RNase III Processing of rRNA in the Lyme Disease SpirocheteBorrelia burgdorferi
ABSTRACTThe rRNA genes ofBorrelia(Borreliella)burgdorferiare unusually organized; the spirochete has a single 16S rRNA gene that is more than 3 kb from a tandem pair of 23S-5S rRNA operons. We generated anrncnull mutant inB. burgdorferithat exhibits a pleiotropic phenotype, including decreased growth rate and increased cell length. Here, we demonstrate that endoribonuclease III (RNase III) is, as expected, involved in processing the 23S rRNA inB. burgdorferi. The 5′ and 3′ ends of the three rRNAs were determined in the wild type andrncBbmutants; the results suggest that RNase III inB. burgdorferiis required for the full maturation of the 23S rRNA but not for the 5S rRNA nor, curiously, for the 16S rRNA.IMPORTANCELyme disease, the most common tick-borne zoonosis in the Northern Hemisphere, is caused by the bacteriumBorrelia(Borreliella)burgdorferi, a member of the deeply branching spirochete phylum.B. burgdorfericarries a limited suite of ribonucleases, enzymes that cleave RNA during processing and degradation. Several ribonucleases, including RNase III, are involved in the production of ribosomes, which catalyze translation and are a major target of antibiotics. This is the first study to dissect the role of an RNase in any spirochete. We demonstrate that an RNase III mutant is viable but has altered processing of rRNA.