Abstract
Strains of Escherichia coli K-12, O157:H7, and Shigella flexneri grown to stationary phase in complex unbuffered media can survive for several hours at pH 2.5. This stationary-phase acid resistance phenotype is dependent upon the alternate sigma factor sigmas and the supplementation of either glutamate or glutamine in the acidified media used for acid challenge. Acid resistance under these defined conditions can be inhibited by the glutamate analog L-trans-pyrrolidine-2,4-dicarboxylic acid which blocks uptake of glutamate/glutamine by selective inhibition. The gadC gene, encoding an inner membrane antiporter essential for the expression of acid resistance, could not be detected in other family members of the Enterobacteriacae.
MeSH terms
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Acids / metabolism
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Bacterial Proteins*
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Culture Media
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DNA, Bacterial / analysis
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Dicarboxylic Acids / pharmacology*
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Escherichia coli / drug effects*
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Escherichia coli / genetics
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Escherichia coli / metabolism*
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Escherichia coli Proteins*
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Glutamic Acid / analogs & derivatives
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Glutamic Acid / metabolism
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Glutamine / metabolism
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In Vitro Techniques
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Membrane Proteins / genetics
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Membrane Proteins / metabolism
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Neurotransmitter Uptake Inhibitors / pharmacology*
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Phenotype
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Plasmids
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Pyrrolidines / pharmacology*
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Shigella flexneri / drug effects*
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Shigella flexneri / genetics
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Shigella flexneri / metabolism*
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Sigma Factor / metabolism
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gamma-Aminobutyric Acid / metabolism
Substances
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Acids
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Bacterial Proteins
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Culture Media
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DNA, Bacterial
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Dicarboxylic Acids
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Escherichia coli Proteins
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GadC protein, E coli
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GadC protein, bacteria
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Membrane Proteins
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Neurotransmitter Uptake Inhibitors
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Pyrrolidines
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Sigma Factor
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Glutamine
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Glutamic Acid
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gamma-Aminobutyric Acid
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pyrrolidine-2,4-dicarboxylic acid