RESPONSE OF PSEUDOMONAS-AERUGINOSA PAO FOLLOWING EXPOSURE TO HYDROGEN-PEROXIDE

Hydrogen peroxide (H2O2) is used in various applications to prevent, c ontrol, or decrease bacterial activity in e.g. cooling water, hospital s, recreational waters and the food industry. The aim of the work repo rted here was to investigate the response of P. aeruginosa following e xposure to H2O2 during both logarithmic and stationary phases of growt h. The catalase levels were determined following exposure to H2O2, and the general cellular response was investigated by pulse-labelling usi ng S-35 methionine. Stationary phase cells did not demonstrate a stres s response to H2O2. Where de novo protein synthesis was inhibited, cel ls were less susceptible to growth inhibition, indicating an inverse s tress response to H2O2 in P. aeruginosa. The addition of H2O2 to cultu res in logarithmic growth phase resulted in the induction of a short l ag phase. The growth rate following a return to logarithmic growth pha se was lower than before addition of H2O2, and was inversely related t o the concentration of H2O2 added. Oxidising stress elicited de novo s ynthesis of four proteins within 5 min following exposures to stress. Cellular catalase levels doubled from 16 U . mg(-1) protein to over 30 U . mg(-1) protein within 10 min following exposure to oxidising stre ss but no new catalase isozymes were induced. H2O2 was demonstrated to interrupt cell division as well as to decrease the ensuing rate of di vision in P. aeruginosa, and the culture did not exhibit an effective stress response to H2O2.