Molecular model showing the structure of bacterial cellulose synthase. The membrane-embedded enzyme is used by bacteria to produce cellulose (grey and red spheres). The nascent cellulose strand is elongated by glucose transferred from uridin diphosphate (UDP) glucose molecules (stick model, bottom) one at a time. Cellulose synthesis and membrane translocation (movement out of the cell) are catalysed by bacterial cellulose synthase subunits: bacterial cellulose synthase (Bcs)A (pale blue, intracellular and transmembrane) and bacterial cellulose synthase (Bcs)B a periplasmic membrane anchored protein (blue and yellow outer protein). The bacteria use the cellulose produced to form protective biofilms.