Recent developments on bacterial evolution into eukaryotic cells

Abstract

This article stems from the presentation of Mauro Degli Esposti at the 19th Meeting of Evolutionary Biology held in Marseille and summarizes recent developments that have emerged in regard to the evolution of the eukaryotic cell. After updating the application of recently introduced approaches for evaluating the likely bacterial relatives to the symbionts that originated the mitochondrial organelles, the article examines the possibility that such symbionts might have engaged in a syntrophic association with ammonia-oxidizing archaea. The bacterial ancestors of mitochondria could have provided the ammonia required for chemoautotrophic growth of the archaean host, the nitrite by-product of which could have been subsequently recycled back to ammonia by the pathway of nitrate assimilation that is shared by a few proteobacteria and several eukaryotes. The similarity of this syntrophic association with the symbiosis between nitrogen-fixing bacteria and plants is discussed in detail. The article then explores the possible presence of relics of archaean lipids in current eukaryotes, a fundamental problem that weakens current views on the evolution of the eukaryotic cell.