The results were comparable to those of the analyses of the complete protein sequences. Similarly, comparing only the C-termini, AIDA-I clusters in one phylogenetic

branch with AatA, thus the C-terminus of AatA seems to be most related to that of AIDA-I (Figure 3B). The amino acid residue alignment of the C-termini of AIDA-I and AatA revealed a number of identical residues as shown in Figure 3C. Comparing only the C-terminus one has to keep in mind that this part contains the transmembrane domain to span the bacterial membrane, thus it is likely to be the most conserved part among all autotransporter adhesins. Figure 3 see more Phylogenetic tree of autotransporter adhesins including AatA. The phylogenetic trees were calculated with the Neighbor-Joining-Algorithm Antiinfection Compound Library cost on the basis of a ClustalW multiple alignment of 24 protein sequences from known adhesins of the autotransporter family including AatA. The percentages of replicate trees in which the associated taxa clustered together in the bootstrap test (1000 replicates) are shown next to the branches. Protein sequences were obtained from the NCBI database. A: Phylogenetic tree (NJ-tree) obtained using the complete 24 protein sequences. B: NJ-tree obtained using only the last 256 amino acid residues according to the smallest protein HadA

in ClustalW analyses. Here, only proteins clustering in one phylogenetic branch with AatA are shown. C: The amino acid residue PtdIns(3,4)P2 alignment of the C-termini of AIDA-I and AatA are shown highlighting identical residues (*indicates fully conserved residues, :indicates fully conserved strong groups, .indicates fully conserved weaker groups). Symbols indicate the species: *Escherichia coli, # Neisseria meningitidis, °Haemophilus influenzae, + Yersinia enterocolitica, ‘Moraxella catarrhalis, ´´Helicobacter pylori, $ Xylella fastidiosa, **Salmonella Typhimurium, and & Bordetella pertussis. We also examined the amino acid differences of the conserved AatA proteins in E. coli IMT5155, APEC_O1 and BL21 and B_REL606, respectively. The AatA of the latter two strains are 100% identical. In

total, 19 amino acid substitutions were found in the C-terminus containing the transmembrane domain; 3 variable positions lie within the passenger domain and 13 differences in amino acid sequence were found in the N-termini of the AatA proteins (Figure 4). Interestingly, the transmembrane domains of BL21 and IMT5155 are 100% identical and the 19 C-terminal amino acid differences occur in APEC_O1 compared to these two strains. Also the majority of amino acid substitutions within the N-terminus (10 of 13) occur in APEC_O1 in contrast to the almost identical AatA proteins from BL21 and IMT5155 (only 3 substitutions). Taken together, the adhesins of the two APEC strains differ more than the AatA proteins of IMT5155 and the non-pathogenic BL21 strain.