Engineering yeast endosymbionts as a step toward the evolution of mitochondria

Abstract

It has been hypothesized that mitochondria evolved from a bacterial ancestor that initially became established in a protoeukaryotic cell as an endosymbiont. Here we model this first stage of mitochondrial evolution by engineering endosymbiosis between E. coli and the budding yeast S. cerevisiae. Fusion of yeast with E. coli ectopically expressing several genes from unrelated, intracellular bacteria was key for establishing endosymbiosis. ADP/ATP translocase‐expressing E. coli provided an energy source for a respiration‐deficient cox2 yeast mutant, enabling growth of yeast‐E. coli chimera on a non‐fermentable carbon source. Similarly, yeast provided a source of thiamin or NAD to an E. coli thiamin or NAD auxotroph respectively. Expression of several SNARE‐like protein on the surface of E. coli was also required to prevent lysosomal degradation. The engineered yeast‐E. coli chimeras sustained growth on selection medium in containing the antibiotic carbenicillin indicating the presence of intracellular E. coli which supports the growth by ATP synthesis on selection medium. Further, sf‐gfp expressing E. coli endosymbionts could be observed in the yeast by super resolution fluorescence microscopy after more than 40 doublings. This readily manipulated system should allow us to experimentally delineate host‐endosymbiont adaptations that occurred during evolution of the current much reduced mitochondrial genome This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Endosymbiosis before eukaryotes: mitochondrial establishment in protoeukaryotes

“…Whether the organelle could be reintroduced into these hosts by the artificial integration of a new bacterial partner remains to be seen in the lab. There are already cutting-edge experiments with genetically engineered symbionts: an auxotrophic, ANT-expressing E. coli was successfully integrated within a respiration-devoid yeast where the bacterium can export ATP while depending on host's thiamine [170]. Similar tools can be employed to engineer endosymbioses with immediate purloined benefits for the host and dependence benefits for symbiont, due to auxotrophy.…”

Synthetic Biology Tools to Engineer Microbial Communities for Biotechnology

“…These randomly introduced auxotrophies can be used to develop yeast communities that enter a state of syntrophic metabolic cooperation [37]. Co-auxotrophic interactions have also been engineered between a respiration-deficient yeast (via deletion of cox2 , a mitochondrial gene encoding a subunit of cytochrome c oxidase) and endosymbiotic E. coli [38]. Here, the yeast provides thiamin to an E. coli auxotrophic for this vitamin and the E. coli shares ATP with the yeast host.…”

Meet the relatives of our cellular ancestor

“…In any case, the many models for the origin of eukaryotes 5,11,14,15 highlight the importance of initial syntrophic associations 5,14,15 and membrane-mediated processes 10,11 . Interestingly, albeit for different reasons, both syntrophy and membranes were crucial aspects in an engineered synthetic relationship in which an Escherichia coli bacterium was maintained inside a yeast cell for more than 120 days 16 .…”