show Abstracthide AbstractPseudomonas aeruginosa bacteria can display highly divergent phenotypes. This is reflected by a high genomic variability, as typically 10 – 20 % of the genome is made up by DNA specific for clonal lineages or even single isolates. Therefore, a large and diverse pangenome is assumed for this species. In order to characterize composition and size of the pangenome, we performed genome sequencing for 20 unrelated P. aeruginosa isolates. These isolates represent the 15 most prominent clonal lineages of the worldwide P. aeruginosa population and 5 lineages which had not been found among clinical samples at the time of selection. Thus genome comparisons of these 20 isolates should allow a comprising view on the pangenome of this bacterial species characterized as an opportunistic pathogen with high metabolic versatility.