Genes <i>bb0562</i>-<i>bb0564</i> are dispensable for <i>B</i>. <i>burgdorferi</i> survival and replication in ticks but <i>bb0562</i> is important for mouse infection by tick bite transmission.

Naïve Ixodes scapularis larval ticks were artificially infected with B. burgdorferi clones by immersion. B. burgdorferi densities in ticks were assessed at each stage of tick development before and after feeding to repletion on mice by performing quantitative PCR analysis of total DNA isolated from ticks (A-C) or plating of dilutions of whole triturated ticks in solid or liquid BSK medium (D). Statistical analyses were performed using the one-way ANOVA with Dunnett’s multiple comparisons test to WT, GraphPad Prism 9.0.0. (**pB. burgdorferi infected nymphs were fed to repletion on groups of 3–7 naïve C3H/HeN mice per B. burgdorferi clone. Mice were assessed for infection three weeks post-tick feeding. Ear, heart, bladder, and joint tissues were collected and analyzed for spirochete reisolation in culture medium. Numbers above each data column represent the total number of culture positive tissues out of the total number of tissues analyzed.