Thermo-osmoregulation of heat-labile enterotoxin expression by Escherichia coli.
Enterotoxigenic Escherichia coli causes diarrhea by producing several virulence factors including heat-labile enterotoxin (LT). LT is maximally expressed at 37 degrees C. The histone-like nucleoid structuring protein (H-NS) appears to inhibit LT expression by binding to a downstream regulatory element (DRE) at low temperatures. An hns+ E. coli strain, X7026, carrying an LT-beta-galactosidase translational fusion plasmid (pLT-lac) was shown to be responsive to varying amounts of sodium chloride (NaCl) as well as sucrose or lithium chloride. Maximal responsiveness to the various osmolytes was obtained with cells grown at 37 degrees C under microaerophilic conditions. Temperature-osmotic upshift experiments demonstrate LT expression is thermo-osmoregulated. pLT-lac was tested in an hns strain or its congenic hns+ strain for its response to NaCl. LT expression is elevated in the hns strain regardless of NaCl concentration and retains its osmoresponsiveness. The response of the DRE deletion plasmid (pLT-lacDeltaNC) to NaCl is similar to that of the undeleted plasmid.
Department of Biology, Long Island University-Brooklyn, 1 University Plaza, Brooklyn, NY 11201, USA. Julie.Trachman@liu.edu
Julie D
JD
Trachman
Munira
M
Yasmin
D019677:Artificial Gene Fusion; D001426:Bacterial Proteins / Q000235:genetics; D001427:Bacterial Toxins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics; D004768:Enterotoxins / Q000235:genetics*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D009154:Mutation; D010957:Plasmids / Q000235:genetics; D012965:Sodium Chloride / Q000494:pharmacology; D013696:Temperature; D014882:Water-Electrolyte Balance; D001616:beta-Galactosidase / Q000235:genetics
D001426:Bacterial Proteins; D001427:Bacterial Toxins; D004268:DNA-Binding Proteins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; C031908:H-NS protein, bacteria; D012965:Sodium Chloride; C027538:heat-labile enterotoxin, E coli; D001616:beta-Galactosidase