Distribution of single-nucleotide polymorphisms (SNPs) along 330 kb of the genomes of L. pneumophila HL 0604 1035, Philadelphia and Lorraine. The number of SNPs (y axis) is plotted according to the position of the corresponding 500 bp fragment on the strain Paris chromosome (x axis). A straight blue line indicates 0 polymorphism between the two strains. Numbers on the scale bar indicate the percentage of polymorphism. The green (+ strand) and red (- strand) lines depict the corresponding genes.