*nlm.life
			PubMed Journals: Microbiol Mol Biol Rev

  Source:		PMID: 26378223


    		Microbiol Mol Biol Rev. 2015 Dec;79(4):403-18.
     		doi: 10.1128/MMBR.00017-15.

			Cell Walls and the Convergent Evolution
			of the Viral Envelope.

			Buchmann JP(1), Holmes EC(2).

			Author Information
			(1) Marie Bashir Institute for Infectious
			Diseases and Biosecurity, Charles Perkins
			Centre, School of Biological Sciences, and
			Sydney Medical School, The University of Sydney,
			Sydney, New South Wales, Australia.
			(2) Marie Bashir Institute for Infectious
			Diseases and Biosecurity, Charles Perkins
			Centre, School of Biological Sciences, and
			Sydney Medical School, The University of
			Sydney, Sydney, New South Wales, Australia
			edward.holmes@sydney.edu.au.

			Why some viruses are enveloped while others
			lack an outer lipid bilayer is a major question
			in viral evolution but one that has received
			relatively little attention. The viral envelope
			serves several functions, including protecting
			the RNA or DNA molecule(s), evading recognition
			by the immune system, and facilitating virus
			entry. Despite these commonalities, viral
			envelopes come in a wide variety of shapes
			and configurations. The evolution of the viral envelope
			is made more puzzling by the fact that nonenveloped
			viruses are able to infect a diverse range
			of hosts across the tree of life. We reviewed
			the entry, transmission, and exit pathways
			of all (101) viral families on the 2013
			International Committee on Taxonomy of Viruses
			(ICTV) list. By doing this, we revealed
			a strong association between the lack of
			a viral envelope and the presence of a cell
			wall in the hosts these viruses infect.
			We were able to propose a new hypothesis
			for the existence of enveloped and nonenveloped
			viruses, in which the latter represent an
			adaptation to cells surrounded by a cell
			wall, while the former are an adaptation
			to animal cells where cell walls are absent.
			In particular, cell walls inhibit viral
			entry and exit, as well as viral transport
			within an organism, all of which are critical
			waypoints for successful infection and spread.
			Finally, we discuss how this new model for
			the origin of the viral envelope impacts
			our overall understanding of virus evolution.

			Copyright © 2015, American Society for Microbiology.
			All Rights Reserved.

			DOI: 10.1128/MMBR.00017-15 PMCID: PMC4651029
			PMID: 26378223 [Indexed for MEDLINE]

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