Bacteriophage lambda: Difference between revisions
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==== DNA Replication ==== | ==== DNA Replication ==== | ||
Replication proceeds via θ (theta) replication after host gyrase supercoils the λ DNA. <ref name="Basic Virology"/> | |||
==== Late Gene Expression ==== | ==== Late Gene Expression ==== | ||
Revision as of 20:45, 3 August 2011
Bacteriophage λ is the archetype of the lambdoid, or lambda-like phage, a subclass of the siphoviridae. λ is a temperate phage. The λ strain used most often in labs, although called wt, is λPaPa, named after the parental strains from Pasedena California and the Institut Pasteur in Paris. [1]
Morphology
The λ phage has an icosahedral head about 50 nm in diameter, and a flexible, noncontractile tail about 150nm long.[2][1] The head is formed from the proteins E, D, B, W, FII, B*, X1, and X2. [3] The head is the capsid, and 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.[2] The DNA is linear when packaged, and recircularizes using host ligase at the cos (cohesive end site) once injected into the host.[2] [3] The wt λ does not have tail fibers, although these may be present on certain strains.[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.[2] 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. [2]
Early Gene Expression
The cro gene produces an immediate-early gene product.[4] CII and CIII are delayed-early gene products. [4]
Middle Gene Expression
DNA Replication
Replication proceeds via θ (theta) replication after host gyrase supercoils the λ DNA. [3]
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, and decendants of the prophage are capable of producing phage when the λ DNA excises from the host DNA. [5] The λ DNA is integrated at the attP (for attachment phage) and the attB (for attachment bacteria) loci.[4]
Lysis-Lysogeny Switch
Prophage Induction
See also
- Lambda Gene List
- Enterobacteriophage lambda at the NCBI taxonomy browser
- wikipedia: Lambda_phage
- ICTVdb entry
- Siphoviridae at MicrobeWiki
- Phage lambda on UniProt
References
See Help:References for how to manage references in EcoliWiki.
- ↑ 1.0 1.1 1.2 Hendrix, RW & Duda, RL (1992) Bacteriophage lambda PaPa: not the mother of all lambda phages. Science 258 1145-8 PubMed
- ↑ 2.0 2.1 2.2 2.3 2.4 Edited by Roger W. Hendrix, Jeffrey W. Roberts, Franklin W. Stahl and Robert A. Weisberg (1983) Lambda II (Cold Spring Harbor Laboratory, Cold Spring Harbor, NY)
- ↑ 3.0 3.1 3.2 Edward K. Wagner et al (2007) Basic Virology (Wiley-Blackwell) ISBN 978-1-4051-4715-6
- ↑ 4.0 4.1 4.2 Bruce A. Voles (2002) The Biology of Viruses (McGraw-Hill, Boston) ISBN 0-07-237031-9
- ↑ Appleyard, RK (1954) Segregation of Lambda Lysogenicity during Bacterial Recombination in Escherichia Coli K12. Genetics 39 429-39 PubMed