Mini Microbes
ComaVN writes "According to an article in Nature, a group at the University of Regensburg, Germany has found the smallest lifeform ever. It lives under extremely hostile (to us that is) conditions, in boiling water, and it has a genome of only about half a million DNA letters. Of course, smallest lifeform depends heavily on your definition of life, as most virii are actually smaller. But let's not get into that discussion :p"
It's viruses, not virii. http://language.perl.com/misc/virus.html has a good overview of this argument, or check any dictionary or biology text.