Marseillevirus, heterotrimeric nucleosome, molecular model. The image shows the DNA strands in dark red and tan and the four histone doublets in green, orange, blue and purple. Marseillevirus is a genus of viruses in the family Marseilleviridae. There are currently only two species in this genus, including the type species Marseillevirus marseillevirus, from which the nucleosome was taken.