Unpacking the black box: How convergent prokaryotic features can inform hypotheses regarding eukaryogenesis
Eijnatten, Bram van
MetadataShow full item record
The term eukaryote refers to organisms with cells that contain a nucleus. This is a special cellular compartment in which the DNA is stored. Animals, plants, fungi and protists are all eukaryotes. There are two other domains of life that do not correspond to nucleated cells. These are the bacteria and archeae, collectively referred to as prokaryotes. Current research indicates that eukaryotes have evolved from a merger between an archeum and a bacterium during a long process called eukaryogenesis. Eukaryotic cells are quite complex compared to prokaryotic cells. Apart from the nucleus they also universally contain many other features that are largely absent from prokaryotic cells. An example is the endomembrane system, which is a set of membranes and cellular compartments that collectively transport and process the molecular components of the cell. How exactly eukaryogenesis took place is still a mystery because all eukaryotic cells have descended from a single ancestor and all intermediate forms of life have gone extinct. This makes it difficult to determine the order in which different cellular features evolved, and the evolutionary pressures that caused them to evolve. Sometimes a prokaryotic species harbors a feature that is very similar to a eukaryotic feature. We can, by comparing the two, use these prokaryotic features to learn about the process of eukaryogenesis. Often these prokaryotes have only one such feature which allows scientists to study it in isolation, rather than in a complex eukaryotic cell. A complex endomembrane, for instance, also occurs in the bacterium G. obscuriglobus. In this literature thesis we show many examples of cellular features that occur in a prokaryote and are very similar to a eukaryotic feature. We than show how these parallel features can be used to form hypotheses about the process of eukaryogenesis. There is a great diversity of prokaryotic organisms on the planet. Only an incredibly small fraction of these has been investigated under the microscope. It is likely that in future work many additional complex features will be discovered in prokaryotes. Our approach will therefore only become more relevant with time.