ISSN:
1617-4623
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary A selection technique, using the thermoinducible prophage λCI857Nsus7 Nsus53, has lead to the characterization of a new class of prophage mutations (called r), which prevent host killing upon thermal induction. N-defective r mutants efficiently complement λi434 or λO and P mutants, but not the corresponding mutants of λi21. Complementation data suggest that the λi21 hybrid fails to provide the positive regulatory mechanism dependent on the λN-gene product, since it cannot activate the Q gene of a λN-defective mutant. Thus, it seems possible that r mutants cannot express genes O and P unless the N-gene product is present in the cell. This interpretation is supported by the fact that r mutants are not defective and form plaques when their N-gene is functional. r mutation confer a clear phenotype, and map in the y-CII region. Results of a density gradient analysis suggest that they result from small insertions of DNA. Induced N-defective r prophages appear to be only poorly transcribed on strand H. Complementation tests performed in a strain lysogenic for λ indicate that the C17 mutation can suppress a r mutation in a cis position, even in the absence of the N-gene product. These results suggest that the expression of genes O and P, in addition to gene Q, is under the positive regulation of the N-gene product.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00283357
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