Streptomyces lividans 66 producing poly-N-acetylglucosamine (PNAG). The image shows a mycelium from an 18 h old liquid-grown culture of the matAB double mutant genetically complemented by introduction of a plasmid expressing matAB. PNAG was stained with monoclonal antibody mAb F598 (yellow). To visualize the hyphae, the DNA was stained with PI (red). Image by Dino van Dissel and Gilles P. van Wezel (Leiden University, The Netherlands); image modified by MIC. The cover is published under the Creative Commons Attribution (CC BY) license.