Legionella
Legionella
Legionella is a genus of rod-shaped, Gram-negative bacteria that naturally occur in low concentrations in surface and groundwater environments. They are obligate aerobes and typically possess flagella for motility. A defining characteristic is their ability to replicate intracellularly within protozoa such as amoebae, which protects them from environmental stress and disinfectants. In humans, they are clinically significant as the causative agents of Legionnaires' disease and Pontiac fever, particularly when they proliferate in man-made water systems.
Details
Identification
Thin, Gram-negative rods; require specialized L-cysteine-enriched media (BCYE agar) for growth; biochemical identification via MALDI-TOF MS.
Social behavior
Formation of biofilms and symbiotic interaction with protozoa as host cells.
Diet
Utilize amino acids as their primary energy source; typically derive nutrients directly from the cytoplasm of their host cells (protozoa).
Hunting strategy
Infection of host cells by inducing phagocytosis and bypassing lysosomal digestion.
Overwintering
Persistence within amoebic cysts or biofilms during low temperatures.
Ecology
Ecological role
Regulation of microorganism populations in aquatic ecosystems through parasitism.
Natural predators
Bacterivorous protozoa (if infection fails), bacteriophages.
Competitor species
Other biofilm-forming bacteria such as Pseudomonas aeruginosa.
Ecosystem service
Part of the microbial food web and nutrient recycling in aquatic environments.
Threats
Thermal disinfection (> 60 °C), UV irradiation, biocides (e.g., chlorine).
Scientific profile
Profile
Habitat
Natural freshwater habitats (lakes, rivers, groundwater) in low concentrations. Man-made water systems (hot water tanks, plumbing, air conditioning) provide optimal conditions due to stagnation and biofilms.
Ecological role
Component of the natural aquatic microbiome. They act as parasites of protozoa, thereby influencing the microbial community structure in water bodies.