However, they are able to grow in amoebae infected by Mimiviridae of any of the groups A, B, and C.[3] Sputnik was first isolated in 2008 from a sample obtained from humans; it was harvested from the contact lens fluid of an individual with keratitis.

[4] Naturally however, the Sputnik virophage has been found to multiply inside species of the opportunistically pathogenic protozoan Acanthamoeba, but only if that amoeba is infected with the large mamavirus.

The mimivirus is a giant in the viral world; it has more genes than many bacteria and performs functions that normally occur only in cellular organisms.

It has been observed that when Mimivirus is cultured with germ-free amoeba, bald virions are produced that lack the surface fibers that are characteristic of this virus.

For reasons unknown, Sputnik is unable to replicate and produce new virions in these bald viruses.

In one of the experiments done by inoculating Acanthamoeba polyphaga with water containing an original strain of APMV, it was discovered that several capsid layers accumulate asymmetrically on one side of the viral particle causing the virus to become ineffective.

Sputnik decreased the yield of infective viral particle by 70% and also reduced the amoeba lysis by threefold at 24h.

[2] Sputnik has a circular double stranded DNA genome consisting of 18,343 base pairs.

[9] Several other homologues such as those of a helicase-primase, a packaging ATPase, an insertion sequence transposase DNA-binding subunit, and a Zn-ribbon protein, were detected in the Global Ocean Survey environmental data set, suggesting that virophages could be a currently unknown family of viruses.