ISSN:
1617-4623
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary Lambda bacteriophage mutants, λsar, were isolated. These mutants can form plaques on a non lysogenic lawn and are unable to grow on nonimmune (imm −),cro constitutive hosts. Analysis of the restriction of λsar by a set of defective lysogens suggested that both thecro andcII gene products participate in the inhibition. Thesar mutations were mapped in theori region between the genescII andO. Complementation experiments showed that under the restrictive conditions λsar is defective in the expression of both theN and theO genes. Transcription analyses support these findings, as λsar is unable to serve as a template for transcription after infectingcro constitutive hosts. In addition λsar does not replicate under the restrictive conditions, although its DNA can bind to the host membrane to some extent. TheSar phenotype can be relieved by removing sites of action ofcro either by aV2 mutation or by substituting the λ immunity region byimm434 orimm21. Similarly introducing acy mutation, which interferes with the action of thecII gene product, also eliminates theSar effect. Thesar mutation can suppresscy mutations as manifested in plaque morphology, lysogenization frequency,cI repressor synthesis and the expression ofrex function. Suppression takes place only when thesar mutation is present incis tocy and it requires the action of thecII andcIII gene products. It is suggested that thesar mutation suppressescy by activating a new promoter for repressor synthesis,pro. The results also suggest that thecII andcIII gene products may act at a site other thany.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02428115
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