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.

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 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.

Microbiological Classification

Microbiological Characteristics

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].

Life Cycle

  • 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.

Gallery

Colorized scanning electron micrograph (SEM) depicted a large grouping of Gram-negative Legionella pneumophila bacteria under 8000x magnification.Courtesy of Janice Haney Carr, Public Health Image Library[5]
Colorized scanning electron micrograph (SEM) depicted a large grouping of Gram-negative Legionella pneumophila bacteria under 10,000x magnification.Courtesy of Janice Haney Carr, Public Health Image Library[6]
Legionella micdadei bacteria using TATLOCK conjugate in egg yolk sac suspension, DFA-stained photomicrograph with positive HEBA stain.Courtesy of Ann Herbert, Public Health Image Library[7]

References

  1. Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed. ed.). McGraw Hill. ISBN 0-8385-8529-9.
  2. Ewann F, Hoffman PS (2006). "Cysteine metabolism in Legionella pneumophila: characterization of an L-cystine-utilizing mutant". Appl Environ Microbiol. 72 (6): 3993–4000. doi:10.1128/AEM.00684-06. PMC 1489648. PMID 16751507.
  3. 3.0 3.1 Swanson MS, Hammer BK (2000). "Legionella pneumophila pathogesesis: a fateful journey from amoebae to macrophages". Annu Rev Microbiol. 54: 567–613. doi:10.1146/annurev.micro.54.1.567. PMID 11018138.
  4. Oliva G, Sahr T, Buchrieser C (2018). "The Life Cycle of L. pneumophila: Cellular Differentiation Is Linked to Virulence and Metabolism". Front Cell Infect Microbiol. 8: 3. doi:10.3389/fcimb.2018.00003. PMC 5780407. PMID 29404281.
  5. Haney Carr, Janice. "Public Health Image Library". www.cdc.gov. Retrieved Jan 15 2016. Check date values in: |access-date= (help)
  6. Haney Carr, Janice. "Public Health Image Library". www.cdc.gov. Retrieved Jan 15 2016. Check date values in: |access-date= (help)
  7. Herbert, Anne. "Public Health Image Library". www.cdc.gov. Retrieved Jan 15 2016. Check date values in: |access-date= (help)