Ultrastructural studies of Chlamydia psittaci 6BC in situ in yolk sac explants and L cells: a comparison with gram-negative bacteria.

Chlamydia psittaci (6BC) was grown in yolk sac explants and in L cells and fixed by perfusion in situ to provide undamaged material for comparison with gram-negative bacteria. Reticulate, intermediate, and elementary bodies were all seen to lack a well-defined periplasmic space; intermediate and elementary bodies showed condensations of the nucleoid which differ from common bacterial configurations; and the cytoplasm of highly condensed elementary bodies was much more electron dense than that of the gram-negative bacteria, while retaining its basically particulate nature. These important morphological distinctions are interpreted as reflections of a significantly different cellular level of organization in these two groups of organisms. No important morphological differences were noted in comparisons of the chlamydial particles grown in the two different host systems.