Question

in 1976, an outbreak of pulmonary infections among participants at an American Legion convention in Philadelphia led to the identification of a new disease, Legionnaire's disease. The bacterium responsible for the disease had never before been known to be pathogenic. From your knowledge of bacterial genetics, can you postulate how it might have acquired the ability to cause disease

Answer 1

The Legionella bacterium is a small, aerobic, waterborne, gram-negative, unencapsulated bacillus that is nonmotile and oxidase and catalase positive

Acquired ability to cause disease :- a)An essential step in the development of infection and disease progression is the ability of intracellular pathogens to exit the host cell once replication has ceased, thereby allowing infection of new host cells.

b)  Legionella avoids interactions with endosomes, fuses transiently with mitochondria, and intercepts ER exit vesicles bearing COP II markers . For the next several hours, the LCV maintains interactions with ER-derived vesicles, and the bacteria replicate in a vacuole surrounded by a membrane that resembles rough ER .
what b point is saying that the host has the innate ability of Legionella to replicate within different protozoa has equipped the bacteria with the capacity to replicate in human alveolar macrophages. But what it acquire is replication in a vacuole surrounded by a membrane that resembles rough ER