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. 2004 Sep;186(18):6179–6185. doi: 10.1128/JB.186.18.6179-6185.2004

FIG. 2.

FIG. 2.

Plating assay for acid resistance. The percent survival of E. coli and isogenic dsrA mutants and overexpressers is plotted against time spent at pH 2.0. (A) Comparison of K-12 strain M182 with different levels of DsrA and DsrA*H. Filled circles represent wild-type M182, and open circles represent dsrA::cat, a null variant of M182. Filled triangles represent dsrA::cat complemented with wild-type DsrA from a plasmid; open triangles represent dsrA::cat complemented with the plasmid-encoded dsrA*H variant. Results are the average of three trials. The average standard deviation is <11% and never greater than 23%. (B) Comparison of K-12 strain M182 and EHEC strain O157:H7. Circles represent nonvirulent K-12 strain M182; squares represent pathogenic E. coli O157:H7. Filled symbols represent dsrA+ strains; open symbols represent dsrA mutant strains. Representative data are shown from at least three independent trials; all trials gave similar trends, but with sufficient variability that the data were not superimposable.