A proposed life cycle for the Reiter treponeme.

Direct microscopical observations of single developing cysts in sealed slide microcultures prepared from 5-days-old tube cultures of the Reiter treponeme revealed two distinct phases in the life cycle. In one phase transverse fission was the main method of multiplication while in a second phase, occurring when conditions in the medium became unfavourable for propagation, cysts developed. These could release large numbers of actively motile treponemes when returned to optimum growth conditions. These observations, together with results of the dilution method for the calculation of the Most Probable Number and the absence of a response in treponemes killed by high temperature (45 degrees C) or abnormal pH (10), showed that the cysts were viable and a mode of propagation for the Reiter treponeme.