ABSTRACT
The Legionnaires' disease organism was eventually classified in the new family Legionellaceae, as Legionella pneumophila. L. pneumophila, and the seven other named species of Legionella are fastidious bacteria. The first DNA relatedenss studies to characterize L. pneumophila were done before the guanine plus cytosine content of its DNA was known. The family Legionellaceae was proposed by Brenner et al. in 1979. The name means the Legionella family. Legionellaceae are functionally defined as Gram-negative rods 0.3 to 0.9 µm in width by 2 to 20|xµ or more in length. Legionellaceae are oxidase-negative or weakly oxidase-positive. They do not reduce nitrates, hydrolyze urea, or metabolize carbohydrates. They liquefy gelatin. The family Legionellaceae, the genus Legionella, and its type species, L. pneumophila were proposed in 1979 by investigators at Centers for Disease Control. There is general agreement that a species can be defined genetically as a group of strains with DNAs that are 70% or more related.
