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Chapter 89 : Genome Sequencing and Genomics
This chapter explores issues related to Legionella genomics. A critical breakthrough in this area recently occurred with the determination of the genome sequences of three clinical, serogroup 1 isolates of Legionella pneumophila subsp. pneumophila. The three strains are L. pneumophila Paris, Lens and Philadelphia-1. The genome sequences obtained from these three strains have already proven to be incredibly useful as a genetic tool and they have provided numerous new and valuable insights into the biology of L. pneumophila. Analysis of the completed genome sequences of L. pneumophila strains Paris, Lens and Philadelphia-1 revealed that each consists of 3.3 to 3.5 million base pairs, encodes approximately 3,000 genes, and has an average G+C content of 38%. Since the three analyzed strains belong to the same species and same serogroup, this level of diversity is remarkable. Several additional insights that have been derived from genomic analyses include the marked plasticity of the genomes, the evidence of large-scale rearrangements, and the presence of a large number of eukaryotic-like proteins. The availability of a large number of different genome sequences of Legionella will clearly benefit the community and pave the way for in-depth comparative genomics. In summary, the field of Legionella genomics has only begun and promises a bright future.