The Non-Flagellar Type III Secretion System Evolved from the Bacterial Flagellum and Diversified into Host-Cell Adapted Systems
(A) Representation of the three possible scenarios for the relative emergence of the flagellum and of the NF-T3SS. The numbers represent the percentage of each scenario in the bootstrap analysis of the ATPase family (out of 997 bootstrap trees where outgroup sequences were monophyletic, Figure S2, Protocol S1, Text S1). (B) The maximum likelihood tree of the ATPase family shows that the NF-T3SS derives from the flagellum. Support values are shown only for relationships important to discriminate between the three scenarios in the panel (A). They correspond to the occurrence of the splits in 1000 bootstrap replicates. The multiple alignment used to build this tree had 296 informative sites and is supplied in Dataset S1.