EFFECT OF OZONE ON METABOLIC-ACTIVITIES OF ESCHERICHIA-COLI K-12

Escherichia coli K-12 cell suspensions in buffer were exposed to ozone at a concentration of 600 ppm. Measurements were made of cell viabili ty, glyceraldehyde-3-phosphate dehydrogenase, malate dehydrogenase, la ctate dehydrogenase, glutathione disulfide reductase, nonprotein sulfh ydryl and total sulfhydryl compounds. Cell viability was not affected when E. coli K-12 was exposed to ozone for less than 10 minutes. The m ost sensitive parameter was glyceraldehyde-3-phosphate dehydrogenase f ollowed by nonprotein sulfhydryl and total sulfhydryl compounds. Effec ts on malate dehydrogenase, lactate dehydrogenase and glutathione disu lfide reductase were negligible. Cell survival and induction of lipid oxidation were also determined using two strains of E. coli K-12 (rec A, deficient in DNA repair and wild-type). The extent of membrane lipi d oxidation correlated with cell viability in a dose-dependent manner and the survival curves of both strains showed similar sensitivity to ozone. The data suggest that the sulfhydryl group in the membrane is t he primary target of ozone attack. Rec A DNA repair system does not ap pear to play a role in ozone resistance. Copyright (C) 1997 Elsevier S cience Ireland Ltd.