The mechanism of phenotypically altered SM resistance in mutants of Escherichia coli JC5455 (Rldrd-19Km-) lrs and JC5455 (pON5300) was compared with that of the standard strain JC5455 (Rldrd-19Km-). On analyzing the membrane polypeptides in polyacrylamide gel both mutants were found to possess a protein spectrum different from that of ths standard strain. Transport of D-xylose and L-arginine was the same in all strains, transport of L-proline was decreased in JC5455 (pON5300) which may indicate a mutational interference with energy metabolism. The basic uptake of dihydrostreptomycin was the same in all strains but there were differences after preincubation of cells with streptomycin or glucose. The increased resistance of JC5455 (Rldrd-19Km-) lrs may be due to observed quantitative differences in membrane polypeptides that might play a role in the binding and functional expression of aminoglycoside-3'adenylyl transferase which modifies streptomycin. The increased sensitivity toward streptomycin in JC5455 (pON5300) can be explained by a mutation due to N-methyl-N'-nitro-N-nitrosoguanidine in the host cell since this change of sensitivity to streptomycin could not be transferred by transformation into a nonmutagenized strain. The coincidence of inducibility of increased transport of streptomycin by this antibiotic and the altered frequency of reversion to high levels of streptomycin resistance in JC5455 (pON5300) and in the transformant JC5455 (pON5302) may indicate that the altered reversibility toward phenotypically high resistance to streptomycin is a property of pON5300 and is transferred by transformation.

• MeSH
• antibiotická rezistence MeSH
• bakteriální proteiny analýza   MeSH
• bakteriální transformace MeSH
• dihydrostreptomycin metabolismus   MeSH
• Escherichia coli účinky léků   genetika   metabolismus   MeSH
• membránové proteiny analýza   MeSH
• R-plasmidy * MeSH
• streptomycin farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• bakteriální proteiny MeSH
• dihydrostreptomycin MeSH
• membránové proteiny MeSH
• streptomycin MeSH

Some properties of streptomycin-resistant mutants of Escherichia coli were analyzed. In a R+ culture, the phenotype under study may be significantly selected at a frequency of 10(-5) on media with higher streptomycin level. The lrs mutation is present in the cells prior to the action of streptomycin and remains in the cells even after curing of the R1 plasmid. The mapping of the lrs gene by conjugation with a concomitant transfer of chromosome and the R1 plasmid in different Hfr strains of E. coli failed to establish the localization of this gene in the tested chromosome regions. The presence of a cryptic plasmid was detected in cells with the lrs mutation after curing of the R1 plasmid. This plasmid codes neither fertility functions nor chloramphenicol-acetyltransferase, streptomycin-adenyltransferase, or ampicillin-beta-lactamase.

• MeSH
• antibiotická rezistence MeSH
• Escherichia coli účinky léků   enzymologie   genetika   MeSH
• mapování chromozomů * MeSH
• mutace MeSH
• R-plasmidy * MeSH
• streptomycin farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• streptomycin MeSH