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Modeling Cellular Evolution Through Engineered Endosymbiosis

Written by Phyllis Shen

Scientists at the Scripps Research Institute genetically modified and examined two different microorganisms. Scientists have theorized that before DNA, RNA was used as the primary genetic information and that RNA could catalyze biochemical reactions due to its less stable nature compared to DNA. In order for this to be true, there had to have been a transition at some point from RNA to DNA. Escherichia coli bacteria containing both DNA and RNA in its genetic sequence allowed the researchers to study the evolutionary transition from RNA to DNA as the primary genetic material of most organisms. The bacteria were genetically engineered such that they were able to rebuild their own DNA using ribonucleotides rather than deoxyribonucleotides. Ribonucleotides contain a ribose sugar and are found in RNA while deoxyribonucleotides contain deoxyribose sugar and are found in DNA.

In a separate paper on the same study, yeast containing a endosymbiotic bacterium were used by the researchers to study the evolution of eukaryotes through examining the origins of the mitochondria. The yeast and the bacteria exhibited a mutualistic relationship; the yeast relied on the bacteria for cellular energy while the bacteria relied on the yeast for essential nutrients. The researchers inhibited the function of the yeasts’ mitochondria, so any ATP present would be produced by the bacteria. The bacteria within the yeasts contained surface proteins on the membranes, which prevented them from being destroyed by the yeast. The results of this study showed that the bacteria and yeast were able to coexist through mutualism for at least 40 generations. Random mutations caused some bacteria to have a stronger resistance towards degradation within the yeast; these small changes in the gene sequence of the bacteria allowed for the reproduction of the bacteria and inheritance of these adaptations to the next generation.

This research will be continued as the researchers continue to investigate the evolution of organisms that caused DNA to be the main genetic code and the mitochondria to be present within cells to perform cellular respiration. This will be accomplished by genetically engineering E. coli and adding these bacteria to new cells to function as mitochondria. Scientists hope to uncover more information about the evolution of cell structures by genetically engineering microorganisms and closely observing the endosymbiotic relationships between the microorganisms.

Citation for Modeling Cellular Evolution Through Engineered Endosymbiosis: Scripps Research Institute. (2018, October 29). Synthetic microorganisms allow scientists to study ancient evolutionary mysteries: Scientists use the tools of synthetic biology to engineer organisms similar to those thought to have lived billions of years ago. ScienceDaily. Retrieved November 16, 2018 from

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