Studies on the ultrastructure of Bordetella pertussis. I. Morphology, origin, and biological activity of structures present in the extracellular fluid of liquid cultures of Bordetella pertussis.

Two distinct particles have been recognized in the extracellular fluid of B. pertussis cultures. Both appeared to arise from the surface (cell wall) of the organism. One of these, a membranous particle, seemed to derive from long projections on the organism composed of the outer membrane of the cell wall. The second particle, a fine filament, was not readily comparable with any previously described bacterial structure. The two particles could be separated from each other by gradient centrifugation in CsCl. Lymphocytosis-promoting factor and histamine-sensitizing activity were only associated with fractions containing the fine filaments.