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Suppression of the formation of polygenotypic recombinant colonies by a maf mutation in mating with HfrH
Abstract:
W3011, a Cavalli-type Hfr (HfrC), was mated with F-KY9474, maf-1, which cannot maintain F or F-like plasmids, and with F-OU9474, Maf+, a spontaneous revertant of KY9474. The recombinant colonies obtained were 100% monogenotypic from KY9474 and 90% monogenotypic from OU9474. On the other hand, in matings with OU11, a Hayes-type Hfr (HfrH), and these two F- strains, recombinant colonies derived from KY9474 showed only 22% polygenotypic recombinant colonies; whereas, those derived from OU9474 showed a high production rate (57%) of polygenotypic recombinant colonies. Among the polygenotypic recombinant colonies derived from KY9474 maf-1, 50% contained three or more recombinant types. These were probably derived from a small fraction of Maf+ revertants in the KY9474 population, as suggested by the results of mating this strain with M80, an F' strain that contains an amber mutation in traH. These results support the hypothesis that the donor DNA fragments derived from an HfrH can undergo a limited replication in the recipient to produce polygenotypic recombinant colonies, whereas those derived from HfrC cannot.
Insights
Donor DNA fragments from HfrH strains can replicate in recipients, forming polygenotypic recombinant colonies. Donor DNA from HfrC strains cannot replicate, resulting in monogenotypic colonies, differentiating Hfr types in bacterial conjugation.
Area of Science:
- Bacterial genetics
- Molecular biology
- Microbiology
Background:
- Conjugation is a key mechanism for genetic exchange in bacteria.
- High-frequency recombination (Hfr) strains are crucial tools for mapping bacterial genomes.
- Different Hfr strains (e.g., HfrC, HfrH) exhibit distinct transfer patterns and recombination outcomes.
Purpose of the Study:
- To investigate the replication potential of donor DNA fragments in bacterial recipients during conjugation.
- To differentiate between Cavalli-type (HfrC) and Hayes-type (HfrH) Hfr strains based on recombinant colony genotypy.
- To elucidate the mechanisms underlying the formation of monogenotypic versus polygenotypic recombinant colonies.
Main Methods:
- Bacterial conjugation experiments were performed using different Hfr donor strains (HfrC, HfrH) and F- recipient strains (maf-1 and Maf+ revertants).
- Recombinant colonies were analyzed for their genotypic uniformity (monogenotypic vs. polygenotypic).
- Analysis included mating with an F' strain carrying a specific mutation to assess revertant populations.
Main Results:
- Mating HfrC with F- strains yielded predominantly monogenotypic recombinant colonies.
- Mating HfrH with F- strains resulted in a significant proportion of polygenotypic recombinant colonies.
- Polygenotypic recombinants from HfrH matings indicated limited replication of donor DNA fragments in the recipient.
Conclusions:
- Donor DNA fragments from HfrH strains can undergo limited replication in recipients, leading to polygenotypic recombinant colonies.
- Donor DNA fragments from HfrC strains do not appear to replicate in recipients, producing monogenotypic colonies.
- These findings support a model distinguishing HfrH and HfrC behavior based on DNA replication dynamics during conjugation.