Inactivation of bacteriophage MS2 with potassium ferrate(VI)

Abstract - Ferrate [Fe(VI); FeO42-] is an emerging oxidizing agent capable of controlling chemical and microbial water contaminants. Here, inactivation of MS2 coliphage by Fe(VI) was examined. The inactivation kinetics observed in individual batch experiments was well described by a Chick-Watson model with first-order dependences on disinfectant and infective phage concentrations. The inactivation rate constant ki at a Fe(VI) dose of 1.23 mgFe/L (pH 7.0, 25oC) was 2.27(±0.05) L/(mgFe×min), corresponding to 99.99% inactivation at a Ct of ~4 (mgFe×min)/L. Measured ki values were found to increase with increasing applied Fe(VI) dose (0.56-2.24 mgFe/L), increasing temperature (5-30C), and decreasing pH conditions (pH 6-11). The Fe(VI) dose effect suggested that an unidentified Fe by-product also contributed to inactivation. Temperature dependence was characterized by an activation energy of 39(±6) kJ mol-1, and ki increased >50-fold when pH decreased from 11 to 6. The pH effect was quantitatively described by parallel reactions with HFeO4- and FeO42-. Mass spectrometry and qRT-PCR analyses demonstrated that both capsid protein and genome damage that increased with the extent of inactivation, suggesting that both may contribute to phage inactivation. Capsid protein damage, localized in the two regions containing oxidant-sensitive cysteine residues, and protein cleavage in one of the two regions may facilitate genome damage by increasing Fe(VI) access to the interior of the virion