Invariance of the nucleoside triphosphate pools of Escherichia coli with growth rate

The ATP and GTP pools of Escherichia coli have recently been reported to increase approximately 10-fold with increasing growth rates in the range from 0.4 to 1.4 generations/hour (Gaal, T., Bartlett, M. S., Ross, W., Turnbough, C. L., and Gourse, R. L. (1997) Science 278, 2092-2097), Moreover, it was proposed that this variation of the nucleotide pools, particularly the ATP pool, might be responsible for the well known growth rate-dependent regulation of rRNA synthesis in E. coli, To test this hypothesis we have measured the nucleoside triphosphate pools as a function of growth rate for several E, coli strains. We found that the size of all four RNA precursor pools are essentially invariant with growth rate, in the range from 0.5 to 2.3 generations/hour. Nevertheless we observed the expected growth rate-dependent increase of RNA accumulation in these strains. In light of these results, it seems unlikely that nucleotide pool variations should be responsible for the growth rate-dependent regulation of rRNA synthesis.