THERE’S A BUG IN TNE OINTMENT. “On the basis of phylogenetic studies, part of these bacterial genes can be readily attributed to the alphaproteobacterial endosymbiont from which mitochondria evolved. Yet, the origin of the remaining set of bacterial genes in eukaryotic genomes, which seemingly lacks phylogenetic coherence, is a matter of debate.”
http://www.biochemsoctrans.org/content/41/1/451.full