Determination of genome sizes of Rickettsia spp. within the spotted fever group, using pulsed-field gel electrophoresis

The chromosome lengths of six spotted fever group Rickettsia species (Rickettsia rickettsii, R. conorii, R. rhipicephali, R. sibirica, R. australis, and R. akari) were estimated by pulsed-field gel electrophoresis. The genome size of R. rickettsii was about 2,100 kb, but the chromosome lengths of the five other species were, surprisingly, much lower and ranged between 1,200 and 1,300 kb.