Endosymbioses and Evolution

There is a lot to be gained from attempting to divorce oneself from the past while looking forward at cell biological problems with modern data, and there is clearly much about the evolution of the eukaryotic cell that still needs to be worked out [1].

Scientific definition of the symbiosisThe term “symbiosis”, firstly defined as “the living together of unlike organisms”, is in fact broadly applied to all the spectrum of beneficial, neutral, or harmful relationships [2].

Symbioses include intracellular bacteria in eukaryotic hosts (the core knowledge of ENDOBIOS), which remain largely unseen due to the lack of clear phenotypes and tractable experimental systems [3-6].

Fast facts on bacteria:

  • It is estimated that 99% of all bacterial species are unculturable, a paradigm known as the great plate count anomaly [7], much related to genome reduction with lack of genes essential for free-living [8].
  • With a global diversity estimated between 100 million to 10 billion species [9], bacteria have an outstanding genetic diversity spread throughout 92 Phyla, with more than half of them remaining without a single culturable representative [10].
  • Unculturable bacteria represent a current major challenge in microbiology [9]. Access to the still neglected bacteria that reside on humans (for example our gut microbiota) and discovering their functionalities is expected to provide new ways to improve health [7].


  1. Archibald, John M., Endosymbiosis and Eukaryotic Cell Evolution. Current Biology 2015, 25, (19), R911-R921.
  2. de Bary, A., Die Erscheinung der Symbiose: Vortrag gehalten auf der Versammlung Deutscher Naturforscher und Aerzte zu Cassel. Trübner: 1879.
  3. Lackner, G.; Partida-Martinez, L. P.; Hertweck, C., Endofungal bacteria as producers of mycotoxins. TIMI Trends in Microbiology 2009, 17, (12), 570-576.
  4. Kobayashi, D. Y.; Crouch, J. A., Bacterial/Fungal interactions: from pathogens to mutualistic endosymbionts. Annual review of phytopathology 2009, 47, 63-82.
  5. Tarkka, M. T.; Sarniguet, A.; Frey-Klett, P., Inter-kingdom encounters: recent advances in molecular bacterium-fungus interactions. Current genetics 2009, 55, (3), 233-43.
  6. Rohm, B.; Scherlach, K.; Mobius, N.; Partida-Martinez, L. P.; Hertweck, C., Toxin production by bacterial endosymbionts of a Rhizopus microsporus strain used for tempe/sufu processing. International journal of food microbiology 2010, 136, (3), 368-71.
  7. Harwani, D., The Great Plate Count Anomaly and the Unculturable Bacteria. Int J Sci Res, 2013, 2, (9), 350-351.
  8. McCutcheon, J. P.; Moran, N. A., Extreme genome reduction in symbiotic bacteria. Nature reviews. Microbiology 2011, 10, (1), 13-26.
  9. Overmann, J.; Abt, B.; Sikorski, J., Present and Future of Culturing Bacteria. Annual Review of Microbiology 2017, 71, (1), 711-730.
  10. Hug, L. A.; Baker, B. J.; Anantharaman, K.; Brown, C. T.; Probst, A. J.; Castelle, C. J.; Butterfield, C. N.; Hernsdorf, A. W.; Amano, Y.; Ise, K.; Suzuki, Y.; Dudek, N.; Relman, D. A.; Finstad, K. M.; Amundson, R.; Thomas, B. C.; Banfield, J. F., A new view of the tree of life. Nature Microbiology 2016, 1, 16048.