Viral dynamics: a model of the effects of size shape, motion and abundance of single-celled olanktonic organisms and other particles

Abstract

The transport of aquatic viruses to particles can be described in terms of diffusive transport from solution. Such transport is influenced by motion of the water relative to the particle. Because transport rate is determined purely by physical factors it is independent of whether the particle is a host or non-host organism. The low viral diffusivity relative to that for dissolved nutrients makes transport enhancement from organism swimming more important for viruses. The virus contact rate with bacteria is relatively unaffected by such motions because of small bacterial sizes. Transport rates for phytoplankton and protozoa can increase over an order of magnitude when swimming motions are considered. Although larger organisms have much higher transport rates per individual, their far lower concentrations In sea water should make small organisms the preferred targets for viruses. Rates of host-virus interactions in culture are closely related to predictions from transport theory. There is a fairly close relationship between bacterial populations and virus disappearance rates in the marine environment, suggesting that non-host organisms are a major cause of viral mortality at the higher ionic strengths typical of sea water. Other factors, such as UV radiation, must also be included when estimating viral mortality in seacvater.

Re-examination of the relationship between marine virus and microbial cell abundances

“…Virus propagation requires contacting and infecting cells. The per cell rate at which microbial cells -including bacteria, archaea, and microeukaryotes -are contacted by viruses is assumed to be proportional to the product of virus and microbial abundances [33]. If virus and microbe [12], ZoBell [59] 1947…”

Bridging the Gap between Knowing and Modeling Viruses in Marine Systems—An Upcoming Frontier

“…Model kept evolving in complexity and detail ever since (e.g., Pasquer et al, 2005;Libralato and Solidoro, 2009;Ramin et al, 2012;Hasumi and Nagata, 2014), but viruses have been mostly kept out of this evolution in the algorithms. Some models, however, have addressed the dynamic of viruses with considerable detail, but not in a full ecological modeling framework (Angly et al, 2006), by tackling the specific virus-host relationship (Ruardij et al, 2005) having as a start point previous modeling approaches of virus-host relationships (Murray and Jackson, 1992). Viral-induced lysis was eventually included in complex marine models with the parameterization of phytoplankton cell lysis largely based on empirical findings.…”

“…However, the static nature of the model prevented its use in the study of dynamic ecosystems and to properly describe the very dynamic process of viral growth. At the same time, Murray and Jackson (1992) advanced a detailed model for the relationship between viruses and planktonic organisms, modeling the lysis of hosts proportional to the density of both host and viruses (as a type-I functional response). So, while lacking a specific component to account for viral activity, and missing some of the viruses-mediated processes that have been discovered more recently, early attempts to model viruses dynamics paved the way for more complex biogeochemical models that had essential components for the inclusion of virus (e.g., the microbial loop).…”

“…Still, viruses are sometimes neglected (e.g., Follows and Dutkiewicz, 2010;Salihoglu et al, 2013), and only a few attempts have been made to model the details of bacterial and phytoplankton viral-induced cell lysis. Early modeling approaches have incorporated viral infection in simple models (Murray and Jackson, 1992), but not on biogeochemical models accounting for the fate of the DOM produced in the process, for example. Model kept evolving in complexity and detail ever since (e.g., Pasquer et al, 2005;Libralato and Solidoro, 2009;Ramin et al, 2012;Hasumi and Nagata, 2014), but viruses have been mostly kept out of this evolution in the algorithms.…”

Dynamic modelling of viral impact on cyanobacterial populations in shallow lakes: implications of burst size

“…where U¼population density of uninfected cells, V¼population density of free virions, c¼host^virus contact rate expressed as a volume clearance rate per particle (see Murray & Jackson, 1992), s 1 ¼fraction of virions adsorbed upon contact with host cell, s 2 ¼fraction of infective virions. Cells are not only infected but also removed by their lysis when the lytic cycle is completed:…”