[The ultrastructure of a new species of Chlamydia--Chlamydia pneumoniae].

: The dynamic study of a new Chlamydia species, C. pneumoniae (strain TWAR, isolate TW-480), inoculated into the monolayer culture of cells L-929 was made 24, 48, 72 and 96 hours after inoculation. When compared with C. trachomatis and C. psittaci, C. pneumoniae were found to stand between these two species with respect to the morphology of their intracytoplasmic microcolonies (inclusions): they were round, almost bubble-like, but more densely packed with chlamydiae, surrounded by an undulate membrane, preserving its integrity until the late stages of their development cycle. In cells L-929 C. pneumoniae had a typical development cycle accompanied by the formation of vegetative and spore-like cells, reticular and elementary bodies, as well as intermediate cells, though this process was slower than in C. trachomatis and C. psittaci. Besides normal elementary bodies, many altered ones were formed in the process of the development of C. pneumoniae in cells L-929. Most of these alterations were similar to the process of bacterial L-transformation and could be regarded as the manifestation of chlamydial pathology related to the adaptation to new host cells.