Developmental regulation of the cysteine-rich outer-membrane proteins of murine Chlamydia trachomatis.

The developmental cycle of the obligate intracellular prokaryote Chlamydia trachomatis involves the serial alternation of two distinct morphological forms of the organism. To examine the basis of chlamydial differentiation we have searched for developmentally regulated gene products in this species. Chlamydia-infected cells were pulse-labelled with [35S] cysteine at various stages of development and the products of synthesis examined by SDS-PAGE. Our results indicate that the synthesis of the cysteine-rich outer-membrane proteins is developmentally regulated, occurring only late in the cycle during the conversion of reticulate bodies to elementary bodies. Both hydroxyurea and ampicillin block this conversion; as a result of this blockade the cysteine-rich outer-membrane proteins are not produced in the presence of either drug.