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Transposition of bacteriophage Mu in the Legionnaires disease bacterium
Abstract:
Legionnaires disease is an acute respiratory disease that is often fatal for immunocompromised patients. The causative agent of this disease, Legionella pneumophila, is a Gram-negative bacterium that is present in a variety of aquatic environments. L. pneumophila is a facultative intracellular parasite; it grows within human phagocytic cells and eventually causes their destruction. In contrast to many other intracellular parasites, L. pneumophila is a Gram-negative bacterium that can be grown in standard microbiological culture medium. To determine the factors that enable this organism to enter, survive, and multiply within human mononuclear phagocytes, we chose bacteriophage Mu, a powerful genetic tool that transposes within the host cell genome, to generate insertion mutations and gene fusions in the Legionella genome. Certain derivatives of Mu are able to generate fusions between target genes and the lac operon from Escherichia coli. We have determined that although Mu is unable to attach to L. pneumophila or complete its life cycle within Legionella, it does transpose within the Legionella genome. Transposition was detected with a mini-Mu phage that carries the lac operon of E. coli.
Insights
Researchers used bacteriophage Mu to study Legionella pneumophila, a bacterium causing Legionnaires disease. Despite challenges, Mu successfully transposed within Legionella, enabling genetic analysis of this pathogen.
Area of Science:
- Microbiology
- Bacteriology
- Molecular Genetics
Background:
- Legionnaires disease, caused by Legionella pneumophila, is a severe respiratory illness particularly dangerous for immunocompromised individuals.
- Legionella pneumophila is an intracellular parasite that infects human phagocytic cells, leading to cell destruction.
- Unlike many intracellular pathogens, L. pneumophila can be cultured in standard laboratory media, facilitating genetic studies.
Purpose of the Study:
- To identify factors enabling Legionella pneumophila entry, survival, and multiplication within human mononuclear phagocytes.
- To utilize bacteriophage Mu as a genetic tool for generating insertion mutations and gene fusions in the Legionella genome.
Main Methods:
- Employing bacteriophage Mu, a transposon-based genetic tool, to induce mutations and gene fusions in Legionella.
- Utilizing mini-Mu phage derivatives containing the Escherichia coli lac operon to detect transposition events.
- Assessing the ability of bacteriophage Mu to transpose within the Legionella genome, despite inability to attach or replicate.
Main Results:
- Bacteriophage Mu, while unable to attach to or complete its life cycle within Legionella pneumophila, was confirmed to transpose within the Legionella genome.
- Transposition events were successfully detected using a mini-Mu phage engineered with the E. coli lac operon.
Conclusions:
- Bacteriophage Mu transposition serves as a viable method for generating genetic modifications in Legionella pneumophila.
- This approach enables the study of Legionella virulence factors and host-pathogen interactions, crucial for understanding Legionnaires disease pathogenesis.