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In a series of seminal papers summarized in Annual Review in Genetics (2007) 41 1–11, Allan Campbell proposed a model that assumed phage lambda integration in its host (E. coli) genome. This is in contrast to plasmids and (as was shown much later) eukaryotic viruses such as, Herpesviruses, which are in synaptic association with their hosts' genomes but not physically integrated.

What experinets actually demonstrated that lambda genomes are integrated into E. coli DNA, rather than associated with the nucleoid?

Was the confirmation made using blotting techniques or more advanced methods?

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  • $\begingroup$ This might work here, but if not, then our History of Science and Mathematics site might be worth looking at as an alternative. $\endgroup$ Commented Jun 8 at 7:21
  • $\begingroup$ Sorry for the confusion. That is why I am looking for the papers that physically demonstrated lambda integration. Thanks $\endgroup$
    – Gigiux
    Commented Jun 9 at 6:26
  • $\begingroup$ OK. But the reference to herepesviruses (specifically EBV) is misleading, because this only became known much later. A more pertinent comparison would be with plasmids (discovered in the late 50s) as extrachromosomal genetic elements in bacteria. I will answer later unless someone else saves me the trouble. $\endgroup$
    – David
    Commented Jun 9 at 9:08
  • $\begingroup$ I remember reading the passage on herpes (and papilloma) in one of Campbell's articles but I can't find it back. I agree on moving the question on History of Science. Thanks $\endgroup$
    – Gigiux
    Commented Jun 9 at 13:50
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    $\begingroup$ I wouldn't move the question to History of Mathematics & Science. I have posted two useful question/answers there recently and the second got no response at all. If you look at the questions they are all Maths. I am going to start a couple of conversations on Meta to the effect that HMS drop the S and that we have an agreed policy to accept History of Biology questions. In my answer (to come) I will discuss the how (the who is uninteresting), which I think is relevant to this list. But a good answer requires time. $\endgroup$
    – David
    Commented Jun 9 at 16:02

1 Answer 1

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The Landy and Ross (reference 15)1 article in the review leads is an article freely available on PubMed Central.

Within in this review, there are further references, including a further review by Gingery and Echols (1967)2, which suggests that references 2-5 are related to this topic. Reference 2 is Campbell's theoretical paper suggesting the framework of insertion, and references 3 and 4 are both from 1965.

Reference 3 in the paper (and here too) is Franklin et al., The linear insertion of a prophage into the chromosome of E. Coli shown by deletion mapping, Biochemical and Biophysical Research Communications, Volume 18, Issues 5–6, 1965,3

Abstract:

Evidence bearing on the relationship of a prophage to the chromo- some of its host bacterium has been lucidly reviewed by Hayes (1964), who considered that a clear decision between attachment and insertion of prophage could not then be made. Just prior to Hayes' suammation, Campbell (1962) had formulated a largely theoretical model which would allow for the linear insertion of phage genetic material into a bacterial chromosome, and would account for the permuted gene sequence of the prophage as compared to vegetative phage. The permuted gene sequence had been indicated by comparisons of the gene order in phage recombination experiments and in crosses between bacteria lysogenic for genetically marked h prophages.(Calef and Licciardello, 1960). Evidence in support of the model was subsequently supplied by Campbell (1963) in studies of the segregation patterns of lysogenic heterogenotes, and by Rothman (1965) in studies of Pi cotransduction of galactose and 1 markers.

We describe in this paper observations which substantiate Campbell's model by showing that deletions in particular lysogenic bacteria simultaneously eliminate bacterial genes and segments of a prophage genome. The missing phage segments are overlapping, allowing sequencing of the prophage genes

Reference 4 is Rothman, Transduction studies on the relation between prophage and host chromosome, Journal of Molecular Biology, Volume 12, Issue 3, 1965.4

Abstract:

Cotransduction analysis by means of bacteriophage P1 has been used to study the relation between the bacterial genetic markers gal and bio and the prophage λ. The order of a series of markers of the λ prophage with respect to the bacterial gal locus has now been found. This marker order is a circular permutation of the order present in vegetative phage λ, in agreement with Campbell's hypothesis (1962). The frequency of cotransduction of gal and bio is drastically reduced when both donor and recipient strains are lysogenic either for prophage λ or prophage 82, an indication that both λ and 82 are located between the gal and bio markers. Additional evidence is presented suggesting that prophage 434 and the λ-434 hybrid may also be located between gal and bio.

It was not possible to find the order of the λ prophage markers with respect to the bio marker; hence, conclusive evidence for a linear insertion of the prophage into the bacterial chromosome could not be obtained.

The presence of a lambdoid prophage appears to affect the early steps of transduction by phage P1. The possible nature of this effect is discussed.

Thus, Franklin et al, provided the first evidence of the insertion of phage into bacterial genomes. Their work was largely performed by crossing of various mutants with non-replicative deletions on various permissive bacterial backgrounds, which led to the recognition that escape mutants, capable of replication had a homology in sequence between sites, which allowed recombinant excision out of the bacterial genome.

References:

  1. Landy A, Ross W. Viral integration and excision: structure of the lambda att sites. Science. 1977 Sep 16;197(4309):1147-60. doi: 10.1126/science.331474. PMID: 331474; PMCID: PMC1994661.

  2. Gingery R, Echols H. Mutants of bacteriophage lambda unable to integrate into the host chromosome. Proc Natl Acad Sci U S A. 1967 Oct;58(4):1507-14. doi: 10.1073/pnas.58.4.1507. PMID: 4867663; PMCID: PMC223953.

  3. Naomi C. Franklin, William F. Dove, Charles Yanofsky, The linear insertion of a prophage into the chromosome of E. Coli shown by deletion mapping, Biochemical and Biophysical Research Communications, Volume 18, Issues 5–6, 1965, Pages 910-923, ISSN 0006-291X, https://doi.org/10.1016/0006-291X(65)90868-5. (https://www.sciencedirect.com/science/article/pii/0006291X65908685)

  4. June L. Rothman, Transduction studies on the relation between prophage and host chromosome, Journal of Molecular Biology, Volume 12, Issue 3, 1965, Pages 892-912, ISSN 0022-2836, https://doi.org/10.1016/S0022-2836(65)80336-9. (https://www.sciencedirect.com/science/article/pii/S0022283665803369)

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  • $\begingroup$ Yes, but your answer would be more informative if you started with a one-sentence summary: "The final physical proof was the DNA sequencing of portions of the E.coli genome containing the junctions between the bacterial and integrated phage DNA (Landry and Ross, 1977)". $\endgroup$
    – David
    Commented Jun 10 at 9:16

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