MS2 coliphage viruses suspended in buffered distilled water were rapidly inactivated by < 5 mg/L iodine doses, losing 6 logs (99.9999%) of infectivity within less than 3 min contact time. The effect of pH on MS2 inactivation within the range of 6 to 8 was not statistically significant. However, in the presence of dissolved organic substances, such as detergents and proteins, the inactivation of MS2 viruses decreased significantly to less than 4 logs (99.99%). Of special interest was that in the presence of beef extract proteins, an apparent reversal of MS2 inactivation, dubbed rebound, was observed. It was observed that after an initial 5 to 6 log reduction in infectivity, a consistent and statistically significant increase in the number of plaque forming units (PFU), as much as 2 logs, was measured. MS2 rebound occurred only when the oxidized iodine residual had been quickly consumed by beef extract proteins in solution. Neither virus particle aggregation nor water salinity were found to account for the increase in PFU values. Based on other investigators' suggestions that iodine disinfection caused changes to viral protein coats, it was hypothesized that conformational changes in MS2's protein coat caused by iodine would result in a change in the isoelectric focusing point of whole MS2 virions. A shift in isoelectric focusing point from an acidic pH value of 3.9 to more basic values, and a dispersion of the virus band after exposure to high levels of iodine was observed, supporting the hypothesis that iodine caused changes in the charge distribution characteristics of the protein coat.
|Number of pages||11|
|State||Published - Jan 1999|
Bibliographical noteFunding Information:
This research was a project of the Center for Space Environmental Health which was a NASA Center for Research and Training supported by the Biological Sciences Division of NASA (Grant NAGW 2356). The Center for Space Environmental Health was a joint project of the University of Rochester School of Medicine and the University of Colorado. The authors would like to thank Dr. Mark Sobsey and his laboratory manager Doug Wait of the University of North Carolina, Chapel Hill for help with the viral assay methodology and providing the seed MS2 virus stock. Sandy Dee, a microbiologist with Denver Water Department, provided valuable advice and consultation.
- Iodine disinfection
ASJC Scopus subject areas
- Ecological Modeling
- Water Science and Technology
- Waste Management and Disposal