ppGpp-dependent leuO expression in bacteria under stress

Despite the known potential transcription regulatory role of leuO gene prod uct, LeuO, the condition when leuO expresses during bacterial growth cycle remains unclear. Mechanistically, leuO expression was shown to be part of p romoter relay mechanism, however, the factor(s) responsible for the regulat ion of leuO expression is not known. Combining Northern and Western results , we demonstrate in the present communication that leuO expression is norma lly low and enhanced when bacteria are in transition from exponential growt h to stationary phase. The stationary phase-associated leuO expression is p pGpp dependent and rpoS (sigma(s) factor) independent. (C) 2000 Academic Pr ess.