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