Fimbriae, also known as pili, form filaments radiating from the surface of the bacterium to a length of 0.5-1.5 micrometres. They enable the cell to colonise host epithelia. This family constitutes the major subunits of CS1 like pili, including CS2 and CFA1 from Escherichia coli, and also the Cable type II pilin major subunit from Burkholderia cepacia [1]. The major subunit of CS1 pili is called CooA. Periplasmic CooA is mostly complexed with the assembly protein CooB. In addition, a small pool of CooA multimers, and CooA-CooD complexes exists, but the functional significance is unknown [1]. A member of this family has also been identified in Salmonella typhi and Salmonella enterica [2].

1: New tools in an old trade: CS1 pilus morphogenesis. Sakellaris H, Scott JR; Mol Microbiol 1998;30:681-687. PMID:10094617

2: Multiple insertions of fimbrial operons correlate with the evolution of Salmonella serovars responsible for human disease. Folkesson A, Advani A, Sukupolvi S, Pfeifer JD, Normark S, Lofdahl S; Mol Microbiol 1999;33:612-622. PMID:10417651