Variability of lexA gene in Clostridium difficile . Representation of the C. difficile 630 strain lexA nucleotide sequence in comparison to repressor sequences of 62 other strains. Grey arrow denotes the nucleotide sequence of the CD630 lexA gene. Black arrows mark the position of domains in LexA. The number of strains with specific SNP and the corresponding nucleotide/aminoacid change is marked above the arrow. The ordinal number of nucleotides in lexA is presented below the arrow. The SNPs marked in blue encompass strains from cluster III, composed mainly of strains belonging to the toxinotype V. The position of the cleavage site and the catalytic residues is marked in purple.