The development of Chlamydia trachomatis inclusions within the host eukaryotic cell during interphase and mitosis.

The dynamic nature of Chlamydia trachomatis inclusions was studied by video and 35 mm time-lapse photomicrography of live cells, and by immunolocalization of inclusions in fixed cells. A serotype E isolate was used to infect the MCCoy cell line and endometrial epithelia. Then resulting inclusions were observed over 4 d. They appeared as slowly expanding fluid-filled membrane vesicles whose growth varied considerably, and which were subject to great physical distortion by the host cell during interphase and mitosis. When this distortion became extreme the inclusion was observed to divide. However, as inclusions were mobile within the cytoplasm and thus able to come into contact with each other, there was a net tendency for the opposite process of inclusion fusion to occur when cells contained more than one inclusion. The proportion of infected cells decreased with time as a result of host cell proliferation, despite transmission of inclusions to progeny at the time of mitosis. Inclusion growth physically disrupted karyokinesis and cytokinesis so that host cell division became distorted or blocked on the second or third day of infection. Cell death eventually occurred by a very rapid lysis event.