DNA polymorphism in the conserved 190 kDa antigen gene repeat region among spotted fever group Rickettsiae

The 190 kDa protein gene of R. rickettsii (R strain) contains a large region of tandemly arranged repeats. Homologous sequences were discovered within the genomes of all but one species of spotted fever group Rickettsiae. Southern blots showed restriction fragment length polymorphisms between species of Rickettsiae indicating structural differences among repeat regions. Further analysis using polymerase chain reaction techniques indicated the repeat regions vary in size among Rickettsiae. In addition, strains of R. rickettsii that vary in virulence were found to contain polymorphisms in this region.