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Mobilization of the Proteus mirabilis chromosome by R plasmid R772
Abstract:
The P-1 incompatibility group plasmid R772 can mobilize the chromosome of Proteus mirabilis strain PM5006. The decreasing gradient of recombinant recovery frequencies found for markers which were increasingly distal to 0 min with plasmid D donors was not found with R772. Instead, it produced recombinants for all markers at frequencies of about 5 X 10(-5) per donor. This is about 10-fold lower than the plasmid transfer frequency. Recombinants were stable and recombination was only detected over short segments of the chromosome which corresponded to about 10 min on the D plasmid map of the chromosome. All recombinants had inherited R772 and expressed all properties of the plasmid. Attempts to isolate variant plasmids with increased frequencies of recombinant formation were unsuccessful.
Insights
The R772 plasmid mobilizes the Proteus mirabilis chromosome, unlike plasmid D. It facilitates stable chromosomal recombination across specific segments, though at lower frequencies than plasmid transfer.
Area of Science:
- Microbiology
- Bacteriology
- Genetics
Background:
- Plasmid R772, belonging to the P-1 incompatibility group, is known to interact with bacterial chromosomes.
- Previous studies with plasmid D in Proteus mirabilis showed a gradient of recombinant recovery frequencies based on chromosomal marker distance.
Purpose of the Study:
- To investigate the chromosomal mobilization capabilities of plasmid R772 in Proteus mirabilis strain PM5006.
- To compare the recombination patterns generated by R772 with those previously observed with plasmid D.
Main Methods:
- Conjugation experiments were performed using Proteus mirabilis strain PM5006 with plasmid R772 as the donor.
- Recombinant recovery frequencies for various chromosomal markers were analyzed.
- Plasmid transfer frequencies and characteristics of the resulting recombinants were assessed.
Main Results:
- Plasmid R772 mobilized the Proteus mirabilis chromosome, producing stable recombinants.
- Unlike plasmid D, R772 did not exhibit a decreasing gradient of recombinant recovery frequencies for distal markers.
- Recombination occurred over short chromosomal segments (approx. 10 min on the D plasmid map) at frequencies of ~5 x 10(-5) per donor, approximately 10-fold lower than plasmid transfer frequency.
- All recombinants stably inherited and expressed the properties of R772.
Conclusions:
- Plasmid R772 is capable of chromosomal mobilization and recombination in Proteus mirabilis.
- The recombination mechanism mediated by R772 differs from that of plasmid D, showing a uniform recovery frequency across markers.
- Further attempts to enhance recombinant formation frequencies through plasmid variants were unsuccessful.