Assessment of UV-B damage in cyanophage PP

Abstract

Cyanophage PP is a short-tailed, icosahedral-shaped, double-stranded DNA virus and can be frequently detected with high abundance and activity in many eutrophic lakes in China. Solar radiation is one of the main factors affecting cyanophage infectivity. In this study, cyanophage PP was treated with different intensities of UV-B radiation, and the accumulation of cyclobutane pyrimidine dimers (CPDs), viral particle destruction and viral attachment ability were analyzed. The viral infectivity decay rate under white and red light was also studied using plaque-forming assays. The results indicate that (1) the level of CPDs induced by UV-B was significantly correlated with radiation intensity, while exposure dose had little effect on the DNA damage level, (2) the level of CPDs was significantly correlated with both the decay rate and the repair rate in cyanophage PP, and (3) UV-B could result in the destruction of viral particles and the decrease in viral attachment. This work suggests that the secondary and tertiary structure of the DNA may influence the formation of CPDs, and that capsid damage caused by UV-B radiation may play an important role in viral decay and survival.

Bacteriophages: Practical Applications for Nature's Biocontrol

“…UV radiation has been demonstrated to damage cyanophages (Asato 1976), and plays a big role in cyanophage decay. It also plays an important role in the destruction of viral particles and the decrease in viral infectivity and viral attachment to host cells (Suttle and Chen 1992;Liao et al 2010). Their calculations suggested that in clear oceanic waters exposed to full sunlight, most of the virus decay, averaged over a depth of 200 m, would be attributable to solar radiation.…”

“…When decay rates were averaged over 24 h for a 10-m coastal water column, loss rates of infectivity attributable to sunlight were similar to those resulting from all other processes combined. Loss of viral infectivity after exposure to SUR seems to be mainly caused by damage to the viral genome, although indirect damage to the capsid has also been suggested to result in inactivation Liao et al 2010). It was found that UV-B (290-320 nm) and UV-A (320-400 nm) radiation that directly and indirectly damages viral DNA, penetrate to a considerable depth in seawater (Suttle and Chen 1992).…”

Characterization and dynamics of cyanophages from tropical surface waters

“…Environmental factors affect viral absorption, replication, burst size and fate of viruses. The fate of cyanophages has been shown to be influenced by environmental conditions: (1) adsorption rate is affected by light (Kao et al 2005), nutrient (Mann 2006) and host physiological condition (Brussaard 2004); (2) infectivity is affected by temperature (Franche 1987), divalent cations (Mole et al 1997) and pH (Franche 1987); (3) latent period and burst size are affected by light (Adolph and Haselkorn 1972;Kim and Choi 1994) and nutrients (Wilson et al 1996); (4) structural stability and decay rate are affected by temperature (Garza and Suttle 1998;Manage et al 1999), UV (Liao et al 2010), divalent cations (Mole et al 1997), attachment to cells or particles and consumption by protozoa (Suttle 2000a);…”

“…As a result, this is able to maintain high cyanophage concentrations in surface waters (Graze and Suttle, 1998). An assessment of UV-B damage on cyanophage PP (cyanophage infecting Plectonema boryanum and Phormidium foveolarum) conducted by Liao and colleagues (2010), showed that UV-B induced capsid destruction and decreased viral adsorption ability, thus affecting the survival of cyanophages (Liao et al 2010).…”

“…Environmental conditions are know to affect the physiological conditions of cyanobacteria (Mann 2006) and subsequently affect the binding sites of cyanophage to cyanobacteria (Brussaard 2004). In addition, the adsorption rate of cyanophage to cyanobacteria (Kao et al 2005), viral life strategies (including entrance into lysogenic or lytic cycle and latend period of virus) (Danovaro et al 2011), and decay rates (Franche 1987;Liao et al 2010) of cyanophages are also affected by environmental conditions. In-situ studies have been carried out to investigate the temporal and spatial dynamics of cyanophage abundance.…”