The role of sunlight in the removal and repair of viruses in the sea

Abstract

We investigated the in situ destruction rates of marine viral particles as well as the decay rates of infectivity for viral isolates along an -400&n transect from oligotrophic offshore waters to productive coastal waters in the Gulf of Mexico. Light-mediated decay rates of viral infectivity averaged over the solar day ranged from 0.7 to 0.85 h ' in surface waters at all stations and decreased with depth in proportion to the attenuation of UVB (305 nm). The destruction rates of viral particles also decreased with depth, although the rates of particle destruction were only 22-61% of infectivity when integrated over the mixed layer. The rates of viral particle destruction indicated that at three of four stations 6-12% of the daily bacterial production would have to be lysed in order to maintain ambient viral concentrations. At the fourth station, where there was a dense bloom of Synechococcus spp. and the mixed layer was shallower, 34-52% of the daily bacterial production would have to be lysed. A comparison of the difference between destruction rates of viral particles and infectivity integrated over the depth of the mixed layer implies that host-mediated repair must have restored infectivity to 39-78% of the sunlight-damaged viruses daily. The calculated frequency of contacts between viral particles and bacterial cells that resulted in infection (contact success) ranged from -18 to 34% in offshore waters, where the frequency of contacts between viruses and bacteria was much lower, to -1.0% at the most inshore station, where contact rates are much higher. This suggests that in offshore waters bacterial communities are less diverse, and that there is less selection to be resistant to viral infection. This paper provides a framework for balancing viral production, destruction, and light-dependent repair in aquatic viral communities.Viruses are ubiquitous and abundant in marine environments, where they infect bacteria, phytoplankton, and heterotrophic flagellates (see reviews by Fuhrman and Suttle 1993; Borsheim 1993;Bratbak et al. 1994). Estimates of viral-induced mortality of marine bacteria range from a small percentage of production to rates that imply that viruses are a major mechanism of bacterial mortality in aquatic systems

Dynamics and diversity of newly produced virioplankton in the North Sea

“…Lytic viruses replicate more rapidly within hosts growing in eutrophic than in oligotrophic waters, that is, in faster growing cells (Hewson et al, 2001). A positive correlation between viral and bacterial turnover time was reported for oligotrophic and mesotrophic environments (Steward et al, 1992;Wilhelm et al, 1998;Noble and Fuhrman, 2000;Hwang and Cho, 2002), whereas no such relation was found in our study.…”

“…This implies explicitly, however, that the main target phylotype for viral infection varies over time and that only a fraction of the viral community is infecting hosts at high rates at any given time. Considering that the richness of bacteriophages in coastal surface waters is relatively high (Wommack et al, 1999b) and that the decay of viruses in surface waters is in the range of 1-2 days (Heldal and Bratbak, 1991;Wilhelm et al, 1998), a rapid succession of infection targets can be assumed and consequently, a tight control of bacterioplankton evenness by bacteriophages. These temporal dynamics in viral infection and phage production have been addressed only on short-time scales (Bettarel et al, 2002;Winter et al, 2004) but viral diversity was not analyzed thus far and is subject of this study.…”

High control of bacterial production by viruses in a eutrophic oxbow lake

“…The specific CRs presented in this study, ranging from 91 to 230 cell , and Lake Erie, with 4 to 11 cell -1 d -1 (Wilhelm et al 1998b, Wilhelm & Smith 2000. Only CRs of Lake Plußsee were close to those of the Alte Donau, varying from 49 to 180 contacts cell -1 d -1 at different depths (Weinbauer & Höfle 1998b).…”

Spatial and temporal dynamics of virioplankton in a high mountain tropical reservoir, El Neusa (Cundinamarca, Colombia)

“…of potential hosts, as well as transformations inflicted on the organic substances that serve as substrates for some of these microorganisms (Visser et al, 1999;Fernández-Zenoff et al, 2006;Ruiz-González et al, 2013). Certain studies suggest that the degree of infectivity and phage production tends to decrease with the increasing of exposure time and the received amount of UV-B radiation (Jeffrey et al, 1996;Noble & Fuhrman, 1997;Weinbauer et al, 1997;Wilhelm et al, 1998Wilhelm et al, , 2003Cheng et al, 2007). For the study area, a time series of monthly average solar radiation from 1960 to 1999 indicates that higher average levels occur commonly between January and March (548-607 cal cm -2 ; CAR, 2005).…”