Cloning and characterization of the rRNA genes and flanking regions from Babesia bovis: use of the genes as strain discriminating probes.

Three sets of rRNA genes (units 1S-3S) have been identified in Babesia bovis (Samford isolate). All three units are present in the same, probably single, copy number. The rRNA genes and flanking regions have been analysed by cloning, restriction mapping and DNA hybridization. The units are approximately 7 kb in length and have essentially identical restriction maps. In contrast the flanking regions exhibit significant restriction site differences. However, the regions upstream of all three units are related and sequences similar to part of the region upstream of units 1S and 3S are present in multiple copies in the genome. The downstream regions appear to be unrelated, but downstream from unit 1S is a region of at least 7 kb similar to a second region not closely linked to the rDNA units. The restriction enzyme site polymorphisms in the flanking regions of the equivalent units in different isolates allow ready discrimination among six different isolates of B. bovis.