The response of Escherichia coli K12 upon exposure to hypochlorous acid and hydrogen peroxide

The aim of the work reported here was to investigate the growth-inhibitory activity of HOCI and hydrogen peroxide toward Escherichia coli K12 during both logarithmic and stationary phases of the growth cycle, as well as the response of E. coli K12 to these oxidants. Stationary phase cultures were exposed to sub-inhibitory oxidising stress, and the minimum inhibitory concentrations (MIC) were determined during the ensuing 24h. The effect of oxidant on logarithmically growing cultures was also determined. Stationary phase cultures of E. coli K12 responded to hydrogen peroxide stress, both the MIC and the survival following exposure to high concentrations increasing following exposure to stress. By contrast stationary phase cells did not become more tolerant of high concentrations of HOCI following HOCI stress. Logarithmically growing E. coli K12 did not display increased tolerance to either inhibitory or lethal concentrations of hydrogen peroxide or HOCI following the relevant oxidising stress