Morphological and cytochemical study of Chlamydia with EDTA regressive technique and Gautier staining in ultrathin frozen sections of infected cell cultures: a comparison with embedded material.

The cryo-ultramicrotomy technique was applied to study the ultrastructure of Chlamydia using two strains: one of C. psittaci and one of C. trachomatis. It clearly appeared that in both strains reticulate bodies show a high degree of plasticity, contrasting with the rigid spherical appearance of elementary bodies. Ultrastructural cytochemical study shows DNA fibrils dispersed throughout the cytoplasm in reticulate bodies whereas DNA is condensed in a nucleoid in elementary and intermediate bodies. The EDTA regressive technique reveals ribonucleoproteins in reticulate and elementary bodies of both studied strains.