Bacteriophage lambda
Bacteriophage λ is the archetype of the lambdoid, or lambda-like phage, a subclass of the siphoviridae. λ is a temperate phage.
Morphology
The λ phage has an icosahedral head about 50 nm in diameter, and a flexible tail about 150nm long.[1] The head contains a single double-stranded DNA molecule about 48 kb in length; by weight the genome is about 32x106 Da and comprises about half of the phage's weight.[1] The DNA is linear when packaged, and recircularizes at the cos (cohesive end site) once injected into the host. [1]
Genome Organization
Life Cycle
Lytic Cycle
The lytic cycle is the usual life cycle, and results in the death of the host bacteria.
Adsorbtion and Injection
The tip of the phage tail (J protein) attaches to the host cell protein lamB, which is displayed on the outer membrane.[1] The dsDNA is injected through the tail as a linear genome, when the phage tail interacts with the inner membrane protein ptsM and recircularizes once inside the host due to complementary 12nt long sticky ends. [1]
Early Gene Expression
The cro gene is an immediate-early gene product.[2] CII and CIII are delayed-early gene products. [2]
Middle Gene Expression
DNA Replication
Late Gene Expression
Packaging
Lysis
Lysogenic State
The lysogenic lifecycle is the result of integration of the λ DNA into the host genome, and does not result in the death of the host cell. The λ DNA/host DNA unit is termed a prophage. The λ DNA is integrated at the attP (for attachment phage) and the attB (for attachment bacteria) loci.[2]
Lysis-Lysogeny Switch
Prophage Induction
See also
- Gene List
- Enterobacteriophage lambda at the NCBI taxonomy browser
- wikipedia: Lambda_phage
- ICTVdb entry
- Siphoviridae at MicrobeWiki
- Phage lambda on UniProt
References
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