Related Experiment Videos
Growth of recombinant Mycobacterium tuberculosis H37Ra in mouse macrophages
1Department of Clinical Biological Sciences, University of Pavia, Varese, Italy.
Abstract:
Mycobacterium tuberculosis H37Rv and H37Ra were derived from the same parental strain but differ strikingly in their virulence for experimental animals. Transfer of genetic material between these closely related strains resulted in the isolation of a number of recombinant H37Ra clones bearing the in vivo growth-promoting ivg locus of H37Rv. The recombinant strain was phagocytosed by murine peritoneal macrophages infected in vivo or in vitro and their intracellular growth rates were compared with the vector control. The intracellular growth of the recombinant was significantly faster than the vector control, but substantially slower than the wild-type H37Rv control, regardless of the method used to infect the macrophages. The slower intracellular growth observed for the recombinant strains was not due to a genetically induced metabolic defect, since they grew in synthetic liquid medium at rates equal to those observed for both H37Rv and H37Ra. Peritoneal macrophage monolayers provide a rapid and convenient assay by which to screen H37Ra recombinants for the presence of putative virulence genes.
Insights
Researchers transferred a virulence gene locus from Mycobacterium tuberculosis H37Rv to H37Ra. The resulting recombinant strain showed enhanced intracellular growth in macrophages, indicating a key factor in tuberculosis virulence.
Area of Science:
- Microbiology
- Genetics
- Immunology
Background:
- Mycobacterium tuberculosis strains H37Rv and H37Ra exhibit significant differences in virulence.
- Understanding the genetic basis of virulence is crucial for combating tuberculosis.
Purpose of the Study:
- To investigate the role of the ivg locus in Mycobacterium tuberculosis virulence.
- To characterize the intracellular growth of recombinant H37Ra strains in macrophages.
Main Methods:
- Genetic transfer of the ivg locus from H37Rv to H37Ra.
- Infection of murine peritoneal macrophages with recombinant and control strains.
- Assessment of intracellular growth rates in macrophages.
Main Results:
- Recombinant H37Ra strains with the H37Rv ivg locus demonstrated significantly faster intracellular growth compared to vector controls.
- Intracellular growth of recombinants was slower than wild-type H37Rv.
- Recombinant strains exhibited normal growth rates in liquid culture, ruling out general metabolic defects.
Conclusions:
- The ivg locus of H37Rv contributes to enhanced intracellular growth in Mycobacterium tuberculosis.
- Murine peritoneal macrophage monolayers serve as an effective model for screening virulence genes in H37Ra recombinants.
- This study provides insights into the genetic determinants of M. tuberculosis virulence.