Figure 1. Repair of UV-damaged DNA in the hyperthermophilic archaeon Sulfolobus solfataricus. A culture of S. solfataricus grown at 78 °C was treated with ultraviolet (UV) light with a wavelength of 245 nm for 45 s. The treated and the control cultures were stored in the dark at room temperature for 15 minutes before they were reincubated at 78 °C. To determine the extent of DNA double strand breaks (DSBs), total genomic DNA from UV-treated (+) and control (–) cells were analyzed by gel electrophoresis. The DNA in both samples was intact before (pre-UV) and shortly after UV treatment (0 h). But after 2 h, DNA breakdown was pronounced, as a result of DNA DSBs, visible as a smear on the gel. Then, a remarkable DNA repair proceeded, and after 8 hours small DNA fragments below the compression zone at 600 kilo base pairs (kb) had disappeared in the UV-treated samples. (Sabrina Froels et al., J. Bacteriol., 189, 8708–8718, 2007.)

Figure 2. Electron micrograph of Magnetospirillum gryphiswaldense. The dark (electron-dense) particles in the center of the cell represent a chain of magnetosomes. Each magnetite crystal is around 50 µm in diameter. On either pole of the cell a flagellum can be seen. (Electron micrograph: Dirk Schueler, Munich, Germany.)

Figure 3. Myxobacteria. (a) a swarm of Sorangium cellulosum on an agar plate, showing the typical vein system. The swarm is gliding toward the center of the picture. (b) fruiting body of Chondromyces robustus. (Photographs: Hans Reichenbach, Braunschweig, Germany.)

Figure 4. Micrograph of a chain of five Thiomargarita cells together with a human hair (0.1 mm thick). The cells have a diameter of about 0.3 mm and they shine because of several sulfur globules in their interior. There is a slime sheath outside the cells that holds the Thiomargaritas together. (Micrograph: Heide Schulz-Vogt, Bremen, Germany.)

Figure 5. Electron micrograph of an Ignicoccus hospitalis cell together with its satellite Nanoarchaeum equitans. (Electron micrograph: Harald Huber and Reinhard Rachel, Regensburg, Germany.)