Mining Archaea-Bacteria inter-domain symbioses to decipher eukaryogenesis – ABiSYM

Recent advances in environmental microbiology, metagenomics and phylogenomics strongly suggest that the eukaryotic cell evolved from symbiotic consortia involving one member of the Asgard archaea and, at least, the alphaproteobacterial ancestor of the mitochondrion. However, many genes of prokaryotic origin in the last common eukaryotic ancestor were neither archaeal nor alphaproteobacterial. To ascertain their origin, it is essential to better understand the microbial ecology of symbiotic consortia involving Asgard archaea to know with whom they interact in natural ecosystems. In this project, we will combine metagenomic, single-cell, microscopy and cultivation approaches to identify members of Asgard syntrophic consortia in redox transition environments and characterize their metabolic interactions. Through the study of favored partner lineages in these consortia and the bacterial lineages co-existing with Asgard archaea in the same environment, we hope to identify putative bacterial gene donors to Asgard ancestors of eukaryotes. All this information might help us refining current models on eukaryogenesis.