The ultrastructure of stressed Legionella pneumophila

Legionellae are able to survive in natural environments which kill many other organisms. The reason for this stress resistance is not well understood nor have its morphological correlates been investigated. The ultrastructure of Legionella pneumophila subjected to stress by heat, acid and starvation, was studied by transmission electron microscopy. Heat-treated cells showed little change although cell shape tended to be distorted. Acid-treated cells showed severe shrinkage of cytoplasmic contents. Starvation caused a reduction in cell size, and after 1 month of starvation cells became fragile, although viability was not reduced.