title: An essential role for the Escherichia coli DnaK protein in starvation-induced thermotolerance, H2O2 resistance, and reductive division.
abstract: During a 3-day period, glucose starvation of wild-type Escherichia coli produced thermotolerant, H2O2-resistant, small cells with a round morphology. These cells contained elevated levels of the DnaK protein, adjusted either for total protein or on a per-cell basis. Immunoprecipitation of [35S]methionine-labeled protein produced by such starving cells demonstrated that DnaK underwent continuous synthesis but at decreasing rates throughout this time. Glucose resupplementation of starving cells resulted in rapid loss of thermotolerance, H2O2 resistance, and the elevated DnaK levels. A dnaK deletion mutant, but not an otherwise isogenic wild-type strain, failed to develop starvation-induced thermotolerance or H2O2 resistance. The filamentous phenotype associated with DnaK deficiency was suppressed by cultivation in a defined glucose medium. When starved for glucose, the nonfilamentous and rod-shaped dnaK mutant strain failed to convert into the small spherical form typical of starving wild-type cells. The dnaK mutant retained the ability to develop adaptive H2O2 resistance during growth but not adaptive resistance to heat. Complementation of DnaK deficiency by using Ptac-regulated dnaK+ and dnaK+J+ expression plasmids confirmed a specific role for the DnaK molecular chaperone in these starvation-induced phenotypes.
authors.affiliation: School of Biological Sciences, University of Nebraska, Lincoln 68588-0118, USA.
authors.forename: D
authors.initials: D
authors.lastname: Rockabrand
authors.forename: T
authors.initials: T
authors.lastname: Arthur
authors.forename: G
authors.initials: G
authors.lastname: Korinek
authors.forename: K
authors.initials: K
authors.lastname: Livers
authors.forename: P
authors.initials: P
authors.lastname: Blum
mesh_terms: D000222:Adaptation, Physiological; D018830:Adhesins, Escherichia coli / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000942:Antigens, Bacterial / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000954:Antigens, Surface / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002455:Cell Division; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins; D036781:Fimbriae Proteins; D005816:Genetic Complementation Test; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D006358:Hot Temperature / Q000009:adverse effects; D006861:Hydrogen Peroxide / Q000633:toxicity; D009154:Mutation
chemical_list: D018830:Adhesins, Escherichia coli; D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; C035391:antigen 987P, E coli; D036781:Fimbriae Proteins; D006861:Hydrogen Peroxide; C063842:dnaK protein, E coli