The cellulose-producing bacterium Acetobacter xylinum has been considered a strict aerobe, and it has been suggested that the function of cellulose is to hold cells in an aerobic environment. In this study, we showed that A. xylinum is capable of growing microaerophilically. Cellulose pellicles provided significant protection to A. xylinum cells from the killing effects of UV light. In experiments measuring colonization by A. xylinum, molds, and other bacteria on pieces of apple, cellulose pellicles enhanced colonization of A. xylinum on the substrate and provided protection from competitors which use the same substrate as a source of nutrients. Cellulose pellicles produced by A. xylinum may have multiple functions in the growth and survival of the organism in nature.