Section: New Results

A novel view on reductive evolution

Participants: G. Beslon, C. Knibbe, B. Batut

Bacterial genomes show substantial variations in size. The smallest bacterial genomes are those of endocellular symbionts of eukaryotic hosts, which have undergone massive genome reduction and show patterns that are consistent with the degenerative processes that are predicted to occur in species with small effective population sizes. However, similar genome reduction is found in some free-living marine cyanobacteria that are characterized by extremely large populations. Using a combination of bioinformatics approaches and of in silico experimental evolution (with the aevol model), we have been able to propose a scenario that explains the reductive evolution of marine bacteria.

This work was part of Bérénice Batut's PhD thesis [10] , which was defended in November 2014. Bérénice was co-supervised by Guillaume Beslon and Carole Knibbe (Inria Beagle team) for the simulations and by Gabriel Marais and Vincent Daubin (Laboratoire de Biométrie et Biologie Evolutive, UMR CNRS 5558) for the genomic analyses. This work had already yielded a publication in 2013 [34] . This year, we published a review in the high-level journal [11] . The scenario proposed in the PhD manuscript, as well as the simulations and analyses done this year to support it, should be published in 2015.