Outer membrane-spanning porin, Oms66 (P66) (Skare et al., 1997).  This porin has a β-barrel structure (Kenedy et al. 2013) and pore diameters at the mouth of 1.6nm and at the central constriction of 0.8nm (Bárcena-Uribarri et al. 2013). Oms66 plays a role in resistance to host immune defenses (Curtis et al. 2018). The contribution of P66 porin function to B. burgdorferi pathogenesis has been evaluated (Fierros et al. 2024).