Cellulose is the most abundant biological polymer on Earth. It is found in wood and cotton, and forms the basic structural foundation of the cell wall of almost all eukaryotic plants. Bacteria are known to secrete cellulose as part of their metabolism of glucose and other sugars. The focus of this review is upon bacterial cellulose synthesis. We emphasize recent literature directed primarily upon Acetobacter xylinum, which has been most widely studied. Our review covers the following topics relating to cellulose synthesis: genetics, biochemistry, ultrastructure, growth conditions, and ecological considerations as they relate to the diversity of microbes capable of synthesizing this abundant, unique polymer--cellulose.