Genome size reduction through multiple events of gene disintegration in Buchnera APS

The evolution of the endosymbiont Buchnera during its adaptation to intrace llular life involved a massive reduction in its genome. By comparing the or thologous genes of Buchnera, Escherichia coli and Vibrio cholerae, we show that the minimal genome size of Buchnera arose from multiple events of gene disintegration dispersed over the whole genome. The elimination of the gen es was a continuous process that began with gene inactivation and progresse d until the DNA corresponding to the pseudogenes were completely deleted.