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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 ]
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]
The tiny (0.6 μm) marine cyanobacterium Prochlorococcus, discovered in 1986, forms today an important part of the base of the ocean food chain and accounts for much of the photosynthesis of the open ocean [84] and an estimated 20% of the oxygen in the Earth's atmosphere. [85]
Viruses are found wherever there is life and have probably existed since living cells first evolved. [106] The origin of viruses is unclear because they do not form fossils, so molecular techniques have been used to compare the DNA or RNA of viruses and are a useful means of investigating how they arise. [107]
Virosphere (virus diversity, virus world, global virosphere) was coined to refer to all those places in which viruses are found or which are affected by viruses. [1] [2] However, more recently virosphere has also been used to refer to the pool of viruses that occurs in all hosts and all environments, [3] as well as viruses associated with specific types of hosts (prokaryotic virosphere, [4 ...
The viral DNA is then replicated inside the nucleus by the host cell's machinery. Virus particles are assembled in the cytoplasm, usually occupying a space near the inner face of the nucleus. Due to the extremely small size of the algae cells, the average burst size was found to be 25 virus particles per cell. [45]
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]