Influence of previous sub-lethal heat, cold and acid treatments on Escherichia coli BJ4 resistance to (+)-limonene.

a, b, c: same letters indicate non-significant differences among mean values; p>0.05.Log10 of survival counts (CFU/mL) of Escherichia coli BJ4 (wild type) and BJ4L1 (ΔrpoS) (initial concentration: 3·107 CFU/mL) by a treatment with 200 µL/L of (+)-limonene in citrate-phosphate buffer of pH 4.0. Table includes data from non-stressed cells (control) and cells exposed to different sub-lethal shocks before (+)-limonene treatments (mean ± standard error). Sub-lethal heat shock: 45 °C/2 h; sub-lethal cold shock: ice/4.5 h; sub-lethal acid shock: pH 4.5/1 h.