4 and 5). However, narrow extensions of ribosome-containing cytoplasm seem to connect such superficially separate membrane-bounded regions, suggesting there is only one major membrane-bounded ribosome and nucleoid-containing organelle. The complexity of the way in which the ICM can enclose the membrane-bounded

ribosome-containing region within the ribosome-free paryphoplasm (that is, the way in which the paryphoplasm can surround the ICM) is illustrated in Fig. 5, where there is a large invagination of paryphoplasm at one cell pole and where continuity of this region with the HDAC inhibitor outer rim of paryphoplasm is apparent. Thus, the underlying topology of the cell plan in Prosthecobacter is that of a large ribosome- and nucleoid-containing compartment equivalent to the planctomycete pirellulosome, bounded by a single ICM membrane HSP990 separating that compartment click here from a ribosome-free paryphoplasm. Figure 4 Transmission electron micrograph of high-pressure frozen and cryosubstituted cell of Prosthecobacter dejongeii , showing prostheca (PT), an intracytoplasmic membrane (ICM) surrounding a pirellulosome region containing a condensed fibrillar nucleoid (N), and a paryphoplasm region (P). Inset: enlarged view of region of cell outlined in the white box showing cytoplasmic

membrane (CM), paryphoplasm (P) and ICM. Bar – 500 nm. Figure 5 Transmission electron micrograph of high-pressure frozen and cryosubstituted cell of Prosthecobacter dejongeii showing an intracytoplasmic membrane (ICM) surrounding a pirellulosome region containing a fibrillar nucleoid (N), paryphoplasm region at cell rim and a large invagination of rim paryphoplasm (P) at the cell pole. Inset: enlarged view of region

of cell periphery showing continuity of the paryphoplasm at the cell rim with a large polar invagination of paryphoplasm, which is bounded by ICM which also defines an extension of the pirellulosome’s riboplasm into the cell pole (see arrowheads). Tenoxicam Bar – 500 nm. Immunogold labeling of double-stranded DNA shows that the DNA is, as expected, coincident with the dense fibrillar nucleoid located within the major membrane-bounded compartment of the cell (Fig. 6). Figure 6 Transmission electron micrograph of high-pressure frozen and cryosubstituted cell of Prosthecobacter dejongeii , immunogold labeled using anti-double-stranded DNA mouse monoclonal antibody and goat anti-mouse IgG bound to 10 nm-colloidal gold, showing labeling only over the condensed fibrillar nucleoid (white arrowheads) in the pirellulosome bounded by an intracytoplasmic membrane (ICM). Bar – 200 nm. Cell compartmentalization in Chthoniobacter flavus In high-pressure frozen and cryosubstituted Chthoniobacter flavus, as in V. spinosum and P. dejongeii, cells were found to possess two major compartments separated by a membrane analogous to those characteristic of the planctomycete cell plan.