Function and Expression of Legionella pneumophila Surface Factors

This chapter focuses on the major infectivity potentiator protein (Mip) protein and the function and expression of the flagellum of Legionella pneumophila. The Mip protein forms a homodimer on the bacterial surface; each monomer consists of a proximal and a peripheral domain. The contact regions between the two monomers seem to be located at the N-terminal part of the protein. Motility is an important factor to find a new host for another cycle of intracellular replication and for colonization of new habitats. Flagellated bacteria have been found in lung alveolar spaces of patients with legionellosis. It was shown that expression of the virulent phenotype and motility is regulated coordinately. A gentamicin infection assay revealed a clear difference in the number of intracellular bacteria at the onset of multiplication. L. pneumophila is found in very different habitats and it is able to replicate intracellularly in many host cells. Researchers recently demonstrated that regulation of fiaA expression is modulated by different environmental factors, such as temperature, growth phase, osmolarity, viscosity, and the nutrient stage.