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Fate of germinated Bacillus anthracis spores in primary murine macrophages
C Guidi-Rontani1, M Levy, H Ohayon
1Unité Toxines et Pathogénie Bactériennes, CNRS URA 2172, and Station Centrale de Microscopie Electronique, Institut Pasteur, 28 rue du Dr Roux, 75015 Paris, France. rontani@pasteur.fr
Abstract:
We investigated the fate of germinated Bacillus anthracis spores after their germination in Swiss murine peritoneal macrophages and in the cell line RAW264.7. We found that the lethal toxin and the oedema toxin are germ-associated factors that are essential for the survival of the vegetative form in host cells. We also found that pX02 is not involved in this complex pathogenic process. By transmission electron microscopy, we showed the tight interaction between the exosporium of the spore and the phagosomal membrane of the macrophage. Our data strongly suggest that the B. anthracis toxinogenic, unencapsulated Sterne strain (7702) does not multiply within macrophages. These results contributed to reveal the strategies used by B. anthracis to survive within the host and to reach the external medium where they proliferate.
Insights
Bacillus anthracis toxins are crucial for vegetative cell survival within host macrophages. The Sterne strain (7702) does not multiply inside these cells, revealing bacterial survival strategies.
Area of Science:
- Microbiology
- Immunology
- Pathogenesis
Background:
- Bacillus anthracis spores germinate into vegetative cells within host macrophages.
- Understanding the intracellular survival mechanisms of B. anthracis is critical for developing effective treatments.
Purpose of the Study:
- To investigate the fate of germinated Bacillus anthracis spores within macrophages.
- To identify factors essential for vegetative B. anthracis survival in host cells.
Main Methods:
- In vitro infection of Swiss murine peritoneal macrophages and RAW264.7 cell line with B. anthracis.
- Transmission electron microscopy (TEM) to visualize spore-macrophage interactions.
- Analysis of toxin involvement and bacterial multiplication.
Main Results:
- Germination-associated factors, lethal toxin and oedema toxin, are essential for vegetative B. anthracis survival in host cells.
- The pX02 plasmid is not implicated in this intracellular pathogenic process.
- TEM revealed intimate interaction between the spore exosporium and the macrophage phagosomal membrane.
- The toxinogenic, unencapsulated Sterne strain (7702) did not multiply within macrophages.
Conclusions:
- B. anthracis utilizes specific toxins for survival within host macrophages.
- The Sterne strain's inability to multiply intracellularly highlights distinct survival strategies.
- These findings elucidate mechanisms of B. anthracis host cell interaction and dissemination.