Ecology

Viruses are highly specific to the hosts they can infect and infection is density dependent, consequently viruses exert strong selection pressure over marine ecosystems. Steady sate viral cropping of certain populations has been observed [4] whilst in contrast viruses have also been held responsible for crashes of phytoplankton blooms [5]. A more direct effect on community composition results from the transfer genetic material by viruses [6], which over time could homogenise genes throughout susceptible populations.

Biogeochemistry

Viral lysis converts living cells into dissolved organic matter which then becomes available to bacteria and phytoplankton. This has the net effect of regenerating nutrients and maintaining biomass in the euphotic zone as otherwise matter and energy would be passed to higher trophic levels and lost from the food web via sinking [7]. Viruses may also influence global climate and the sulphur cycle by facilitating the production of dimethyl sulphide (DMS) a climatically active trace gas from marine systems [8].

Current Research

Current research in collaboration with Dr Willie Wilson of the Marine Biological Association aims to determine how marine viruses influence the production of DMS. Previous cultures studies of phytoplankton which contain dimethylsulphoniopropionate (DMSP) the cellular precursor of DMS revealed that viruses cause the total release of DMSP from Micromonas pusilla [9] and viral lysis of nonaxenic cultures of Phaeocystis pouchetii resulted in DMS accumulation in the medium [8].

Using the Emiliania huxleyi host virus system, the relative contributions of grazing, autolysis and viral lysis on sulphur cycling is being determined. Areas of investigation include the partitioning of sulphur compounds during viral lysis, and whether DMS production is quantitatively linked to DMSP lyase activity, the enzyme which coverts DMSP to DMS. Future work will examine the influence of nutritional status and the influence of bacteria on production of DMS and related compounds.

Images

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Bacteria Lysis

E. huxleii V86 culture lysis

Marine Virus

Links

Virology
The Marine Biological Association

References

[1] O. Bergh et al., Nature, vol. 340, pp. 467-468, 1989.
[2] L. M. Proctor and J. A. Fuhrman, Nature, vol, 343, pp. 60-62, 1990.
[3] J. A. Mayer and F. J. R. Taylor, Nature, vol. 281, pp. 299-301, 1979.
[4] M. G. Weinbauer and M. G. Holfe, Applied Environmental Microbiology, vol, 94, pp. 431-438, 1998.
[5] G. Bratbak, Journal of Marine Systems, vol, 9, pp. 75-81, 1996.
[6] H. X. Chiura. Aquatic Microbial Ecology, vol, 13, pp. 75-83, 1997.
[7] J. A. Fuhrman, Nature, vol, 399, pp. 541-548, 1999.
[8] G. Malin et al., Liminology and Oceanography, vol, 43, pp. 1398-1393, 1998.
[9] R. W. Hill et al., Aquatic Microbial Ecology, vol, 14, pp. 1-6, 1998