Whole genome analyses of transporters in Spirochetes: Borrelia burgdorferi and Treponema pallidum

The completely sequenced genomes of two spirochetes, Borrelia burgdorferi (Bbu) and Treponema pallidum (Tpa) were analyzed for the distribution of transporter types. Both organisms exhibited fewer proteins with >7 α-helical transmembrane spanners (TMSs), and fewer identified transport systems per megabase pair of DNA than most other prokaryotes analyzed. Each organism exhibits one recognizable ion channel protein of the MscS family. Tpa has twice as many primary carriers as Bbu but lacks PTS permeases that are plentiful in Bbu. Tpa is the only prokaryote so far sequenced which has two F-type ATPases. Large families of secondary nutrient uptake carriers (MFS and APC) that are prevalent in other organisms are essentially lacking in Spirochetes. The largest Spirochete secondary carrier families consist of efflux systems. While both Bbu and Tpa exhibit an unusual degree of transporter diversity, major differences in specificity exist between these two organisms.