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Because known stress response pathways were activated in L. plantarum WCFS1 during growth in the presence of ethanol, we examined whether this strain could withstand higher levels of other chemical or environmental stresses after exposure to ethanol compared to normally grown cells. The cross-protective stress tolerance levels of L. plantarum cultures grown for 24 h in the presence of ethanol were determined by exposing the cells to lethal levels of hydrogen peroxide (40 mM), UV radiation (254 nm, ranging from 0 to 180 s), acid pH (pH 2.4), and elevated temperatures (37°C to 53°C), as well as growth in high NaCl concentrations (0.6, 0.7, and 0.85 M).