Open AccessInduction of RpoS-dependent functions in glucose-limited continuous culture: what level of nutrient limitation induces the stationary phase of Escherichia coli?
Author(s) -
Lucinda Notley,
Thomas Ferenci
Publication year - 1996
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.178.5.1465-1468.1996
Subject(s) - rpos , biology , escherichia coli , stationary phase , trehalose , bacteria , bacterial growth , biochemistry , enterobacteriaceae , microbiology and biotechnology , gene expression , gene , genetics , chromatography , chemistry , promoter
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.