Identification and Evolution of ATP/ADP Translocases in Rickettsia species

This report deals with the identification of ATP/ADP translocase genes. In rickettsial species such as Rickettsia prowazekii, which is the cause of epidemic typhus in humans, the utilisation of host cell ATP is the major way that this bacterium employ its toxicity in the host cell. This obligate intracellular bacterium is an energy-parasite. In the genome of R. prowazekii there are five homologs of the ATP-ADP translocase gene; at least four of them are actively transcribed in rickettsias growing in mammalian cell cultures. R. rickettsii is the cause of Rocky mountain spotted fever and R. typhi causes murine typhus in humans. In this work it is shown that the species R. rickettsii and R. typhi share the ability of their close relative R. prowazekii to transport ATP across the inner bacterial membrane. Four homologs have been identified in R. typhi and three homologs have been identified in R. rickettsii. The phylogenetic analysis in this work shows that the ATP/ADP translocase homologs in R. prowazekii, R. rickettsii and R. typhi share a common origin. My data suggests that five homologs existed, prior to speciation. The phylogeny for the ATP/ADP translocase genes presented here follows the 16S rRNA phylogeny for these rickettsial species presented elsewhere