Figure 2.

Neighbor-joining tree of SctC (outer membrane secretin) homologs in Burkholderia and selected Gram-negative plant and animal specific pathogens and symbionts. Accession numbers and source organisms are indicated on leaves. Significant bootstrap values are shown above branches. Components of B. pseudomallei type III secretion systems (T3SS clusters 1–3) are marked in bold letters. Hrp1: Family of T3SS known from plant pathogens including Ralstonia solanacearum and Xanthomonas campestris. Hrp2: Family of T3SSs found in plant pathogens like Pseudomonas syringae and Erwinia species. Animal path: T3SSs from human/animal symbionts and pathogens.