Figure 1

Genomes and membranes in eukaryotes and prokaryotes. (a). TEM of cyanobacteria, showing large expansion of bioenergetic membrane surface area as internal thylakoid membranes. However, cyanobacteria are sufficiently small that one or a few copies of the genome (not visible) are sufficient to retain control over chemiosmotic coupling. Scale bars: 50 nm. Reproduced with permission from Miller SR et al. PNAS 2005, 102:850-855. (b). TEM of intracellular bacteria living within free-living cyanobacteria (Pleurocapsa minor): one of only two known examples of a prokaryote inside a (walled) prokaryote, which must have gained entry without phagocytosis. Scale bars: 1 μM. Reproduced with permission from Wujek D. Trans Am Micros Soc 1979, 98:143-145. (c). Multiple copies of nucleoids, each containing the complete genome of Thiomargarita, stained with DAPI. Giant vacuole above in black. Scale bar 50 μM. Courtesy of Heide Schultz-Vogt. (d). Extreme polyploidy in Epulopiscium, (stained with DAPI) showing peri-membrane location of nucleoids, each genome about 3.8 Mb in size. Scale bar 50 μM. Courtesy of Esther Angert.