Characterization of the rnpB gene and RNase P RNA in the order Chlamydiales

The sequence of the RNase P RNA gene (rnpB) was determined for 60 strains r epresenting all nine species in the family Chlamydiaceae and for the relate d Chlamydiales species, Parachlamydia acanthamoebae and Simkania negevensis . These sequences were used to infer evolutionary relationships among the C hlamydiaceae. The analysis separated Chlamydophila and Chlamydia into two l ineages, with Chlamydophila forming three distinct clusters: the Chlamydoph ila pneumoniae strains; the Chlamydophila pecorum strains; and a third clus ter comprising the species Chlamydophila psittaci, Chlamydophila abortus, C hlamydophila caviae and Chlamydophila felis. The Chlamydia line of descent contained two clusters, with the Chlamydia suis strains distinctly separate d from strains of Chlamydia trachomatis and Chlamydia muridarum. This analy sis indicated that the rnpB sequence and structure are distinctive markers for species in the Chlamydiaceae. It was also demonstrated that the RNase P RNA derived from Chlamydia trachomatis is able to cleave a tRNA precursor in the absence of protein. These findings are discussed in relation to the structure of Chlamydia RNase P RNA.