The S-layer is a paracrystalline mono-layered assembly of proteins which coats the surface of bacteria. Probably acts as a physical barrier to parasites and lytic enzymes. This bacterium is covered by a S-layer with hexagonal symmetry. Secreted by an ABC transporter (type I) secretion apparatus. The calcium binding of this protein may mediate surface attachment by ionic bridging between the S-layer and a specific membrane-associated oligosaccharide.