EXPRESSION AND ROLE OF THE UNIVERSAL STRESS PROTEIN, USPA, OF ESCHERICHIA-COLI DURING GROWTH ARREST

The synthesis of the small, cytoplasmic protein UspA universal stress protein A) of Escherichia coli is induced as soon as the cell growth r ate falls below the maximal growth rate supported by the medium, regar dless of the condition inhibiting growth. The increase in UspA synthes is appears to be the result of induction of the monocistronic uspA gen e. Induction of this gene during a heat-shock treatment is demonstrate d to be the result of transcriptional activation of a sigma(70)-depend ent promoter which has previously been shown to be activated also duri ng carbon starvation-induced growth arrest. Mutant cells lacking UspA grow at rates indistinguisible from the isogenic parent at different t emperatures and in the presence of different growth inhibitors but are impaired in their ability to survive prolonged periods of complete gr owth inhibition caused by a variety of diverse stresses, including CdC l2, H2O2 DNP, CCCP exposure, and osmotic shock. Moreover, the uspA mut ation results in an increased sensitivity of cells to carbon-source st arvation (i.e. glucose, glycerol or succinate depletion). Also, the mu tation causes a marked alteration in the timing of starvation protein expression but protein expression during steady-state growth appears t o be normal. The results presented have prompted us to postulate that UspA may have a general protective function related to the growth arre st state.