Interactions between cells and mobile elements such as viruses and plasmids (the mobilome) have played a major role in life evolution. However, up to now, evolutionary studies have mainly focused on cellular genomes (building species trees). My project is to reconstruct the history of interaction between cells, plasmids and viruses (PVs) at the domain level to answer questions such as: to which extent PVs co-evolved with their hosts? How was cellular history influenced by PVs? What is the main directionality of gene fluxes between PVs and cells? The project will focus on Archaea, the third domains of life, because we only have a robust species phylogeny for this domain. We will perform an exhaustive description of PV families in all available archaeal genomes, as well as free PVs, using a combination of in silico methods and expert analyses. Phylogenetic and network analyses will be used to reconstruct the history of PVs with the objective to quantify horizontal versus vertical evolution and to sort out the web and tree-like components of archaeal history. Preliminary analyses have revealed the importance of horizontal gene transfer (HGT) in archaeal evolution. However, the processes behind these HGT remain mysterious, especially for hyperthermophiles. In parallel to our in silico analyses, we will explore the possible role of membrane vesicles (MV) in HGT. We have shown that archaeal MVs can transfer DNA and that some of them harbour plasmid or viral genomes. We want tackle questions such as: can these MVs transfer DNA between different species, different orders or even different domains? We will also study MV formation and fusion in comparison to those involved in viral infection to better understand possible evolutionary and physiological connections between MV and PV. Production of MV is a universal process and their role in life evolution could have been largely underestimated up to now.