Control of morphogenesis in Geodermatophilus: ultrastructural studies.

Geodermatophilus grows in two major forms, a nonmotile irregularly shaped aggregate of coccoid cells (C-form) and a motile budding rod (R-form). Morphogenesis can be controlled by an unidentified factor in Tryptose which is required for maintenance of the organism in the C-form and for differentiation of the R-form to the C-form. Morphogenetic events occur synchronously in the described system. Ultrastructural studies show that the major difference between C- and R-forms is in cells envelope structure. R-form cell walls consist of two layers, an inner transparent membranous layer (10 to 12.5 nm thick) and an outer dense diffuse layer (7.5 to 10 nm). In addition to these layers, the C-form has a thick fibrous layer (30 nm) over the dense layer. This layer appears to be a cementing substance which holds the coccoid cells together.