Clustering of the sequences of putative TonB-dependent transporters (TBDTs). The sequences found by the described genome-wide searches were analysed by CLANs as depicted. (A) shows the consensus tree of the pair-wise mean cluster distances. The branches are coloured according to their respective bootstrap value in shades of grey as indicated by the legend in the middle of the tree. The numbers at each leaf are of the format 'x_y', where 'x' is the cluster number and 'y' the number of sequences belonging to this cluster. We have further indicated the transported substrates and the regions as shown in Figure 1B are marked by I to XII and A to N. Brackets indicate that the metal ion is known, but the metallophore has not yet been identified. An asterisk marks predicted substrates. (B) shows the result of two-dimensional clustering in CLANS. The regions from Figure 1A are marked by red polygons (containing at least a single exp/pTBDT) and red circles (no functionally characterized TBDT). Sequences with a high similarity (P-value < 10-90) are connected by lines coloured in shades of grey (the darker the smaller the P-value). The regions shown in Figure 2 (grey dashed line) and Figure 3 (grey dashed-dotted line) are highlighted.