Mimivirus.  The huge regular icosahedral capsid contains lipid membranes and other structures	T-even phage particle: note elongated isometric head (icosahedron with hexamer expansion net), helical tail, and base plate and neck structures	Depiction of a orthopoxvirus virion.  Note presence of two lipid bilayers and amorphous structure
Link to Wikipedia	Link to Wikipedia	copyright Russell Kightley

Most bacteriophages - or more properly, archaeal and bacterial viruses - have a more complex structure than the simple isometric and helical nucleocapsids typical of many plant and animal viruses.  Even viruses with relatively small genomes may have more than one type of architecture associated with their virions, normally in the shape of some kind of TAIL structure attached to an isometric HEAD.  The T-even viruses - part of the "T4-like virus" genus, family Myoviridae - have the general structure shown centre, above: this is an isometric head attached via a connector assembly to a contractile helically-constructed tail with a rigid core, with tail fibres and baseplate.  See here for explanation of how the virus gains entry to enterobacterial cells.

λ-like viruses - family Siphoviridae - have thinner non-contractile tails and isometric heads, with tail fibres.   The P22-like and Φ29-like viruses in family Podoviridae and Salmonella phage Epsilon 15 have isometric heads and short, thick tails. 

 

Enterobacteria phage λ	Enterobacteria phage P22	Bacillus phage Φ29	Salmonella phage Epsilon 15
copyright Russell Kightley			Reprinted by permission from Macmillan Publishers Ltd: Jiang W, et al.  Nature. 2006 Feb 2;439(7076):612-6 copyright 2006

 

	Tutorial Contents
"What is a Virus?"	Helical Nucleocapsids	Isometric Virions	Enveloped Virions