A context for Chlorella Viruses: Size

Chlorella viruses are big.  Consider the titles of the following review papers dealing with them:

The Phycodnaviridae: The Story of How Tiny Giants Rule the World

DNA Viruses: The Really Big Ones (Giruses)

Structures of giant icosahedral eukaryotic dsDNA viruses

There are two aspects to the size of a virus: the size of the actual virus (called the virus particle) and the length of its genome.  Chlorella Viruses have an enormous genome, but it’s been forever since I was immersed in any scientific literature, so what do I know?  To give myself a sense of perspective, I graphed it with some other virusgenomes (shown below).  Note that I scaled everything up to the HIV-1 genome being 1 inch, so everything here is relative to that.  Why 1 inch?  Why not.

Virus genome size

Viruses shown (increasing genome lengths): HIV-1 clone HXB2, Measles Virus, Hu Adenovirus type 2, Epstein Barr Virus, Cowpox Virus, Hu Cytomegalovirus, Paramecium Bursaria Chlorella Virus FR483, Ectocarpus Siliculosis Virus, Paramecium Bursaria Chlorella Virus NY2A, Emiliana Huxeyli Virs 86, Phaeocystis Globosa Virus, Bacillus Megatherium Phage G, Cotesia Congregata Bracovirus, Mimivirus, Pandoravirus

Don’t read anything into the progression of genome lengths from left to right; I placed these viruses somewhat randomly, so there is no meaning there other than increasing genome length.

So Chlorella Viruses have some big genomes.  Not the biggest, but big.

You might find your brain assuming that virus particle in which that genome is packaged would be bigger too.  I found my mind creeping that way too until I made myself look up the data and produced the graph below.

Virus particle size

There are some fascinating observations here, the first being that some viruses have quite a large range of sizes while others are quite tight.  So while a type 2 human Adenovirus is always about 90nm across, HIV-1 can actually range from 80nm to 180nm across.  Part of the range for some of thse has to do with whether the size ranges I found (as noted at the end, some of these are from Swiss Institute for Bioinformatics, while others are from review articles) are for different “species” of virus within the same Genus or different sizes produced by a singly infected cell (both types of variation exist for many viruses).  Measles Virus is the surprise for me here.  Its genome length is somewhere between HIV-1 and Adenovirus, but look at how big the range of sizes produced (that is from a single study using one virus/host cell combination).  Didn’t know that.

So Chlorella Virus’s genome is big, but the actual virus itself is not all that big.

Sources

Genomes:

 For Epstein Barr Virus, Cowpox Virus,  Paramecium Bursaria Chlorella Virus FR483, Ectocarpus Siliculosis Virus, Paramecium Bursaria Chlorella Virus NY2A, Emiliana Huxeyli Virs 86, Phaeocystis Globosa Virus, Bacillus Megatherium Phage G, Cotesia Congregata Bracovirus, Mimivirus, Pandoravirus: http://www.giantvirus.org/top.html and Swiss Institute for Bioinformatics

For human: GenBank GRCh37.p13 6/28/2013

For mouse: Mouse Genome Consoritum (Nature. 2002 Dec 5;420(6915):520-62.)

For marbled lungfish: http://www.genomesize.com/statistics.php

For onion: I don’t remember, but go check it, this is legit.

About SubOptimist

I am an Assistant Professor in the Science Department at Georgia Perimeter College, Newton. I teach introductory biology courses at both the majors and non-majors level in addition to microbiology. Previous to that I spent 7 years as a postdoctoral researcher on different viruses. While I don't miss being on the "grant treadmill", I think better when I write and miss writing up data for papers and grants; this blog helps me with that a little. And sometimes my kids' insanely funny and cute antics need to be shared with the world. Any view expressed in this blog is that of me personally and not Georgia Perimeter College or the GPC Newton Science Department.
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