The Differentiation of Certain Genera of Bacteriaceae by the Morphology of the Microcyst Stage

SUMMARY: The microcysts or resting cells of Bacteriaceae have three typical forms, which are regular and recognizable, and by which the Family may be divided into three groups.

The first type of microcyst is small, oval and eccentrically nucleate; it is typical of Bacterium coli, and Proteus, Pseudomonas and Salmonella spp. with the exception of Salm. typhi which forms a very large, oval microcyst, with a central nucleus. The microcysts of Shigella spp. resemble those of Salmonella typhi. Bacterium aerogenes produces large, spherical or oblong microcysts with a small, central nucleus.