L.pneumophila is a ubiquitous aquatic organism that thrives in warm environments (32°- 45°C). L. pneumophila is a 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.

• Bacteria; Proteobacteria; Gammaproteobacteria; Legionellales; Legionellaceae

• L.pneumophila is a ubiquitous aquatic organism that thrives in warm environments (32°- 45°C).
• L. pneumophila is a 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.^[1]
• 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.

Legionella grow on buffered charcoal yeast enriched with L-cysteine ^[2]

• The natural habitat of Legionella is freshwater, where they often live within protozoa such as Vermamoeba vermiformis, Acanthamoeba spp., Tetrahymena pyriformis, and Naegleria spp ^[3]. It utilizes a similar method to enter and infect phagocytes ^[3].

• One of the unique characteristics of Legionella pneumophila is that is has the ability to thrive within a large variety of hosts ^[4].
• 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 infectivity.
• In the second phase, called the infectious phase, the bacteria are shorter and thicker.