This family includes bacterial proteins involved in cellulose synthesis. Cellulose synthesis has been identified in several bacteria. In Agrobacterium tumefaciens, for instance, cellulose has a pathogenic role: it allows the bacteria to bind tightly to their host plant cells. While several enzymatic steps are involved in cellulose synthesis, potentially the only step unique to this pathway is that catalyzed by cellulose synthase. This enzyme is a multi subunit complex. This family encodes a subunit that is thought to bind the positive effector cyclic di-GMP. This subunit is found in several different bacterial cellulose synthase enzymes. The first recognized sequence for this subunit is BcsB. In the AcsII cellulose synthase, this subunit and the subunit corresponding to BcsA are found in the same protein. Indeed, this alignment only includes the C-terminal half of the AcsAII synthase, which corresponds to BcsB.