A SPONTANEOUS POINT MUTATION IN THE SINGLE 23S RIBOSOMAL-RNA GENE OF THE THERMOPHILIC ARCHAEON SULFOLOBUS-ACIDOCALDARIUS CONFERS MULTIPLE-DRUG RESISTANCE

Development of transformable vectors for thermophilic archaea requires the characterization of appropriate selectable marker genes. Many ant ibiotic inhibitors of protein biosynthesis are known to bind to rRNA; therefore, we screened 14 for their capacity to inhibit growth of the thermophilic archaeon Sulfolobus acidocaldarius. Carbomycin, celestice tin, chloramphenicol, puromycin, sparsomycin, tetracycline, and thiost repton all inhibited growth by different degrees. Spontaneous drug-res istant mutants were isolated from plates containing celesticetin or ch loramphenicol. Six mutants from each plate exhibited a C-2585-to-U tra nsition in the peptidyl transferase loop of 238 rRNA (corresponding to C-2452 in Escherichia coli 238 rRNA). The single-site mutation also c onferred resistance to carbomycin. The mutated 238 rRNA gene provides a potentially useful and dominant marker for a thermophilic archaeal v ector.