Induction of RpoS-dependent functions in glucose-limited continuous culture: what level of nutrient limitation induces the stationary phase of Escherichia coli?
treA and osmY expression and RpoS protein levels were investigated in glucose-limited continuous culture. The level of induction of these stationary-phase markers became as high during growth at a D of 0.1 to 0.2 h(-1) as in carbon-starved batch cultures but only in rpoS+ bacteria. The stress protectant trehalose was actually produced at higher levels at low growth rates than in stationary-phase cultures. The pattern of induction of RpoS-dependent activities could be separated from those regulated by cyclic AMP (cAMP) or endoinduction, and the induction occurred at extreme glucose limitation. Escherichia coli turns to a protective stationary-phase response when nutrient levels fall below approximately 10(-7) M glucose, which is insufficient to saturate scavenger transporters regulated by cAMP plus endoinducers, and this response is optimally expressed at 10(-6) M glucose. The high-level induction of protective functions also explains the maintenance energy requirement of bacterial growth at low dilution rates.
Notley
L
L
Department of Microbiology, University of Sydney, New South Wales, Australia.
Ferenci
T
T
D001426:Bacterial Proteins / Q000032:analysis* / Q000096:biosynthesis; D002352:Carrier Proteins / Q000096:biosynthesis; D000242:Cyclic AMP / Q000378:metabolism; D004186:Disaccharidases / Q000096:biosynthesis; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism*; D033902:Periplasmic Binding Proteins; D012808:Sigma Factor / Q000032:analysis*; D015398:Signal Transduction; D014199:Trehalose / Q000032:analysis
D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D033902:Periplasmic Binding Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; C074783:osmY protein, E coli; D014199:Trehalose; D000242:Cyclic AMP; D004186:Disaccharidases; C040631:alpha, alpha-phosphotrehalase; D005947:Glucose