The extensive genome reduction that is observed in bacterial endosymbionts is expected for species with small effective population sizes; however, similar reduction is observed in some free-living marine cyanobacteria that have extremely large effective population sizes. In this Opinion article, the authors discuss the different hypotheses that have been proposed to account for this reductive genome evolution at both ends of the bacterial population size spectrum.
- Bérénice Batut
- Carole Knibbe
- Vincent Daubin