Comparison of UV-Induced Inactivation and RNA Damage in MS2 Phage across the Germicidal UV Spectrum

Abstract

c Polychromatic UV irradiation is a common method of pathogen inactivation in the water treatment industry. To improve its disinfection efficacy, more information on the mechanisms of UV inactivation on microorganisms at wavelengths throughout the germicidal UV spectrum, particularly at below 240 nm, is necessary. This work examined UV inactivation of bacteriophage MS2, a common surrogate for enteric pathogens, as a function of wavelength. The bacteriophage was exposed to monochromatic UV irradiation from a tunable laser at wavelengths of between 210 nm and 290 nm. To evaluate the mechanisms of UV inactivation throughout this wavelength range, RT-qPCR (reverse transcription-quantitative PCR) was performed to measure genomic damage for comparison with genomic damage at 253.7 nm. The results indicate that the rates of RNA damage closely mirror the loss of viral infectivity across the germicidal UV spectrum. This demonstrates that genomic damage is the dominant cause of MS2 inactivation from exposure to germicidal UV irradiation. These findings contrast those for adenovirus, for which MS2 is used as a viral surrogate for validating polychromatic UV reactors. UV irradiation is a common method of disinfection in the water treatment industry. UV light induces damage to the genomes of bacteria, protozoa, and viruses, breaking bonds and forming photodimeric lesions in nucleic acids, DNA, and RNA (1, 2). These lesions prevent both transcription and replication and ultimately lead to inactivation of the microorganisms (3, 4). Direct UV damage to nucleic acids occurs at the wavelengths absorbed by DNA and RNA, in the germicidal UV region between 200 and 300 nm (5, 6). In this wavelength range, however, UV light also damages other cellular and viral components, causing, for example, photochemical reactions in proteins and enzymes (7,8). For this reason, UV sources that emit polychromatic light, across the germicidal UV spectrum, are considered more effective at inactivating certain pathogens than sources that emit monochromatic light at 253.7 nm (9-12). As polychromatic sources become more common, more research is being undertaken to understand the mechanisms of inactivation occurring in pathogens exposed to polychromatic UV irradiation.Male-specific (MS2) coliphage is a single-stranded RNA virus. It infects strains of Escherichia coli that produce F ϩ pili, which serve as viral receptors. The virion consists of a short singlestranded RNA genome (3,569 bases) surrounded by an icosahedral protein capsid, 27 nm in diameter (13). MS2 is commonly used in the water treatment industry as a surrogate for enteroviruses because of its similar size, shape, and genome composition (9,14). It serves as a biodosimeter for UV disinfection studies (15) and for UV reactor validation in North America (14, 16). For reactor validation, MS2 is also used as a surrogate for Cryptosporidium and adenovirus, despite the differences in UV sensitivity and spectral sensitivity between these microorganisms. Recent interest has grown regarding microbial ...

Dual UV irradiation-based metal oxide nanoparticles for enhanced antimicrobial activity in <em>Escherichia coli</em> and M13 bacteriophage

“…Each spectrum of UV-A and UV-C is a powerful disinfection tool. 5,15,22 UV-C has a germicidal peak at 253 nm and is generally used for disinfection. UV-A also has disinfection potential against harmful insects.…”

“…1,2 Under UV irradiation, they also target microorganisms and enhance the antimicrobial activities as disinfection agents in a purification system. 4,5 Thus, the combination of UV and MO nanoparticles can be applied for a future disinfection system. [9][10][11] Adsorption function of MO nanoparticles to microorganisms can induce the disruption of bio-membranes and massive leakage of cell contents, due to their surface characteristics and physicochemical properties.…”

“…23,24 They have antimicrobial activities against various bacteria and viruses, such as Streptococcus aureus (Gram-positive), E. coli (Gram-negative), and MS2 bacteriophages, 5,25,26 and even antibiotic-resistant bacteria 1,27 due to their adsorption to biomembrane and photocatalytic functions. They possibly enhance adsorption potential in terms of interaction with membrane components such as proteins, lipids, and peptides.…”

UV-LEDs Efficiently Inactivate DNA and RNA Coliphages

“…Doses from 41 to 60 mWs/cm 2 were needed to reach 2-3 Log 10 -reductions of MS2 at wavelengths of 255-280 nm (excluding 270 nm) [13,18,24], while approximately 110 mWs/cm 2 was needed at 285 nm to reach 3 Log 10 -reduction [21]. However, a tunable laser at 270 nm has yielded 1.5 and at least 3 Log 10 -reductions of MS2 with doses of 20-30 mWs/cm 2 and 60 mWs/cm 2 , respectively [33,34]. The tunable laser at a lower wavelength of 253.7 nm yielded approximately 3.5 Log 10 -reduction of MS2 with a dose of 70 mWs/cm 2 [33], which corresponds to our result.…”

“…Nucleotides have UV absorbance peaks between 240 and 280 nm and absorption maximum of DNA is considered to be near 260 nm [36]. UV-absorption of proteins generally peaks at 280 nm [37] although proteins of some viruses may efficiently be affected by wavelengths below 240 nm [33,34]. In addition, wavelengths on UVA region (above 315 nm) may produce reactive intermediates and oxidative damage to DNA and other components of the bacterial cell [38,39].…”