NR2E3 and Lyme disease: Cross-genome comparisons between the Lyme disease spirochaete and the relapsing fever spirochaetes (B. hermsii, B. recurrentis and B. duttonii), which encode an operon for a class Ib RNR (Barbour et al., 2005; Pettersson et al., 2007; Lescot et al., 2008), did not identify similar gene(s) in B. burgdorferi (Barbour et al., 2005; Pettersson et al., 2007).