D. radiodurans cell division on TGY agar at 30°C. D. radiodurans cell division on TGY agar at 30°C. (A) Cell division monitored by time-lapse fluorescent microscopy starting from a single diad (see Video S1 in the supplemental material). Images were obtained with a fluorescent microscope (Zeiss Axiovert 200 M). Membranes were stained with FM 4-64 (red), and nucleoids were stained with 4′,6-diamidino-2-phenylindole (DAPI) (blue). Septa are formed perpendicular to the cross wall, separating the two cells in a diad (step 1). Septation creates two new cross walls, and two diads are formed as a result. Perpendicular to the previously formed cross walls, new septa invaginate into four cells with nuclear material in the process of separating into daughter cells (step 2). This stage of cell division represents two tetrads. Complete septation results in four new cross walls that give rise to four diads (step 3). New septa invaginate perpendicular to the previously formed cross walls, giving rise to four tetrads (step 4). The following round of cell division produces eight tetrads (step 5). (B) Phase contrast-image of a microcolony obtained from a single tetrad. Dea Slade, and Miroslav Radman Microbiol. Mol. Biol. Rev. 2011; doi:10.1128/MMBR.00015-10