Acid challenge of S. Enteritidis cpxR and dps deletion mutants. Wild type S. Enteritidis, S. Enteritidis ΔcpxR, S. Enteritidis Δdps, and both genetically complemented mutants were challenged to a highly acidic environment following PA adaptation. Unadapted and PA adapted cultures were challenged for one hour in LB broth (pH 3.0). Acid resistance was determined by calculating the overall percent survival of each culture following acid exposure. Presented data is the average of three independent trials. Standard error is represented by error bars. Acid resistant phenotypes that differ significantly from the unadapted condition are indicated with an asterisk.