Viruses manipulate the marine environment

Marine viruses are affecting all living species and organisms within the marine environment; they have also been shown through much study that they have the ability to change another species ontogeny and life history. Previous virology study has concentrated mostly on two areas, pathogenic impact and also the virus ability to influence the food webs. Viruses have severe impacts on conservation, various pathogens are known to cause great problems in different species, an example given by this paper was sea-turtle fibropapillomatosis and shrimp white spot syndrome, these two diseases have two different impacts in this area, one being fish sustainability with in the shrimp farming industry and the other the sea turtles of which some species are known to be registered on the endangered species act.

Advances in virology have allowed our scientific knowledge to grow considerably and learn how viruses work; this paper concentrates on the marine system. Improved methodology over the past 10-15 years, science has bloomed from the investigation of viral and protist contribution to plankton to RNA virome sequencing. With the measurement of viral diversity problems occur due the culturing difficulties and their lack of the more common universally conserved genes. Through other techniques such as the mentioned shot gun sequencing it was possible to show that scientists have underestimated population and diversity and due to these new effects that viruses have on other species its seen that these have a significant impact on the host adaptation.

The paper explains how the viruses are able to manipulate genes and modify marine organism’s ontogeny. Until recently papers have speculated mainly on the negative effects of the host modification of the virus, but many of these modifications are known to have very positive effects i.e. the cyanobacteria “Synechococcus” which through the horizontal transfer of genes associated with the Ps(II) system it allows the functionality of photosynthesis that is a necessity for the function and existence of this bacteria.

It is suggested that ecological niches of various species in nature are made possible by phage populations found there and it is these that act as a “gene reservoir”, by this it means the ability for many different viruses to carry different many different genes that are exchanged to the hosts and exploited through adaptation. The psB A  gene used to encode the ps(II) co-reactions are passed on through gene transfer from host to host originally seen to be passed on by horizontal transfer from phage and its estimated that roughly  10% of this transfer is responsible for total global photosynthesis. One of the most incredible effects is also carried out by transformation, where by the common known cholera bacterium Vibrio cholerae,  by  incorporating the CTX gene becomes a disease highly dangerous to humanity,  and is even able to gain the ability to be anti biotic resistant.

Viromes are used regularly for particular hosts to acquire various genes used for specific adaptations, high abundance of genes found in high pressure environments such as hydrothermal vents are found to be used by microbial communities  adapting and evolving to capitalise and maintain life in  that difficult environment. It is thought that around 10²⁴ genes a year are transferred  through transduction, but by studying the  GTA’s numbers could be much higher as these phage types have smaller DNA and these only transfer host DNA to the bacterium, which appears to be a highly efficient system.

Several viruses have now been found to be able to move genetic material and information from not just a one organism to another but from one environment to a completely unrelated environment, so..... could total world wide diversity, marine and terrestrial, be limited or allowed expansion by the global movement of virions?

With the discovery of the Mimivirus, some of the largest viruses known to man, study was carried out to see if transfer was greater due to size, it would seem that even though bigger with 1.2 megabases and genetically more complex, horizontal transfer is less common than in the previously spoken about phage. A study was conducted in Plymouth looking at a particular species of coccolithophorid Emiliania huxleyi, this species is known to go through a boom or bust cycle whereby they bloom at an astonishing rate and then vanish. This was thought to be caused by a specific virus associated with E.huxleyi , using satellite imagery looking for cell reflection it was seen that the area was low in this species of coccoliths but high in the associated virus and free coccoliths suggesting that the E.huxleyi went through lysis caused by infection of the virus. To conclude this experiment, two coccolithovirus were isolated and the genome sequenced from these showed to be a 400kb marine viral genome known to contain the genes capable of ceramide production.

What I find particularly interesting in this paper is the ability of certain species such as the E.huxleyi  even though they display resistance to this virus, the virus its self manages to adapt to these changes known as “The Red Queen” hypothesis. But even though these viral adaptations to the resistance the coccolith occur,  the host manages to perform what has been coined “The Cheshire Cat” whereby it utilises two life stages in order to avoid the virus all together and “disappear”.

It amazes me how in the last 15 or so years with increase of technology we have seen how viruses once thought to have purely negative impacts on nearly all ecosystems, have been proven not just to have advantageous impacts  but imperative for the increase and depth of the global gene pool, the ability for species to mingle genetically and benefit from each other in many ways. Also for species to still manage to find ways in order adapt, to the fight of flight mechanism of dealing with the harmful pathogens.

To read this paper further please see below.

Rohwer, Forest, and Rebecca Vega Thurber. "Viruses manipulate the marine environment." Nature 459.7244 (2009): 207-212.