cultures (Fig. 3A and C). Although the frequencies were very low
(approximately 1% of all cells), cellulose fibrils associated with the
F2-2 cells were observed (Fig. 3B). The existence of cellulose fibrils
in F2-2 cells was also confirmed by fluorescence microscopy of
cells stained with 0.005% calcofluor white M2R (see Fig. S2 in the
supplemental material). The cellulose fibrils produced by F2-2
cells (Fig. 3E to G) were more twisted than those produced by the
wild-type (Fig. 3D) or F2-2(pSA-CMCax/k) (Fig. 3H) cells.