Editing Parasitism (section)

=== Viruses ===

{{main|Virus |Bacteriophage}}

[[Virus]]es are obligate intracellular parasites, characterised by extremely limited biological function, to the point where, while they are evidently able to infect all other organisms from bacteria and [[archaea]] to animals, plants and fungi, it is unclear whether they can themselves be described as living. They can be either [[Orthornavirae|RNA]] or [[DNA virus]]es consisting of a single or double strand of [[genetic material]] ([[RNA]] or [[DNA]], respectively), covered in a [[protein]] coat and sometimes a [[lipid]] envelope. They thus lack all the usual machinery of the [[cell (biology)|cell]] such as [[enzyme]]s, relying entirely on the host cell's ability to replicate DNA and synthesise proteins. Most viruses are [[bacteriophage]]s, infecting bacteria.<ref name=Koonin2006>{{cite journal |last1=Koonin |first1=E. V. |last2=Senkevich |first2=T. G. |author3=Dolja, V. V. |title=The ancient Virus World and evolution of cells |journal=Biology Direct |volume=1 |page=29 |year=2006 |pmid=16984643 |pmc=1594570 |doi=10.1186/1745-6150-1-29 |doi-access=free }}</ref><ref name="Breitbart M, Rohwer F 2005 278–84">{{cite journal|author-link1=Mya Breitbart |author1=Breitbart, M. |author2=Rohwer, F. |title=Here a virus, there a virus, everywhere the same virus? |journal=Trends in Microbiology |volume=13 |issue=6 |pages=278–284 |year=2005 |pmid=15936660 |doi=10.1016/j.tim.2005.04.003}}</ref><ref name="Lawrence">{{cite journal|author1=Lawrence, C. M. |author2=Menon, S. |author3=Eilers, B. J. |display-authors=etal |title=Structural and functional studies of archaeal viruses |journal=The Journal of Biological Chemistry |volume=284 |issue=19 |pages=12599–603 |year=2009 |pmid=19158076 |doi=10.1074/jbc.R800078200 |pmc=2675988|doi-access=free }}</ref><ref>{{cite journal |last1=Edwards |first1=R. A. |last2=Rohwer |first2=F. |url=https://www.cbcb.umd.edu/confcour/CMSC828G-materials/Edwards-Rohwer-2005-NatureReviewsMicro.pdf |archive-url=https://web.archive.org/web/20191003133000/https://www.cbcb.umd.edu/confcour/CMSC828G-materials/Edwards-Rohwer-2005-NatureReviewsMicro.pdf |archive-date=3 October 2019 |url-status=live |title=Viral metagenomics |journal=Nature Reviews Microbiology |volume=3 |issue=6 |pages=504–510 |year=2005 |pmid=15886693 |doi=10.1038/nrmicro1163|s2cid=8059643 }}</ref>