Recent analysis of two major cellulases from the proteome of R. albus 8 showed that both carried cellulose-binding modules, but neither possessed an obvious dockerin sequence (25). These enzymes, therefore, appear to be non-cellulosomal, although they might still be retained on the cell surface by other mechanisms. Meanwhile, a number of enzymes from R. albus 8 were also found to carry partially homologous C-terminal sequences that show remarkably broad polysaccharide-binding specificities (26). Although these sequences have potential roles in binding to dietary substrates, it is not ruled out that they might mediate binding of the polylpeptides to carbohydrates on the cell surface, thus providing an anchoring mechanism. Other enzymes from R. albus 8 and from several other R. albus strains have, however, been reported to possess dockerins (27) and a large family of dockerin-containing proteins has been detected in the genome of R. albus 8 (28). The role and importance of cellulosome organization in this species, therefore, seems less clear than in R. flavefaciens, and this attribute may even vary between strains of R. albus.

Based on studies in two R. albus strains (8 and 20) type IV pili have been proposed to be involved in binding cells to cellulose (29-31). The pilAl protein is thought to be a major component of the pius of R. albus 20, while pilA2 is more likely to play a role in pilus synthesis (31).