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Cloning of chromosomal genes in Streptococcus pneumoniae
Abstract:
A system for molecular cloning in Streptococcus pneumoniae was developed. The multicopy plasmids pMV158 (5.4 kilobases) and pLS1 (4.3 kilobases), which confer tetracycline resistance, were used as vectors to clone chromosomal genes of S. pneumoniae in host cells of this species. A 3.3-kilobase restriction fragment containing the malM gene, which codes for amylomaltase, was cloned in a deletion mutant lacking chromosomal homology with the fragment. The recombinant plasmid pLS70, could transform over 50% of a recipient population to maltose utilization. Amylomaltase constituted up to 10% of the protein of cells containing pLS70. A derivative with a deletion, pLS69, appeared to gain a selective advantage by producing less enzyme. A 10-kilobase restriction fragment containing the sul-d gene for sulfonamide resistance was cloned in the presence of the homologous chromosomal gene. De novo establishment of a recombinant plasmid was just as frequent as transformation in an endogenous plasmid. Despite the processing of DNA during uptake in the transformation of S. pneumoniae, recombinant plasmids can be introduced. Models for the reconstruction of recombinant DNA in cells of S. pneumoniae and Bacillus subtilis are considered and compared.
Insights
A new molecular cloning system for Streptococcus pneumoniae enables the introduction of foreign genes. This facilitates the study of bacterial genetics and the development of novel biotechnological applications.
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- Streptococcus pneumoniae is a significant human pathogen.
- Efficient molecular cloning systems are crucial for genetic manipulation and research in S. pneumoniae.
Purpose of the Study:
- To develop and characterize a novel system for molecular cloning in Streptococcus pneumoniae.
- To demonstrate the feasibility of introducing and expressing cloned genes in S. pneumoniae.
Main Methods:
- Utilized multicopy plasmids (pMV158, pLS1) as vectors for cloning chromosomal genes.
- Cloned the malM gene (amylomaltase) and the sul-d gene (sulfonamide resistance) into S. pneumoniae.
- Assessed transformation efficiency and protein expression of recombinant plasmids.
Main Results:
- Successfully cloned and expressed the malM gene, leading to maltose utilization in over 50% of recipient cells.
- Amylomaltase constituted up to 10% of cellular protein in cells containing the recombinant plasmid pLS70.
- Cloned the sul-d gene, demonstrating successful introduction of recombinant plasmids even with homologous chromosomal genes present.
Conclusions:
- Established a functional molecular cloning system for Streptococcus pneumoniae.
- Demonstrated the utility of this system for studying gene function and developing genetic tools.
- The findings have implications for genetic engineering and understanding DNA manipulation in Gram-positive bacteria.