Electron microscopic evidence of flagella and pili on Legionella pneumophila.

Twenty-one strains of Legionella pneumophila, representing the six known serotypes of the organism, cultured on various bacteriological media and in the yolk sacs of fertile hens' eggs were examined by negative stain electron microscopy for flagella and pili. These appendages were usually observed after cultivation on media capable of inducing an early profuse growth of the organisms.