Dear Diary, 

Legionella pneumophila grows in a new host and prefers an amoebic host cell within a biofilm. L. pneumophila attached to the amoebic host and exhausts all resources then turns to motile dispersal phase where it breaks the cell wall to find a new host. It then uses its flagellum to reach the lower respiratory of the new host. L. pneumophila is spread via aerosol droplets and is suspended in air or other gas; the bacterium can be found in any water source. The Legionella antigen and DNA can be detected in both motile or replicative phase. 

Legionella pneumophila showed growth in a chemically defined medium; the medium contained 21 amino acids and inorganic salts. L. pneumophila grew in a liquid defined medium at 37°C and in a complex media, with four isolates, with a 6-hour generation time. The strain of L. pneumophila tested was not stated. Researchers specified the L-Serine, L-methionine, and L-cysteine amino acids were essential for ideal growth. A chemostat catalyzed growth in natural environments with limited resources, at the same temperature rate yielded 38% more culture compared to normal conditions.

 

 

 

In vivo, L. pneumophila replicated via pinching binary fission, intra- and extracellularly. Legionella also underwent non-septate binary fission, producing identical cells. L. pneumophila does not grow spores throughout its life cycle, but it does grow spore produces spore-like laminated envelopes or coats, which function similar to gram-positive spores. The bacterium typically replicates between 25 to 47 degrees, pH levels of 5.5 to 9.2, and the oxygen level concentration between 6.0 to 6.7 mg/liter. Legionella did not replicate in tap water with a concentration less than or equal to 2.2 mg/liter of dissolved oxygen. Rutgers University studied specific strains of L. pneumophila, Gt4, and Gt15. The Gt4 strains of L. pneumophila showed growth between 25 and 30°C while the Gt15 strains grew between 42 and 45°C. The in vivo temperature growth was consistent with the temperature tested at water distributors.

Robyn

 

P.S. Here is an animation of Legionella

 

Here a video on Legionella’s replication

 

Reference

Faulkner, G., and R. A. Garduno. “Ultrastructural Analysis of Differentiation in Legionella Pneumophila.” Journal of Bacteriology, vol. 184, no. 24, 2002, pp. 7025–7041.

Rodgers, F. G., and M. R. Davey. “Ultrastructure of the Cell Envelope Layers and Surface Details of Legionella Pneumophila.” Microbiology, vol. 128, no. 7, 1982, pp. 1547–1557.

Sharaby, Yehonatan, et al. “Temperature-Dependent Growth Modeling of Environmental and Clinical Legionella Pneumophila Multilocus Variable-Number Tandem-Repeat Analysis (MLVA) Genotypes.” Applied and Environmental Microbiology, American Society for Microbiology, 31 Mar. 2017, www.ncbi.nlm.nih.gov/pmc/articles/PMC5377503/.

Wadowsky, R M, et al. “Effect of Temperature, PH, and Oxygen Level on the Multiplication of Naturally Occurring Legionella Pneumophila in Potable Water.” Applied and Environmental Microbiology, U.S. National Library of Medicine, May 1985, www.ncbi.nlm.nih.gov/pmc/articles/PMC238529/.

Warren, W J, and R D Miller. “Growth of Legionnaires Disease Bacterium (Legionella Pneumophila) in Chemically Defined Medium.” Journal of Clinical Microbiology, U.S. National Library of Medicine, July 1979, www.ncbi.nlm.nih.gov/pmc/articles/PMC273092/.