There are plenty of grisly things in the natural world, and the universe of microbes is no different. But for some reason the life cycle of megaviruses disturbs me as much as any blood-sucking, brain-invading metazoan parasites known to science:

The unusual size and gene content of the virus led one scientist to suggest that viruses could explain the origin of DNA-based life. If viruses carried all these genes, then it’s possible to imagine that one could set up shop in a cell and simply never leave … A paper is being released today, however, that argues that this scenario has things exactly backwards. Giant viruses, its authors argue, have all these genes normally associated with cells because, in their distant evolutionary past, they were once cells.