More than 30 years have passed since Legionella pneumophila, the causative agent of Legionnaires' disease, was identified as a new human pathogen. First recognized due to the epidemic of pneumonia that followed the 1976 Legionnaires' convention in Philadelphia, USA, legionellosis is still a disease of medical and public interest. Legionella is commonly found in aquatic habitats, where its ability to survive and to multiply within different protozoa equips the bacterium to be transmissible and pathogenic to humans. However, these very traits also make Legionella a favoured model system to analyse the mechanisms by which bacteria survive, acquire nutrients, and replicate within macrophages and the lung.

With the application of modern molecular genetic and cell biological techniques, we have begun to understand the mechanisms used by L. pneumophila to multiply within protozoa and alveolar macrophages. Also, we have gained insight into the specific regulatory cascades that govern cell cycle-dependent differentiation as well as the general mechanisms of gene regulation in L. pneumophila.

Thanks to the recent publication of the genome sequences of four L. pneumophila strains, it is now feasible to investigate the whole genome in silico, the transcriptome via microarrays, and the proteome by two-dimensional gel electrophoresis. Thus, new questions can be asked and impressive amounts of data can be generated and evaluated. Furthermore, research in the fields of clinical features, diagnosis, treatment and epidemiology continues to generate new strategies for management and prevention of disease and more questions for basic scientists.

A newly published book on Legionella covers a wide range of topics from the history of the identification of Legionella and clinical disease treatment, to the microbe’s gene expression and secretion systems as well as its strategies for intracellular multiplication and nutrient acquisition. The book is recommended for all microbiology libraries.

Further details at Legionella: Molecular Microbiology