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-inhibi tory activity of HOCl and H2O2 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 inhib itory concentrations (MIC) were determined during the ensuing 24 h. Th e effect of oxidant on logarithmically growing cultures was also deter mined. Stationary phase cultures of E. coli K12 responded to H2O2 stre ss, both the MIC and survival following exposure to high concentration s increasing following exposure to stress. By contrast stationary phas e cells did not become more tolerant of high concentrations of HOCl fo llowing HOCl stress. Logarithmically growing E. coli K12 did not displ ay increased tolerance to either inhibitory or lethal concentrations o f H2O2 or HOCl following the relevant oxidising stress.