Genetic relationships among the members of the family rickettsiaceae as shown by DNA restriction fragment polymorphism analysis.

The genetic diversity of members of the genus Rickettsia was examined using restriction site polymorphisms found within a series of DNA fragments scattered throughout the genome. Rickettsia belli, R. akari, and R. australis were the most divergent species when compared to the other species examined. These three species were also not closely related to each other. The other examined species were more tightly clustered. This survey also examined the genetic diversity within several species. The unexpected finding of this survey is that several species of rickettsia are as closely related to the surveyed strains of R. rickettsii as these strains are to each other. These results indicate that R. sibirica, R. parkeri, R. rickettsii, and an unnamed isolate from Africa are likely to be strains of a single rickettsial species of worldwide distribution. R. conorii was very closely related to this R. rickettsii-containing group but is likely to remain in a genetically distinct category as the data base expands.