Viruses as regulators of nutrient cycles in aquatic environments (original) (raw)
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Marine Ecology Progress Series, 2003
The possible influence of viral infection on respiration rates in marine microbial pelagic communities was assessed by means of 3 experiments on respiration rate with viral concentrate addition on single-species cultures of Mantoniella sp. and Micromonas pusilla and another 3 on natural microplankton communities (organisms < 200 µm) from the Kattegat Sea (Åstol) and the Baltic Sea. Coastal surface seawater samples were taken during cruises of the RVs 'Ancylus' and 'Argos' during winter and spring 2000. Approximately 50 to 70 l of seawater were concentrated by ultrafiltration. The experiments were started by adding a viral particle concentrate to a container with algae or a natural microplankton community; a control container was kept free of the viral concentrate addition. Oxygen concentration determinations were carried out on each treatment and control to measure respiration rates throughout the incubation period. The in vivo chlorophyll a fluorescence was also monitored as an indication of algal infection. The rates of respiration indicated that the addition of the viral particle concentrate affected the respective metabolisms of the Mantoniella sp. and Micromonas pusilla cultures as well as natural microplankton communities. Viral infection decreased the Mantoniella sp. respiration rate (by 96%) and increased the Micromonas pusilla respiration rate (by 235%). Hence, if our results can be extrapolated to nature, then, at least in a bloom situation, the fate of primary production and carbon fluxes could be strongly modulated by viral infection. The addition of a viral particle concentrate to the microplankton community generated complex responses in terms of respiration rates, which increased (by 84%) or remained similar to the controls. Our results suggest that viral infection of microplanktonic organisms could be one of the factors significantly modifying pelagic carbon fluxes.
The Plymouth Student Scientist, 2009
Phytoplankton is the main driver of ocean net primary production (Falkowski et al., 1998) and a dominant force behind biogeochemical cycling in the ocean. It is a component of one of the oldest and best described virus-host relationships (e.g. Suttle et al., 1990). Viruses have typically been viewed as pathogens of marine organisms but it has become clear that they also play a critical role in biogeochemical processes in marine systems, themselves falling into the category of dissolved organic matter (DOM) (Wilhelm & Suttle, 1999). Viruses play a large part in carbon (Middelboe & Lyck, 2002), sulphur (Hill et al., 1998) and iron cycling (Poorvin et al., 2004) in the world‟s oceans. Earth‟s climate has warmed by approximately 0.6°C during the last 100 years. The rate of warming has doubled in the second half of the century (Houghton, 2001). This rapid change has been attributed to the impact of anthropogenic activities on the atmosphere. Climate change is already affecting marine eco...
The ISME journal, 2015
Viral lysis of microbial hosts releases organic matter that can then be assimilated by nontargeted microorganisms. Quantitative estimates of virus-mediated recycling of carbon in marine waters, first established in the late 1990s, were originally extrapolated from marine host and virus densities, host carbon content and inferred viral lysis rates. Yet, these estimates did not explicitly incorporate the cascade of complex feedbacks associated with virus-mediated lysis. To evaluate the role of viruses in shaping community structure and ecosystem functioning, we extend dynamic multitrophic ecosystem models to include a virus component, specifically parameterized for processes taking place in the ocean euphotic zone. Crucially, we are able to solve this model analytically, facilitating evaluation of model behavior under many alternative parameterizations. Analyses reveal that the addition of a virus component promotes the emergence of complex communities. In addition, biomass partitioni...
Effects of Viruses on Nutrient Turnover and Growth Efficiency of Noninfected Marine Bacterioplankton
2000
TheeffectsofvirusinfectionandlysisofamarineVibriosp.onC,N,andPturnoverandthegrowthefficiency of noninfected bacterioplankton were studied in a series of dilution cultures. The cultures were enriched with various sources of organic matter and N and P. The growth of theVibriohost and the growth of the natural bacterioplanktonweremeasuredbyimmunofluorescenceand4*,6-diamidino-2-phenylindolestainingmethods, respectively. Lysis products resulting from infection of theVibriosp. caused an increase in metabolic activity and cell production by the noninfected bacterioplankton. In P-limited
The elemental composition of virus particles: implications for marine biogeochemical cycles
Nature Reviews Microbiology, 2014
| In marine environments, virus-mediated lysis of host cells leads to the release of cellular carbon and nutrients and is hypothesized to be a major driver of carbon recycling on a global scale. However, efforts to characterize the effects of viruses on nutrient cycles have overlooked the geochemical potential of the virus particles themselves, particularly with respect to their phosphorus content. In this Analysis article, we use a biophysical scaling model of intact virus particles that has been validated using sequence and structural information to quantify differences in the elemental stoichiometry of marine viruses compared with their microbial hosts. By extrapolating particle-scale estimates to the ecosystem scale, we propose that, under certain circumstances, marine virus populations could make an important contribution to the reservoir and cycling of oceanic phosphorus.
Metabolic and biogeochemical consequences of viral infection in aquatic ecosystems
Nature Reviews Microbiology, 2019
Ecosystems are controlled by 'bottom-up' (resources) and 'top-down' (predation) forces. Viral infection is now recognized as a ubiquitous top-down control of microbial growth across ecosystems but, at the same time, cell death by viral predation influences, and is influenced by , resource availability. In this Review , we discuss recent advances in understanding the biogeochemical impact of viruses, focusing on how metabolic reprogramming of host cells during lytic viral infection alters the flow of energy and nutrients in aquatic ecosystems. Our synthesis revealed several emerging themes. First, viral infection transforms host metabolism, in part through virus-encoded metabolic genes; the functions performed by these genes appear to alleviate energetic and biosynthetic bottlenecks to viral production. Second, viral infection depends on the physiological state of the host cell and on environmental conditions, which are challenging to replicate in the laboratory. Last, metabolic reprogramming of infected cells and viral lysis alter nutrient cycling and carbon export in the oceans, although the net impacts remain uncertain. This Review highlights the need for understanding viral infection dynamics in realistic physiological and environmental contexts to better predict their biogeochemical consequences.
Virus-driven nitrogen cycling enhances phytoplankton growth
2012
ABSTRACT: Viruses have been implicated as major players in aquatic nutrient cycling, yet few data exist to quantify their significance. To determine the effect of viruses on ammonium regeneration by bacteria, experiments were carried out in the oligotrophic Indian Ocean and productive False Creek, Vancouver, Canada. Bacteria were concentrated and then diluted with virus-free water to reduce virus abundance, or with virus-replete water to restore natural virus abundances.