Full text loading...
Chapter 86 : Genetic Diversity of Legionella pneumophila
In order to explore the genetic diversity in a large number of strains, a Legionella biodiversity array was designed containing probes (internal PCR products) specific for all those genes that are variable among the three strains as well as of conserved ones that have known or putative implication in virulence. The gene content of 180 Legionella isolates, 165 Legionella pneumophila strains, and 25 representatives of Legionella species other than L. pneumophila isolated from the environment during epidemics or from sporadic cases were analyzed by DNA-DNA hybridization using the Legionella biodiversity array. L. pneumophila serogroup 1 is largely overrepresented among human legionellosis cases, suggesting that virulence differences exist among different L. pneumophila serogroups and other Legionella species. In order to address this question and to try to find a possible link between virulence differences and a specific pattern of virulence genes, the authors analyzed the distribution of these factors among 180 strains. This study also reports for the first time the distribution of the eukaryotic-like genes identified during sequence analysis among L. pneumophila. In order to better understand plasticity and evolution in L. pneumophila the authors used hierarchical clustering to analyze the hybridization patterns obtained. Despite the high genome plasticity observed, hierarchical clustering of the hybridization results of the genes selected for the Legionella biodiversity array correlates with results of rpoB sequence typing and therefore with phylogeny. The Legionella biodiversity array allowed subdivision of the otherwise indistinguishable group of Paris strains.