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DNA injection during bacteriophage T4 infection of Escherichia coli
Abstract:
The process of phage T4 DNA injection into the host cell was studied under a fluorescent microscope, using 4',6-diamidino-2-phenylindole as a DNA-specific fluorochrome. The phage DNA injection was observed when spheroplasts were infected with the artificially contracted phage particles having a protruding core. The DNA injection was mediated by the interaction of the core tip with the cytoplasmic membrane of the spheroplast. A membrane potential was not required for the process of DNA injection. On the other hand, DNA injection upon infection by intact noncontracted phage of the intact host cell was inhibited by an energy poison. Based on these observations, together with results from previous work, a model for the T4 infection process is presented, and the role of the membrane potential in the infection process is discussed.
Insights
Bacteriophage T4 injects its DNA into host cells via its core tip interacting with the cell membrane. This DNA injection process does not require a membrane potential, challenging previous models of T4 infection.
Area of Science:
- Microbiology
- Molecular Biology
- Virology
Background:
- Bacteriophage T4 is a model organism for studying DNA injection mechanisms.
- The precise steps and energy requirements for T4 DNA injection into host cells remain incompletely understood.
Purpose of the Study:
- To elucidate the mechanism of T4 phage DNA injection.
- To investigate the role of membrane potential in the T4 DNA injection process.
Main Methods:
- Fluorescence microscopy was employed to visualize T4 DNA injection.
- 4',6-diamidino-2-phenylindole (DAPI) was used as a DNA-specific fluorochrome.
- Infection experiments were conducted using both artificially contracted phage particles and intact phage with host spheroplasts and intact host cells.
Main Results:
- T4 DNA injection was observed using artificially contracted phage particles with protruding cores interacting with spheroplast membranes.
- The DNA injection process was mediated by the core tip's interaction with the cytoplasmic membrane.
- A membrane potential was not necessary for DNA injection in spheroplasts.
- DNA injection into intact host cells by noncontracted phage was inhibited by an energy poison.
Conclusions:
- A model for T4 infection is proposed, highlighting the core tip-membrane interaction as the primary mechanism for DNA injection.
- The findings suggest that membrane potential is not a prerequisite for T4 DNA injection, particularly in simplified systems like spheroplasts.