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Organization of Methanobacterium thermoautotrophicum bacteriophage psi M1 DNA
M Jordan1, L Meile, T Leisinger
1Mikrobiologisches Institut, Eidgenössische Technische Hochschule, Zürich, Switzerland.
Abstract:
psi M1 is a virulent bacteriophage of Methanobacterium thermoautotrophicum strain Marburg. Restriction enzyme analysis of the linear, 30.4 kb phage DNA led to a circular map of the 27.1 kb psi M1 genome. psi M1 is thus circularly permuted and exhibits terminal redundancy of approximately 3 kb. Packaging of psi M1 DNA from a concatemeric precursor initiates at the pac site which was identified at coordinate 4.6 kb on the circular genome map. It proceeds clockwise for at least five packaging rounds. Headful packaging was also shown for psi M2, a phage variant with a 0.7 kb deletion at coordinate 23.25 on the map.
Insights
This study characterizes the psi M1 bacteriophage genome, revealing its circular permutation and terminal redundancy. DNA packaging initiates at a specific pac site, proceeding in a headful manner.
Area of Science:
- Microbiology
- Virology
- Genomics
Background:
- Methanobacterium thermoautotrophicum is an archaeon relevant to anaerobic environments.
- Bacteriophages are viruses that infect bacteria and archaea, playing roles in microbial evolution and ecology.
- Understanding phage genomics is crucial for molecular biology and biotechnology.
Purpose of the Study:
- To elucidate the genomic structure of the virulent bacteriophage psi M1.
- To identify key elements involved in psi M1 DNA packaging.
- To characterize genome packaging mechanisms in related phages.
Main Methods:
- Restriction enzyme analysis of phage DNA.
- Construction of a circular genome map.
- Identification of the pac site and analysis of DNA packaging directionality.
Main Results:
- The psi M1 genome is 27.1 kb and circularly permuted with ~3 kb terminal redundancy.
- A specific pac site at coordinate 4.6 kb was identified as the initiation point for DNA packaging.
- Headful packaging was confirmed, proceeding clockwise for multiple rounds.
- The psi M2 variant exhibits a deletion without affecting packaging.
Conclusions:
- psi M1 possesses a unique genome organization and packaging strategy.
- The identified pac site is essential for initiating the packaging of concatemeric DNA.
- Headful packaging is a conserved mechanism in related bacteriophages.