AWWA WQTC58950

AWWA WQTC58950 Comparing Ozone Inactivation of Closely Related Bacillus Species Using the Ct Concept and Atomic Force Microscopy
Conference Proceeding by American Water Works Association, 11/02/2003

Dow, S.M.; Mavrocordatos, D.; Egli, T.; Koester, W.; Hernandez, M.T.; von Gunten, U.

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Inactivation experiments were conducted with Bacillus megaterium spores (B. megaterium, asspores) and Bacillus subtilis spores (B. subtilis, as spores) to investigate the differences in inactivationbehavior among very closely related microorganisms. It was observed that the inactivation behaviorof B. megaterium was very different than that of B. subtilis. B. megaterium did not exhibit a lag phaseas observed with B. subtilis and the kinetics of inactivation were faster for B. megaterium. Inaddition, inactivation of B. megaterium does not appear to be pH dependent while some previouslypublished research indicates a pH dependence of B. subtilis. The inactivation response of thesemicrooganisms was different in Lake Zurich water than it was in oxidant demand free phosphatebuffer. Physical responses of both microorganisms were observed in a flow through cell using AtomicForce Microscopy (AFM), which allowed images to be recovered while ozone inactivation occurred.Oxidative damage to the spore coat could be clearly observed using AFM. The onset of oxidativedamage to the coat of B. subtilis spores occurred markedly later than the onset of oxidative damage toB. megaterium under similar ozone exposure conditions. Includes 16 references, figures.