PDE6A and infection: This deficiency in infection is most likely a result of the inability of the pdeA mutant to reverse its swimming direction (Sultan et al., 2010) because inactivation of a chemotaxis histidine kinase, cheA2, in B. burgdorferi yielded spirochetes that constantly swim in one direction and were unable to reverse and were also unable to establish infection in mice by either needle or tick (Sze et al., 2012).