A CHIMERIC DISPOSITION OF THE ELONGATION-FACTOR GENES IN RICKETTSIA-PROWAZEKII

An exceptional disposition of the elongation factor genes is observed in Rickettsia prowazekii, in which there is only one tuf gene, which i s distant from the lone firs gene, In contrast, the closely related ba cterium Agrobacterium tumefaciens has the normal bacterial arrangement of two tuf genes, of which one is tightly linked to the fus gene. Ana lysis of the flanking sequences of the single tuf gene in R. prowazeki i shows that it is preceded by two of the four tRNA genes located in t he 5' region of the Escherichia coli tufB gene and that it is followed by rpsJ as well as associated ribosomal protein genes, which in E. co li are located downstream of the tufA gene, The fus gene is located wi thin the str operon and is followed by one tRNA gene as well as by the genes secE and nusG, which are located in the 3' region of tufB in E. coli, This atypical disposition of genes suggests that intrachromosom al recombination between duplicated tuf genes has contributed to the e volution of the unique genomic architecture of R. prowazekii.