title: [3H] dihydrostreptomycin accumulation and binding to ribosomes in Rhizobium mutants with different levels of streptomycin resistance.
abstract: Rhizobium trifolii B1, a symbiotic nitrogen fixer, is sensitive to streptomycin (10 microgram/ml) and spontaneously produces spheroplast-like forms during cultivation. Streptomycin-resistant mutants selected with high doses of antibiotic (1,000 microgram/ml) showed pleiotropic changes, including loss of spheroplast formation and infectivity to plants, whereas mutants selected with low doses of streptomycin (10 to 100 microgram/ml) retained properties of parent strain B1 (I. Zelazna-Kowalska, Acta Microbiol. Pol., in press). The present studies revealed that strain B1 and its mutant with a high level of streptomycin resistance, B1 strH, accumulated the antibiotic at similar rates. Mutant B1 strL, with a low level of streptomycin resistance (up to 100 microgram/ml), accumulated the antibiotic at a lower rate. Ribosomes isolated from strains B1 and B2 strL bound [3H]dihydrostreptomycin, whereas those from strain B1 strH did not. These observations indicate that, in R. trifolii B1, mutation to a high level of streptomycin resistance affects ribosomal structure, whereas low-level resistance involves a change in membrane permeability.
mesh_terms: D002463:Cell Membrane Permeability; D002701:Chloramphenicol / Q000494:pharmacology; D004096:Dihydrostreptomycin Sulfate / Q000378:metabolism*; D004352:Drug Resistance, Microbial; D009154:Mutation; D011485:Protein Binding; D012231:Rhizobium / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D013307:Streptomycin / Q000494:pharmacology*
chemical_list: D002701:Chloramphenicol; D004096:Dihydrostreptomycin Sulfate; D013307:Streptomycin