IDENTIFICATION OF THE ASPARTATE-BETA-SEMIALDEHYDE DEHYDROGENASE GENE OF LEGIONELLA-PNEUMOPHILA AND CHARACTERIZATION OF A NULL MUTANT

The ability of Legionella pneumophila to cause Legionnaires' disease i s dependent on its capacity to survive in the intracellular environmen t of its host cells. Furthermore, outbreaks of this disease have been associated with contaminated water sources where L. pneumophila surviv es as a parasite of protozoa. in this study, we determined the effect of nutritional auxotrophy on the ability of L. pneumophila to survive in the intracellular environment of its host cells, We generated a dia minopimelic acid (DAP) auxotroph (AA400) oft. pneumophila by disruptio n of the aspartate-P-semialdehyde (asd) gene. The ability of AA400 to survive within macrophages and protozoa was found to be defective. Thi s defect was due solely to the asd disruption since complementation of the mutant with the wild-type asd gene restored its capacity for intr acellular survival. Furthermore, the defect was not completely complem ented by DAP supplementation to the culture media, Thus, our results s uggest that disruption of the nsd gene may prove to be useful in the d esign of attenuated vaccines against Legionnaires' disease.