The Story of Legionella: From Surviving Inside Amoebas to Causing Pneumonia

Legionella pneumophila is type of bacteria present in natural water sources, such as rivers, ponds, and in man-made water reservoirs, such as water fountains. Amoebas are single-celled organisms that also live in water sources and generally feed on bacteria. However, Legionella are not digested by amoebas and have even evolved to multiply inside the amoebas that try to digest them! This resistance to being eaten by amoebas has enabled the Legionella bacteria to survive in water sources and to be transmitted to humans through contaminated water droplets. Their ability to survive inside amoebas also allows Legionella bacteria to survive and multiply within cells in the human lungs, leading to pneumonia. Therefore, the long relationship between Legionella and amoebas helped Legionella to evolved and to infect human macrophages causing disease.