Ozone is a major component of photochemical smog. High levels of this pollutant, sufficient to affect human health are found in many urban areas worldwide. Though limited studies in humans are supported by extensive findings from animal experiments, a difficulty in interpreting the results of these experiments has lead to an ambiguity on the biochemical mechanism of ozone toxicity. To elucidate the mechanism by which ozone causes cell damage and eventual cell death we conducted a comprehensive study using Escherichia coli K-12 as a model.
Studies on the comparative inactivation of bacteriophage lambda (λ), Escherichia coli, and Candida albicans showed that λ was significantly more sensitive to ozone, in buffered solutions. The quenching effect of antioxidants in body fluids decreased the inactivation rate of λ. Short interval exposure of E. coli K-12 transformed with pACYC184 plasmid DNA resulted in protein and nucleic acid leakage and production of thiobarbituric acid reactive substances, without affecting cell viability. The intracellular components, protein and plasmid DNA, remained intact. The enzymes malate dehydrogenase, lactate dehydrogenase and glutathione disulfide reductase were unaffected, while glyceraldehyde-3-phosphate dehydrogenase activity decreased significantly. Glutathione and total sulfhydryl compounds were also very sensitive to ozone oxidation. With longer duration of ozone exposure cell viability decreased with a more significant increase in lipid oxidation and protein and nucleic acid leakage. The total intracellular proteins and plasmid DNA showed progressive degradation corresponding to the decrease in cell viability.
Cell survival, induction of lipid oxidation and intracellular protein and DNA damage in two strains of E. coli K-12 (recA and wild type) were shown to be equally susceptible to ozone. Rec A protein levels decreased subsequent to ozone exposure indicating that this enzyme is not involved in the DNA repair process after ozone-induced damage. The membrane components are the primary targets of ozone damage with subsequent reactions involving the intracellular components, protein and DNA. The sulfhydryl groups of cytoplasmic components are preferentially oxidized by ozone. E. coli therefore offers a convenient model system for studying short- and long term ozone-induced cellular damage.
Benjamin H. S. Lau
Robert L. Health
James D. Kettering
Brain J. Mudd
Doctor of Philosophy (PhD)
Year Degree Awarded
Date (Title Page)
Library of Congress/MESH Subject Headings
Escherichia coli -- drug effects; Escherichia coli -- cytology; Ozone -- toxicity; Bacteriophage lambda; Candida albicans -- drug effects.
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This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.
Komanapalli, Indira Ruth, "Cellular Responses in ESCHERICHIA COLI to Lethal and Sublethal Doses of Ozone" (1997). Loma Linda University Electronic Theses, Dissertations & Projects. 1477.
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