Phylogenetic tree of the RND transporters AcrB, AcrF, AcrD, CusA, MdtF, MdtB, and MdtC fromE. coliMG1655 and AcrB, AcrD, MdtB, MdtC, MdtV and MdtW fromE. amylovoraEa1189. Multiple sequence alignment was performed using Clustal Omega [28] and the result visualized by FigTree [29].