Subcellular distribution of glycanases and related components in Ruminococcus albus SY3 and their role in cell adhesion to cellulose

Aims: To compare the subcellular distribution of glycanase-related componen ts between wildtype Ruminococcus albus SY3 and an adhesion-defective mutant , to identify their possible contribution to the adhesion process, and to d etermine their association with cellulosome-like complexes. Methods and Results: Cell fractionation revealed that most of the cellulase s and xylanases were associated with capsular and cell-wall fractions. SDS- PAGE and gel filtration indicated that most of the bacterial enzyme activit y was not integrated into cellulosome-like complexes. The adhesion-defectiv e mutant produced significantly less (5- to 10-fold) overall glycanase acti vity, and the 'true cellulase activity' appeared to be entirely confined to the cell membrane fractions. Antibodies specific for the cellulosomal scaf foldin of Clostridium thermocellum recognized a single 240 kDa band in R. a lbus SY3. Conclusions: The adhesion-defective mutant appeared to be blocked in exocel lular transport of enzymes involved in true cellulase activity. A potential cellulosomal scaffoldin candidate was identified in R. albus SY3. Signific ance and Impact of the Study: Several glycanase-related proteins and more t han one mechanism appear to be involved in the adhesion of R. albus SY3 to cellulose.