Figure 5

An evolutionary scenario for the origin and evolution of the archaeal flagellum. Blue, red, orange and purple clusters represent fla 1 cluster, fla 2A cluster, fla 2B cluster and their ancestor, respectively. The black circle represents the last common ancestor of Archaea. The green circle represents the duplication event that led to the fla 1 and fla 2 clusters. This duplication event occurred before the last common ancestor of Archaea, which thus harbored the two types of clusters. The red circle represents the recent duplication event of the fla 2 cluster in ancestor of Methanosarcina. The blue and red crosses represent the loss of the fla 1 and fla 2A clusters, respectively.