Reductive genome evolution at both ends of bacterial population size spectrum
Résumé
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 consistent with degenerative processes 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. Here, we discuss the various hypotheses that have been put forward to account for this reductive genome evolution at both ends of the spectrum of bacterial population size.