A Mutation in the 16S rRNA Decoding Region Attenuates the Virulence of Mycobacterium tuberculosis.

Mycobacterium tuberculosis contains a single rRNA operon that encodes targets for antituberculosis agents, including kanamycin. To date, only four mutations in the kanamycin binding sites of 16S rRNA have been reported in kanamycin-resistant clinical isolates. We hypothesized that another mutation(s) in the region may dramatically decrease M. tuberculosis viability and virulence. Here, we describe an rRNA mutation, U1406A, which was generated in vitro and confers resistance to kanamycin while highly attenuating M. tuberculosis virulence. The mutant showed decreased expression of 20% (n = 361) of mycobacterial proteins, including central metabolic enzymes, mycolic acid biosynthesis enzymes, and virulence factors such as antigen 85 complexes and ESAT-6. The mutation also induced three proteins, including KsgA (Rv1010; 16S rRNA adenine dimethyltransferase), which closely bind to the U1406A mutation site on the ribosome; these proteins were associated with ribosome maturation and translation initiation processes. The mutant showed an increase in 17S rRNA (precursor 16S rRNA) and a decrease in the ratio of 30S subunits to the 70S ribosomes, suggesting that the U1406A mutation in 16S rRNA attenuated M. tuberculosis virulence by affecting these processes.