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Enterobacteria phage λ (lambda phage, coliphage λ, officially Escherichia virus Lambda) is a bacterial virus, or bacteriophage, that infects the bacterial species Escherichia coli (E. coli). It was discovered by Esther Lederberg in 1950. [ 2 ]
Shiga toxins are a family of related toxins with two major groups, Stx1 and Stx2, expressed by genes considered to be part of the genome of lambdoid prophages. [1] The toxins are named after Kiyoshi Shiga, who first described the bacterial origin of dysentery caused by Shigella dysenteriae. [2]
A bacteriophage (/ b æ k ˈ t ɪər i oʊ f eɪ dʒ /), also known informally as a phage (/ ˈ f eɪ dʒ /), is a virus that infects and replicates within bacteria and archaea. The term is derived from Ancient Greek φαγεῖν (phagein) 'to devour' and bacteria .
Bacteriophage lambda encodes two repressors: the Cro repressor that acts to turn off early gene transcription during the lytic cycle, and the lambda or cI repressor required to maintain lysogenic growth. Together the Cro and cI repressors form a helix-turn-helix (HTH) superfamily. The lambda Cro repressor binds to DNA as a highly flexible dimer.
Lambdavirus (synonyms Lambda-like viruses, Lambda-like phages, Lambda phage group, Lambda phage) is a genus of viruses in the order Caudovirales, in the family Siphoviridae. Bacteria serve as natural hosts, with transmission achieved through passive diffusion. There are five species in this genus.
The discovery of the helix-turn-helix motif was based on similarities between several genes encoding transcription regulatory proteins from bacteriophage lambda and Escherichia coli: Cro, CAP, and λ repressor, which were found to share a common 20–25 amino acid sequence that facilitates DNA recognition. [2] [3] [4] [5]
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After Benzer demonstrated the power of the T4 rII system for exploring the fine structure of the gene, others adapted the system to explore related problems.For example, Francis Crick and others used one of the peculiar r mutants Benzer had found (a deletion that fused the A and B cistrons of rII) to demonstrate the triplet nature of the genetic code.