Escherichia coli and other enteric bacteria enter the stationary phase of the cell cycle at the onset of environmental stress. Cells remain viable because physiological changes occur. Growth slows down or stops. Biosynthetic and catabolic activity is reduced.
Some new activities appear to alleviate osmotic and temperature caused stress.
These processes are controlled by global regulators such as H-NS, the product of the hns gene, Lrp, the product of the lrp gene and sigmas, the product of the rpoS gene. Our laboratory is interested in the mechanism of the down modulation of log phase activities by these three genes. The Lrp protein and the H-NS protein are connected to each other by an unknown mechanism during the stress response. Levinthal et al. Lrp is an activator of the ilvIH genes that are important for isoleucine biosynthesis.