E. coli has evolved several mechanisms for surviving low pH stress.  We report that oxalic acid, a small chain organic acid (SCOA), induces a moderate acid-tolerance response (ATR) in two ways.  Adaptation at pH 5.5 with 50 mM oxalate and inclusion of 25 mM oxalate in the pH 3.0 minimal challenge medium separately conferred protection: 67 � 7% and 87 � 17% survival after 2 hours, respectively.  Combination of oxalate-adaptation and oxalate supplementation in the challenge medium resulted in increased survival over adaptation or oxalate in the challenge medium alone.  Cells show significant protection after 15 min exposure to 50 mM potassium oxalate.   This oxalate-dependent ATR is strongest at pH 3.0, but there is also significant, but reduced protection at pH 2.5.  We theorize that this oxalate ATR could enhance the pathogenesis of virulent E. coli consumed with oxalate-containing foods like spinach.

Oxalate-dependent acid tolerance response in Escherichia coli

245th National Meeting (2013)

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