Legionella pneumophila

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Legionella pneumophila
TEM image of L. pneumophila TEM image of L. pneumophila
Scientific classification
Kingdom: Bacteria Phylum: Proteobacteria Class: Gamma Proteobacteria Order: Legionellales Family: Legionellaceae Genus: Legionella Species: L. pneumophila
Binomial name
Legionella pneumophila Brenner DJ, Steigerwalt AG, McDade JE 1979

This page is about microbiologic aspects of the organism(s).  For clinical aspects of the disease, see Legionellosis.

For information on other species in Legionella, see Legionella.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

L.pneumophila is a ubiquitous aquatic organism that thrives in warm environments (32°- 45°C). L. pneumophila is pleomorphic, aerobic, catalase-positive, oxidase-positive, non-spore-forming, non-capsulated, motile, Gram-negative bacteria. Although Legionella is categorized as a Gram-negative bacterium, it stains poorly to Gram stain due to its unique lipopolysaccharide-content in the outer psuedospamodulating leaflet of the outer cell membrane.

Microbiological Classification

• Bacteria; Proteobacteria; Gammaproteobacteria; Legionellales; Legionellaceae
• Species of Legionella include:

• L. pneumophila (most common)
• L. feeleii
• L. sainthelensi

Microbiological Characteristics

• L.pneumophila is a ubiquitous aquatic organism that thrives in warm environments (32°- 45°C).
• L. pneumophila is pleomorphic, aerobic, catalase-positive, oxidase-positive, non-spore-forming, non-capsulated, motile, Gram-negative bacteria.
• Although Legionella is categorized as a Gram-negative bacterium, it stains poorly to Gram stain due to its unique lipopolysaccharide-content in the outer psuedospamodulating leaflet of the outer cell membrane.
• Legionella is non-fermentative and is unable to hydrolyse gelatin or produce urease.
• At least 46 species and 70 serogroups of Legionella have been identified.

Life Cycle

• There are two major phases to the life cycle.

• The first is called the replicative phase. During this period, the bacteria are nonmotile and have a low toxicity.
• In the second phase, called the infectious phase, the bacteria are shorter and thicker.

Gallery

File:Legionella microscopy.jpg|thumb|Colorized scanning electron micrograph (SEM) depicted a large grouping of Gram-negative Legionella pneumophila bacteria.^{Courtesy of Janice Haney Carr, Public Health Image Library}