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Penetration of Bdellovibrio bacteriovorus into host cells
Abstract:
Electron microscopy reveals that, in Bdellovibrio infection, after the formation of a passage pore in the host cell wall, the differentiated parasite penetration pole is associated with the host protoplast. This firm contact persists throughout the parasite penetration and after this process is completed. In penetrated hosts this contact is also apparent by phase microscopy. The association between the walls of the parasite and the host at the passage pore, on the other hand, is transient. Bdellovibrio do not penetrate hosts whose protoplast and cell walls are separated by plasmolysis, or in which the membrane-wall relationship is affected by low turgor pressure. It is concluded, therefore, that for penetration to occur it is essential that the host protoplast be within reach of the parasite, so that a firm contact can be established between them. A penetration mechanism is proposed that is effected by forces generated by fluxes of water and solutes due to structural changes in the infected host envelope. These forces cause a differential expansion of the host protoplast and cell wall and their separation from each other around the entry site, while the parasite remains firmly anchored to the host protoplast. Consequently, the parasite ends up enclosed in the expanded host periplasm. The actual entry, therefore, is a passive act of the parasite.
Insights
Bdellovibrio bacteria penetrate host cells by anchoring to the host protoplast, not the cell wall. This firm attachment, essential for invasion, involves forces from water and solute fluxes, making parasite entry passive.
Area of Science:
- Microbiology
- Cell Biology
- Bacteriology
Background:
- Bdellovibrio are predatory bacteria that infect other Gram-negative bacteria.
- Understanding the mechanism of Bdellovibrio host cell penetration is crucial for microbial pathogenesis research.
Purpose of the Study:
- To elucidate the physical interactions and forces involved in Bdellovibrio host cell penetration.
- To propose a mechanism for how Bdellovibrio enters its host cell.
Main Methods:
- Utilized electron microscopy to observe Bdellovibrio-host interactions during infection.
- Employed phase microscopy to visualize parasite-host contact in penetrated cells.
Main Results:
- Bdellovibrio establishes firm, persistent contact with the host protoplast, not the cell wall, during and after penetration.
- Penetration is inhibited in hosts with plasmolysis or low turgor pressure, indicating the importance of protoplast proximity.
- A mechanism involving water and solute fluxes causing differential expansion of the host envelope is proposed.
Conclusions:
- Host protoplast proximity and firm attachment are essential for Bdellovibrio penetration.
- Penetration involves forces generated by host envelope structural changes, leading to passive entry of the parasite into the expanded periplasm.