Endosymbiosis in doubt

Researchers have provided compelling evidence to discount one of the mainstream views in biology regarding the evolution of eukaryotic cell structure. Eukaryotic cells are those which make up virtually all complex, multicellular life on Earth. They are markedly different from that of prokaryotes (bacteria and archaea); they have a cell nucleus that contains DNA as well as mitochondria and other structures. Bacteria and archaea on the other hand merely have free-floating DNA within the cell membrane. One mainstream theory in biology suggested that the structures in eukaryotes originated as disparate organisms eventually forming a symbiotic relationship, called endosymbiosis.

Temple Smith and Hyman Hartman, from Boston University and MIT respectively, conducted research on a particular structure found in many eukaryotic cells called cilia. Cilia are hairlike projections from a cell which help move and sense the environment. These are one of many structures believed to be originated from endosymbiosis. However, Smith and Hartman, through newly available genomic techniques, were able to determine that genes responsible for the cilia have a uniqueness that could not be present in the simple organisms believed to be part of the endosymbiosis. Therefore, it is suggested that the cilia must have arisen from within via evolutionary forces not yet understood.

While this research can only speak with regard to cilia alone, the notion can be easily extrapolated for the many other structures in eukaryotic cells as well, casting much doubt over the notion of endosymbiosis.














(image shows electron micrograph scan of cilia in human trachea)