Phylogenetic reconstruction of the Legionella pneumophila Philadelphia-1 laboratory strains through comparative genomics.

Over 20 years ago, two groups independently domesticated Legionella pneumophila from a clinical isolate of bacteria collected during the first recognized outbreak of Legionnaires’ disease (at the 1976 American Legion’s convention in Philadelphia). These two laboratory strains, JR32 and Lp01, along with their derivatives, have been disseminated to a number of laboratories around the world and form the cornerstone of much of the research conducted on this important pathogen to date. Nevertheless, no exhaustive examination of the genetic distance between these strains and their clinical progenitor has been performed thus far. Such information is of paramount importance for making sense of several phenotypic differences observed between these strains. As environmental replication of L. pneumophila is thought to exclusively occur within natural protozoan hosts, retrospective analysis of the domestication and axenic culture of the Philadelphia-1 progenitor strain by two independent groups als...