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Marine viruses are defined by their habitat as viruses that are found in marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. Viruses are small infectious agents that can only replicate inside the living cells of a host organism , because they need the replication machinery of the host to ...
The origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids—pieces of DNA that can move between cells—while others may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer , which increases genetic diversity . [ 32 ]
The cell achieves its height in the water column by synthesising gas vesicles. As the cell rises up, it is able to increase its carbohydrate load through increased photosynthesis. Too high and the cell will suffer photobleaching and possible death, however, the carbohydrate produced during photosynthesis increases the cell's density, causing it ...
The viruses cannot move independently and must rely on currents, mixing, and host cells to transport them. Viruses cannot actively target their hosts and must wait to encounter them. The higher probability of collision may explain why cyanophages of the Myoviridae family primarily infect one of the most abundant cyanobacteria, Synechoccocus. [3]
Some members of this family can have a linear double-stranded DNA while others have a circular double stranded DNA. The genome has been found to be up to 560 kilobases in length. Up to 50% of the DNA can be represented by guanine or cytosine. This virus is known to infect algae, which means it is found in the ocean. [26]
[3] [4] There has been little research on mixotrophic protists, but recent studies in marine environments found mixotrophic protists contribute a significant part of the protist biomass. [5] Since protists are eukaryotes (and not prokaryotes) they possess within their cell at least one nucleus, as well as organelles such as mitochondria and ...
The linear size of the average virus is about one one-hundredth that of the average bacterium. Most viruses cannot be seen with an optical microscope so electron microscopes are used instead. [105] Viruses are found wherever there is life and have probably existed since living cells first evolved. [106]
Evidence has been found, however, to indicate that viruses found in vent habitats have adopted a more mutualistic than parasitic evolutionary strategy in order to survive the extreme and volatile environment in which they exist. [32] Deep-sea hydrothermal vents were found to have large numbers of viruses, indicating high viral production. [33]