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.
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
Arvind A
AA
Bhagwat
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