistronic Escherichia coli mRNA species. The stabilities of two of these species, the transcripts of the ompA and cat genes, exhibited a marked dependence on cell growth rate, whereas the half lives of the transcripts of the lpp and bla genes are constant over a broad range of cell doubling times. Our results indicate that E. coli can alter the rate of synthesis of certain proteins by modulating mRNA stability in response to changes in the rate of cell growth.