Symbiotic interactions at the origin of eukaryotes

Recent advances in environmental microbiology, metagenomics and phylogenomics strongly suggest that the eukaryotic cell evolved from symbiotic consortia involving an Asgard archaeon and, at least, the alphaproteobacterial ancestor of the mitochondrion.

However, many genes of prokaryotic origin in the last eukaryotic common ancestor (LECA) appear to originate neither from archaea nor alphaproteobacteria, suggesting that other bacteria (e.g. Deltaproteobacteria) may have contributed to eukaryogenesis as additional symbionts or gene donors.

To ascertain the origin of these genes, it is essential to better understand the ecology of symbiotic microbial consortia involving Asgard archaea (AA), and in particular, to identify the partners with which they interact in natural ecosystems.

In this project, I will combine metagenomics, phylogenomics, fluorescence-activated single-cell/consortium sorting, high-throughput microfluidics, state-of-the-art fluorescence and electron microscopy techniques and cultivation approaches to identify and characterize members of AA syntrophic consortia and their associated viruses in a broad variety of microbial mats and oxygen-poor environments.

With this information, I aim to i) identify the partners of AA syntrophic consortia across ecosystems, determine whether they co-evolve and unravel their ecological preferences; ii) characterize the metabolic interactions and phenotypic properties of AA symbiotic consortia in culture and/or from sorted consortia populations; iii) characterize the cell ultrastructure and potential presence of endomembranes in members of AA consortia, their three-dimensional organization and their spatial distribution in microbial mats; and iv) identify potential bacterial symbiotic partners involved in eukaryogenesis, in addition to the mitochondrial alphaproteobacterial ancestor, and/or gene donors to the LECA or its Asgard archaeal ancestor.

Our results should substantially advance understanding of eukaryogenesis.