CRISPR sequences were identified using the online CRISPRs finding software (http://crispr.u-psud.fr/Server/). The software also searches the identified CRISPR sequences against the cas gene database. All spacer sequences were extracted and a sequence similarity clustering using dnaclust software was performed. BLASTN analysis against the NCBI nucleotide database as well as against the Legionella pan-genome proteome and the NCBI NR database were also performed.