Hi everyone!

Welcome to #MicroTwJC 55, hosted on 14/10/2014 by @_LisaKWilliams_ and @Stewart_Barker.

This week we will be discussing the fascinating world of virophages – that is viruses which attack other viruses. The paper can be found here: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0094923

Following a previous #MicroTwJC discussion on the largest discovered viruses, this fairly recent paper describes a satellite virus (or virophage) named Zamilon that is associated with the giant virus family Mimiviridae. Zamilon is similar to other described virophages which have negative effects on their host – Sputnik virophages, yet does not appear to inhibit it’s host in any way…


“The host-specificity of the Zamilon virophage supports the distinction between satellite viruses (opportunistic entities associated with a virus) and virophages, which target specific hosts.”


Aside from what we think is an interesting paper and concept, the above quote is a crucial point of the paper. We leave you with the abstract and questions to consider below, and look forward to a lively debate!


Virophages, which are potentially important ecological regulators, have been discovered in association with members of the order Megavirales. Sputnik virophages target the Mimiviridae, Mavirus was identified with the Cafeteria roenbergensis virus, and virophage genomes reconstructed by metagenomic analyses may be associated with the Phycodnaviridae. Despite the fact that the Sputnik virophages were isolated with viruses belonging to group A of theMimiviridae, they can grow in amoebae infected by Mimiviridae from groups A, B or C. In this study we describe Zamilon, the first virophage isolated with a member of group C of theMimiviridae family. By co-culturing amoebae with purified Zamilon, we found that the virophage is able to multiply with members of groups B and C of the Mimiviridae family but not with viruses from group A. Zamilon has a 17,276 bp DNA genome that potentially encodes 20 genes. Most of these genes are closely related to genes from the Sputnik virophage, yet two are more related to Megavirus chiliensis genes, a group B Mimiviridae, and one to Moumouvirus monve transpoviron.


Points to consider

  1. Is the paper well written?
  2. Do the methods fully investigate whether the Zamilon virophage has a disruptive effect on its host?
  3. Are the results and discussion appropriate?
  4. Is Zamilon a virophage, or a satellite virus? Is there actually a difference between the two terms?