Growth phase-coupled alterations in cell structure and function of Escherichia coli.

Escherichia coli cultures can be fractionated into more than 20 cell populations, each having a different bouyant density and apparently representing a specific stage of cell differentiation from exponential growth to stationary phase (H. Makinoshima, A. Nishimura, and A. Ishihama, Mol. Microbial. 43:269-279, 2002). The density increase vas found to be impaired at an early step for a mutant E. coli with the disrupted rpoS gene, which encodes the RNA polymerase RpoS(sigma-far stationary-phase gene transcription. This finding suggests that RpoS need far the entire press of cell density increase. In the absence of RpoF sigma factor, the flagella are not formed as observed lay electron microscopy, but the growth phase-coupled density increase takes place as ire wild-type E. coli, confirming that the alteration in cell density as not directly correlated with the presence or absence of flagella. In the stationary-phase cells, accumulation of electron-dense areas was observed by electron microscopic observation of bacterial than sections. By chemical determination, the increase in glycogen (or polysaccharides) was suggested to be one component, which contributes to the increase in weight-to-volume ratio of stationary-phase E. coli cells.