Borrelia burgdorferi gene expression from inside its tick vector during a bloodmeal

Borrelia burgdorferi, the causative agent of Lyme disease, is transmitted to vertebrate hosts by Ixodes ticks. As it moves from tick to host, B. burgdorferi must adapt to survive in a vastly different environment. During the tick bloodmeal, which lasts several days, B. burgdorferi is primed for mammalian infection, growing increasingly virulent as it senses cues from its surroundings in the tick. This conditioning is dependent on key transcriptional regulators; however, the downstream transcriptional changes occurring inside of the tick that promote B. burgdorferi transmission and infection are poorly understood due to technical difficulties in sequencing the B. burgdorferi transcriptome from inside of ticks. We developed a protocol to enrich and sequence B. burgdorferi from inside the tick, and we measured global transcriptional changes occurring in feeding ticks. We identified 192 genes that change expression twofold over the course of the tick bloodmeal, which were predominantly located on the plasmids of the genome. The majority of the upregulated genes encode proteins found at the cell envelope or proteins of unknown function, including 45 upregulated genes encoding outer surface lipoproteins. These genes that increase during feeding are candidates for future functional studies, which can help identify new targets for methods that aim to control the spread of Lyme disease. We profiled gene expression from Borrelia burgdorferi enriched from ticks feeding on mice across four days of a bloodmeal (1 day, 2 days, 3 days, and 4 days after attachment).