Recent analysis that looked for recombination throughout the whole genome revealed

significant levels of HGT both within the species L. pneumophila and from other Gamma-Proteobacteria especially those, that like legionellae, are associated with amoebae [16]. A comprehensive review of the current knowledge about the population genetics, phylogenetics and genome of L. pneumophila concluded that recombination is playing a role in diversifying the species but this may have been more significant in the past than is seen with the current population of the species [17]. The EWGLI SBT database has now grown significantly since the work described in earlier publications with the addition of a seventh allele (neuA) and the designation of Sequence Types (STs) [18].

The database contained 838 distinct sequence types at the time PI3K inhibitor of this study and these were derived from strains isolated from worldwide locations in contrast to other studies that used more localised samples sets. Therefore, in light of this large increase in novel STs, the aims of this study were; 1) To evaluate this global dataset and assess the relative contribution of recombination mediated by HGT and mutation to genome evolution.   2) To derive a method to cluster strains of similar genotype based on the type of population structure found in the first part of this study. This would provide a set of pragmatic groups that could be labelled and referred to using a common terminology within the Legionella scientific community.   3) To sequence the genomes learn more of isolates representative of these major clusters within the population and provide an overview of the population structure. This would enable comparison of the genetic types determined by SBT with that derived by examining the diversity within the whole genome.   4) The ultimate aim was to provide a set of sequenced

strains, which adequately represent the L. pneumophila pan genome. This will enable further studies where Erythromycin strains within a cluster are investigated in more detail, and allow testing of the hypothesis that clusters of strains are likely to share a common lineage and therefore some phenotypic similarities.   Results and Discussion Sequence Based Typing analysis: Recombination Tests Choice of the best algorithm with which to cluster the sequence types of L. pneumophila will be informed by the population structure of the species, which will in turn be influenced by the relative contributions of recombination and mutation to sequence evolution. Therefore the frequencies of intergenic and intragenic recombination in L. pneumophila were investigated and compared to those for Staphlococcus aureus (representing a comparatively clonal species), Streptococcus pneumoniae (representing an intermediate species) and Neisseria meningitidis (representating a panmictic species).