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High frequency transduction of R-factor encoded gentamicin resistance by bacteriophage P1Cm
Abstract:
No transposition of plasmid-coded gentamicin resistance from more than fifty different R-plasmids onto a deletion derivative of bacteriophage lambda was found. In contrast, 13 out of 17 R-plasmids gave rise to the formation of high frequency transducing (hft) hybrids of phage P1Cm. All the hft P1Cm derivatives transduced other antibiotic resistances in addition to gentamicin resistance. The DNA sequences found to be integrated in the prophage genomes of hft phages were generally longer than 15 kb, and ranged up to 60 kb. In most cases analyzed the points of insertions were close to the IS1 elements resident in P1Cm. In part of the hybrid phages the entire R-plasmids were cointegrated. One plasmid (pWP14a) cointegrated preferentially into a Bg1II fragment of P1Cm containing an invertible structure (C-loop). Eleven out of 16 R-plasmids showed homology to IS1.
Insights
Bacteriophage P1Cm efficiently transduced gentamicin resistance genes from R-plasmids, unlike bacteriophage lambda. These P1Cm hybrids integrated large DNA segments, often near IS1 elements, enabling co-transduction of multiple antibiotic resistances.
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- R-plasmids confer antibiotic resistance.
- Bacteriophages can mediate gene transfer.
Purpose of the Study:
- To investigate the transposition of plasmid-coded gentamicin resistance genes.
- To characterize the formation of hybrid phages capable of transducing antibiotic resistance.
Main Methods:
- Transposition assays using R-plasmids and bacteriophages lambda and P1Cm.
- Analysis of high frequency transducing (hft) hybrid phages.
- DNA sequencing and homology studies.
Main Results:
- Bacteriophage lambda showed no gentamicin resistance transposition.
- 13 out of 17 R-plasmids formed hft P1Cm hybrids.
- Hft P1Cm derivatives transduced multiple antibiotic resistances.
- Integrated DNA sequences ranged from 15 to 60 kb, often near IS1 elements.
- Some R-plasmids cointegrated entirely into P1Cm.
Conclusions:
- Bacteriophage P1Cm is highly effective in mediating the transfer of R-plasmid DNA.
- Transposition and cointegration events are associated with IS1 elements in R-plasmids and P1Cm.
- Hybrid phages facilitate the co-transduction of multiple antibiotic resistance genes.