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Efficient insertional mutagenesis in lactococci and other gram-positive bacteria
E Maguin1, H Prévost, S D Ehrlich
1Laboratoire de Génétique Microbienne, Institut National de la Recherche Agronomique, Domaine de Vilvert, Jouy en Josas, France.
Journal of Bacteriology
|February 1, 1996
Summary
Researchers developed a new transposon mutagenesis system using ISS1 and pG+ host for efficient gene study in Lactococcus lactis. This tool enables stable, food-grade mutant generation for fermentation applications.
Area of Science:
- Microbiology
- Molecular Biology
- Genetic Engineering
Background:
- Studying chromosomal genes in lactococci is challenging due to the absence of effective transposon mutagenesis systems.
- Existing methods are insufficient for poorly transformable strains, hindering genetic analysis.
Purpose of the Study:
- To develop a novel, efficient transposon mutagenesis tool for Lactococcus lactis and related bacteria.
- To enable random gene insertion and facilitate the study of gene function and regulation in industrially relevant microorganisms.
Main Methods:
- Integration of the insertion sequence ISS1 with a thermosensitive replicon (pG+ host) to create a mutagenic system.
- Application of the system in Lactococcus lactis, Enterococcus faecalis, and Streptococcus thermophilus to assess transposition efficiency and randomness.
- Utilizing the duplicated ISS1 flanking the plasmid for gene cloning and subsequent plasmid excision for stable mutant generation.
Main Results:
- Achieved high-frequency random transposition (approx. 1%) of ISS1 in Lactococcus lactis, enabling efficient mutagenesis.
- Demonstrated successful random insertion in various lactococcal strains, Enterococcus faecalis, and Streptococcus thermophilus.
- Developed a method for stable mutant generation with a single ISS1 copy and no foreign markers, suitable for food-grade applications.
Conclusions:
- The developed ISS1-based system provides an efficient and versatile tool for transposon mutagenesis in lactococci and other Gram-positive bacteria.
- This system overcomes limitations of previous methods, allowing for the creation of stable, food-grade mutants for use in fermentation.
- Facilitates genetic research and strain improvement in industrially important lactic acid bacteria.