A study led by Thijs Ettema (Uppsala University/SciLifeLab) indicates that mitochondria evolved from a completely different type of proteobacteria than previously suggested. The results are published in Nature.
For many years it has been proposed that mitochondria, organelles with a central role in both cellular energy production and apoptosis, originate from an aerobic alphaproteobacteria that managed to survive the engulfment by a eukaryotic cell. Through becoming incorporated into its cytoplasm, the bacteria would provide a survival benefit for the eukaryote as an oxygen-dependent metabolic system became available. However, researchers have not managed to identify this proposed ancestor.
By analyzing large amounts of environmental sequencing data from the Pacific and the Atlantic Ocean, the research team behind the present study has successfully identified several previously unknown alphaproteobacterial groups. Using newly developed methods, they then reconstructed the genomes of over 40 alphaproteobacteria, belonging to 12 different groups.
Unexpectedly, the data points to mitochondria not being the closest relatives to any of these alphaproteobacterial groups. Rather, the mitochondria seem to have evolved from an ancestor that later gave rise to all currently recognized Alphaproteobacteria.
Read the full paper in Nature