title: Mechanisms of streptomycin resistance: selection of mutations in the 16S rRNA gene conferring resistance.
abstract: Chromosomally acquired streptomycin resistance is frequently due to mutations in the gene encoding the ribosomal protein S12, rpsL. The presence of several rRNA operons (rrn) and a single rpsL gene in most bacterial genomes prohibits the isolation of streptomycin-resistant mutants in which resistance is mediated by mutations in the 16S rRNA gene (rrs). Three strains were constructed in this investigation: Mycobacterium smegmatis rrnB, M. smegmatis rpsL(3+), and M. smegmatis rrnB rpsL(3+). M. smegmatis rrnB carries a single functional rrn operon, i.e., rrnA (comprised of 16S, 23S, and 5S rRNA genes) and a single rpsL+ gene; M. smegmatis rpsL(3+) is characterized by the presence of two rrn operons (rrnA and rrnB) and three rpsL+ genes; and M. smegmatis rrnB rpsL(3+) carries a single functional rrn operon (rrnA) and three rpsL+ genes. By genetically altering the number of rpsL and rrs alleles in the bacterial genome, mutations in rrs conferring streptomycin resistance could be selected, as revealed by analysis of streptomycin-resistant derivatives of M. smegmatis rrnB rpsL(3+). Besides mutations well known to confer streptomycin resistance, novel streptomycin resistance conferring mutations were isolated. Most of the mutations were found to map to a functional pseudoknot structure within the 530 loop region of the 16S rRNA. One of the mutations observed, i.e., 524G-->C, severely distorts the interaction between nucleotides 524G and 507C, a Watson-Crick interaction which has been thought to be essential for ribosome function. The use of the single rRNA allelic M. smegmatis strain should help to elucidate the principles of ribosome-drug interactions.
authors.affiliation: Institut für Medizinische Mikrobiologie, Medizinische Hochschule Hannover, 30623 Hannover, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Springer
authors.forename: Y G
authors.initials: YG
authors.lastname: Kidan
authors.forename: T
authors.initials: T
authors.lastname: Prammananan
authors.forename: K
authors.initials: K
authors.lastname: Ellrott
authors.forename: E C
authors.initials: EC
authors.lastname: Böttger
authors.forename: P
authors.initials: P
authors.lastname: Sander
mesh_terms: D000483:Alleles; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D004269:DNA, Bacterial / Q000032:analysis; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D009154:Mutation; D020102:Mycobacterium smegmatis / Q000187:drug effects / Q000235:genetics*; D009690:Nucleic Acid Conformation; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics*; D013307:Streptomycin / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; D013307:Streptomycin