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Construction and physical mapping of plasmids containing the MetA gene of Escherichia coli K-12
Abstract:
Plasmids containing the metA gene of E. coli K-12 were constructed in vitro using pBR322 as the cloning vehicle and lambda metA transducing phage as the source of metA DNA. EcoRI digests of pBR322 and lambda metA20 were joined by ligase and plasmids carrying the metA gene were selected after transformation in a metA deletion strain. Recombinant DNA molecules contained one pBR322 fragment and one lambda metA20 fragment of 12.2 kb which was present in either of two possible orientations. Plasmids constructed by BamHI digestion of lambda metA2 contained a single bacterial DNA fragment of 5.8 kb inserted in the tet gene. Insertion of the metA fragment led to loss of resistance to tetracycline in one orientation and partial resistance in the opposite orientation.
Insights
Researchers cloned the metA gene from E. coli into plasmids using molecular techniques. This gene is essential for methionine biosynthesis and its insertion affected antibiotic resistance.
Area of Science:
- Molecular Biology
- Microbial Genetics
- Recombinant DNA Technology
Background:
- The metA gene in Escherichia coli K-12 is crucial for methionine biosynthesis.
- Understanding gene function often involves cloning and expressing genes in model systems.
- Plasmids serve as versatile vectors for gene manipulation and cloning.
Purpose of the Study:
- To construct recombinant plasmids containing the metA gene from E. coli K-12.
- To investigate the expression and functional characteristics of the cloned metA gene.
- To analyze the impact of metA gene insertion on plasmid properties.
Main Methods:
- In vitro construction of plasmids using pBR322 as a cloning vehicle.
- Utilizing lambda metA transducing phage as the source of metA DNA.
- Restriction enzyme digestion (EcoRI, BamHI) and DNA ligation.
- Transformation of a metA deletion strain of E. coli.
- Selection of recombinant plasmids and analysis of antibiotic resistance markers.
Main Results:
- Recombinant plasmids carrying the E. coli metA gene were successfully constructed.
- The metA gene fragment was identified as 12.2 kb (EcoRI) or 5.8 kb (BamHI).
- Insertion of the metA fragment into the tetracycline resistance gene of pBR322 resulted in altered resistance phenotypes.
- Two orientations of the 12.2 kb fragment were observed in the recombinant DNA molecules.
Conclusions:
- The metA gene of E. coli K-12 can be successfully cloned and expressed using pBR322.
- The cloned metA gene influences the tetracycline resistance of the pBR322 vector.
- This study provides a foundation for further functional analysis of the metA gene.