Megavirales Genetics from Mimivirus to Chilensis
By Adama Berndt
Introduction
The evolutionary history of viruses is an unclear and frequent topic of speculation. Megaviruses are especially unique, as their size and structure are reminiscent of bacterial cells, but their function is similar to that of a classical virus(Abrahao, 2014). Although knowledge of large viruses dates back to the 1970’s, interest in megaviruses expanded during 2003 with the sequencing of Mimivirus; now one of the most well characterized Nucleocytoplasmic Large DNA Viruses(NCLDVs)(Colson, 2012). There are 6 official recognized classes of NCLDVs: Poxviridae, Asfarviridae, Iridoviridae, Ascoviridae, Phycoviridae, Mimiviridae(Colson, 2013; Fig 2.). In addition to these classes Megaviridae is proposed as a seventh class(Yutin and Koonin, 2012). One of the most remarkable recurring traits of these microbes is their large genome size, which at approximately one million base pairs is bigger than some bacterial genomes. These base pairs code for over a thousand genes and this genetic material is surrounded by pseudo-icosahedral protein capsids, similar to a Herpes virus(Legendre, 2012)(Fig. 1.). The taxonomy of viruses as DNA containing microbes has long been considered from many angles. Of special consideration is the status of NCLDVs as living or non-living organisms. From an evolutionary perspective, there are two major sides to this debate, the “virus-early” hypothesis the “virus-late’ hypothesis. The virus-early stance argues that viruses originated before modern cells and the virus-late stance speculates that viruses are the result of a reductive evolution, characterized by an increased benefit from reliance on host metabolism, which propelled the loss of primary cellular machinery. The other potential mechanism of the virus-late camp imagines the escape of proteins and genetic information from cells, that coupled to form viruses(Moreira, 2008). If viruses were formed spontaneously from released cell genetic materials and proteins, me might expect to see some formation of new rudimentary viruses today. The genetic information obtained from Mimivirus has provided extra fuel for speculation in this debate, specifically that Mimivirus contains the first evidence of a virus containing genes for transcription and translation(Raoult, 2007). The full phylogenetic analysis conducted by Raoult and colleagues found several Eukaryotic protein homologues in Mimivirus, and support for Mimivirus as a sister group to Eukaryotes and therefore a new branch of life that would include, Eukaryotes, Prokaryotes, Archaea and Megavirales.
Other examples:
Bold
Italic
Subscript: H2O
Superscript: Fe3+
Introduce the topic of your paper. What is your research question? What experiments have addressed your question? Applications for medicine and/or environment?
A citation code consists of a hyperlinked reference within "ref" begin and end codes.
[1]
Introduction
Include some current research, with at least one figure showing data.
Every point of information REQUIRES CITATION using the citation tool shown above.
Section 2
Include some current research, with at least one figure showing data.
Section 3
Include some current research, with at least one figure showing data.
Section 4
Conclusion
References
- ↑ [http://www.karger.com/Article/Fulltext/336562 Colson, Phillipe. Lamballerie, Xavier de. Fournous, Ghislain. Raoult, Didier. Reclassification of Giant Viruses Composing a Fourth Domain of Life in the New Order Megavirales ." Intervirology 2012;55:321-332. DOI: 10.1159]
Authored for BIOL 238 Microbiology, taught by Joan Slonczewski, 2016, Kenyon College.
