The motif logos show the variation of amino acids that have been identified among the 1259 strains. Each logo consists of stacks of symbols, one stack for each position in the sequence. The overall height of the stack indicates the sequence conservation at that position while the height of symbols within the stack indicates the relative frequency of each amino acid at that position. The width of the stack is proportional to the fraction of valid symbols in that position. In order to simplify the motifs present, a single letter code was assigned to each of them (K,A,E,Q,T,G,S,N,V and P). Each strain has a combination of the above motifs, which usually start with K, Q or E. Only 2 strains have been identified that start with motifs A and T.