The influence of Direct Blue 14 and 53 dyes, both having biphenylenebis(azo) skeletal structure but different sulfonate groups substitution on the structure of the nascent microbial cellulose was examined. The product obtained from the Acetobacter culture in the presence of each dye is a characteristic dye-cellulose complex, and the dye molecule is included between the cellulose sheets in the complex corresponding to the (1(1) over bar 0) plane of microbial cellulose. Due to the inclusion of dyes between the cellulose sheets through hydrogen bonding or van der Waals forces, the hydrogen bonding between cellulose chains of microbial cellulose is hindered. The different position of sulfonate groups has no major influence on the two products except on the uniplanar orientation of the product. Celluloses regenerated from both products are cellulose II, but their fine structures are different from each other.