Mitochondrial origins

Abstract

The 16S ribosomal RNA sequences from Agrobacterium tumefaciens and Pseudomonas testosteroni have been determined to further delimit the origin of the endosymbiont that gave rise to the mitochondrion. These two prokaryotes represent the α and β subdivisions, respectively, of the so-called purple bacteria. The endosymbiont that gave rise to the mitochondrion belonged to the α subdivision, a group that also contains the rhizobacteria, the agrobacteria, and the rickettsias - all prokaryotes that have developed intracellular or other close relationships with eukaryotic cells.