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DNA repair in Proteus mirabilis. VI. Plasmid (R46-) mediated recovery and UV mutagenesis
Abstract:
The expression of plasmid R46-mediated recovery and mutagenic function (s) was studied in P. mirabilis, which is normally either weakly or non-mutable after UV exposure. The plasmid was found to confer on P. mirabilis enhanced UV resistance as well as UV-induced mutability for various types of forward mutations and reversion of the thr273 mutation. The plasmid enhanced survival of UV-irradiated phages in P. mirabilis both in unirradiated host cells and with increased efficiency after UV-exposure of host cells, as is characteristic of UV-inducible phage reactivation. Spontaneous mutability of P. mirabilis harboring R46 was about 2 to 7 times higher than that of cells without plasmid, depending on the marker, repair type, and plating density of the cells used. All of these R46-mediated rescue and mutagenic functions require the rec672 + gene function. It is assumed that the plasmid R46 adds functions to P. mirabilis comparable to those deficient in umuC and uvm mutants of E. coli (Kato and Shinoura, 1977; Steinborn, 1978) and that P. mirabilis possesses functions homologous to those controlled in E. coli by the recA + and lexA + genes. The significance of plasmid-mediated rescue and mutagenic functions for bacteria which lack the misrepair branch of mutagenesis, is discussed.
Insights
Plasmid R46 enhances UV resistance and mutation rates in P. mirabilis, conferring functions similar to E. coli
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- P. mirabilis exhibits limited mutability after UV exposure.
- Plasmid R46's role in bacterial DNA repair and mutagenesis is not fully understood.
Purpose of the Study:
- To investigate the recovery and mutagenic functions of plasmid R46 in P. mirabilis.
- To determine if plasmid R46 confers UV resistance and UV-induced mutability to P. mirabilis.
Main Methods:
- Studied plasmid R46 expression in P. mirabilis.
- Assessed UV resistance and UV-induced mutability.
- Examined phage survival after UV irradiation in P. mirabilis.
- Investigated spontaneous mutability in P. mirabilis with and without plasmid R46.
Main Results:
- Plasmid R46 significantly enhanced UV resistance and UV-induced mutability in P. mirabilis.
- The plasmid increased survival of UV-irradiated phages, indicating UV-inducible phage reactivation.
- Spontaneous mutability of P. mirabilis harboring R46 was 2 to 7 times higher than in cells without the plasmid.
- R46-mediated functions require the rec672+ gene and are comparable to E. coli umuC/uvm mutants.
Conclusions:
- Plasmid R46 confers significant mutagenic and recovery functions to P. mirabilis.
- These functions are dependent on the rec672+ gene.
- Plasmid R46 may provide P. mirabilis with repair mechanisms analogous to E. coli's recA+ and lexA+ genes.