Detection of cellulose with improved specificity using laser-based instruments

Specific detection of cellulose has not been possible using laser based instruments such as laser scanning confocal microscopes (LSCM) and fluorescently activated cell sorters (FACS). Common cellulose dyes are nonspecific and/or nonexcitable with common lasers. Furthermore, many lasers emit wavelengths that overlap with autofluorescence from chlorophyll and other plant molecules. We demonstrate that a cellulase and an isolated bacterial cellulose binding domain (CBD) conjugated to fluorescent dyes can be used for laser detection of cellulose with improved specificity. Cell walls of differentiating tracheary elements and spores of Dictyostelium discoideum were tested in this study. For double labeling, autofluorescence interfering with the rhodamine signal was eliminated by collecting each excitation channel separately followed by computer recombination or by using a narrow band pass barrier filter allowing simultaneous channel collection. Using these methods, cellulose and microtubules tagged with a monoclonal antibody to alpha-tubulin were effectively colocalized in chlorophyll-containing tracheary elements using a LSCM. Also, Dictyostelium discoideum spores labeled or unlabeled with CBD-FITC were separated into two populations by FACS indicating that this tag should be useful in future mutagenesis experiments. Therefore, the presence or absence of cellulose can now be analyzed using common lasers.