This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Infectious B. burgdorferi strains that have increased transformability with the shuttle vector pBSV2 were recently constructed by inactivating the gene encoding BBE02, a putative restriction-modification gene product expressed by the linear plasmid lp25 (Kawabata et al., Infect. Immun. 72:7147-7154, 2004). Absence of the linear plasmid lp56, which carries another putative restriction-modification gene, further enhanced transformation rates. Infectivity of these mutants was assessed previously in mice that were inoculated with needle and syringe, and was found to be equivalent to that of wild type spirochetes. Here we examined the infectivity of spirochetes to ticks after capillary inoculation of Ixodes scapularis nymphs, and the subsequent spirochetal infectivity to mice via ticks, using B. burgdorferi B31 clonal isolates lacking lp56 and/or BBE02. The absence of lp56 (but not BBE02) correlated with a lower number of spirochetes in ticks after feeding on mice; this plasmid thus may play a role, albeit not an essential one, in supporting spirochetal survival in the feeding tick. Importantly, however, absence of lp56 and BBE02 did not detectably influence infectivity to mice via ticks.
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