Regulation of the glutamate-dependent acid-resistance system of diarrheagenic Escherichia coli strains.
The ability to withstand an acid challenge of pH 2.5 or less by Escherichia coli strains is a trait generally believed to be restricted to their stationary phase of growth. Of the three distinct acid-resistance systems that have been identified in E. coli, the glutamate-dependent acid resistance (GAD) system provides the highest level of acid resistance. Earlier reports indicated that in the exponential growth phase of E. coli K-12 strains the GAD system is not active. The present study reports that when grown on minimal medium several diarrheagenic and K-12 strains of E. coli have a complete set of induced genes necessary for GAD in the exponential growth phase to overcome the acid challenge of pH 2.5 for several hours. A previously identified factor(s) specific to the GAD system in the stationary phase and predicted to undergo dilution during the exponential phase appears to be glutamate-decarboxylase isozyme(s) inactivated differentially in the rich vs. minimal growth media.
Bhagwat
Arvind A
AA
Produce Quality and Safety Laboratory, Henry A. Wallace Beltsville Agricultural Research Center, Agricultural Research Service, USDA, Bldg. 002, 10300 Baltimore Avenue, Beltsville, MD 20705-2350, USA. bhagwat@ha.ars.usda.gov
D000143:Acids / Q000378:metabolism / Q000494:pharmacology*; D003470:Culture Media / Q000737:chemistry; D003967:Diarrhea / Q000382:microbiology*; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D018698:Glutamic Acid / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration
D000143:Acids; D003470:Culture Media; D018698:Glutamic Acid