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PubMed1975

Isolation and properties of a conditionally lethal bacteriophage lambda mutated in the chi region.

A thermosensitive lambda phage mutant was isolated which can grow at high temperature only in the presence of the lambda chi gene product supplied in trans. This mutation tn was mapped within the chi region, and lambda tn phage expressed the pRoR-OP operon only poorly at high temperature. Effects of the tn mutation on expression of other operons were also examined and compared with those observed with cro27 or some tof mutations.

Chromosome Mapping↗
PubMed1977

Kinetics of induction of error-prone repair of bacteriophage lambda by temperature shift in an Escherichia coli dnaB mutant.

Preincubation at 42 degrees, before infection at permissive temperature by phage lambda, of an Escherichia coli dnaB mutant, provokes a significant increase in survival and mutagenesis of ultraviolet irradiated phage as well as mutagenesis of untreated phage. Similarly to UV irradiation and many chemical mutagens, the inhibition of DNA synthesis by temperature shift of this dnaB mutant induces SOS repair. This work shows that replication blockage in bacterial DNA is not only mutagenic for bacterial DNA itself (Witkin, 1975) but also for normally replicating lambda DNA, probably due to induction of diffusible products.

Coliphages↗
PubMed1977

Formation of recombinant DNA of bacteriophage lambda by recA function of Escherichia coli without duplication, transcription, translation, and maturation.

Genetic recombination of phage lambda DNA mediated by Rec function of Escherichia coli was studied in the absence of duplication, transcription, translation, and maturation. Cells were jointly infected with double amber mutants, lambda D-F-I and lambda S-R-, and incubated in the presence of chloramphenicol and rifampin. The am+ recombinant DNA molecules formed within the cell were detected by in vitro packaging as viable recombinant phages. This system was used to measure the recombination activity of rec- bacteria. In recA or recA recB bacteria, the number of recombinant DNA molecules was about 1% of the rec+ level. In contrast, almost normal numbers of recombinant DNA molecules were formed in recB or recC cells. Therefore, (1) the recombination mediated by recA function does not need de novo protein synthesis; all gene products required for the recombination are present in the cell. (2) It can occur without duplication, transcription, and maturation of recombining DNA molecules. (3) The ATP dependent DNase (exonuclease V) controlled by recB and recC genes is not required for formation of recombinant DNA molecules.

Adenosine Triphosphate↗
PubMed1979

A study of the organisation of the ribosomal ribonucleic acid gene cluster of Neurospora crassa by means of restriction endonuclease analysis and cloning in bacteriophage lambda.

1. Total Neurospora crassa DNA was restricted with endonucleases and fragments carrying rRNA coding sequences were identified by hybridization with Xenopus laevis ribosomal DNA probes. 2. The repeating unit of the rRNA gene cluster was found to be 8.6 kbp, arranged in a head-to-tail fashion. 3. Digestion with Hind III yielded fragments of 3.4 kbp and 5.2 kbp and both were cloned. 4. Digestion with Eco RI yielded fragments of 2.2 kbp, 3.0 kbp and 3.4 kbp; the 3.0 kbp fragment was cloned. 5. Sequences coding for RNA (S-rRNA)1 of the smaller subribosomal particle were found (at least 90%) in the 2.2 kbp EcoRI subfragment of the 5.2 kbp Hind III fragment. 6. The coding sequences for the major RNA species (L-rRNA) of the larger subribosomal particle were located mainly (at least 95%) in the 3.4 kbp Hind III fragment. 7. For comparison, a Hind III digest of total yeast DNA was cloned and recombinants containing a 6.4 kbp rDNA fragment were isolated.

Animals↗
PubMed1977

Mapping of restriction sites in the attachment site region of bacteriophage lambda.

A find structure map of the EcoRI fragment containing the lambda attachment-site region has been constructed. 38 different restriction endonucleases have been employed and 170 sites located in this fragment. In addition, sites in adjacent regions have been determined for several enzymes. Complete cleavage maps of the entire lambda genome have been obtained for endonucleases BglII, BluI, KpnI, SacI, SacII, SalI and XbaI. The strategy employed for mapping included comparison of deletion and substitution mutants, analysis of mixed digests, and detailed analysis of subfragments.

Chromosome Mapping↗
PubMed1976

Heat-sensitive DNA-binding activity of the cI product of bacteriophage lambda.

The binding of lambda gene cI product to lambda DNA was studied at temperatures from 0 degrees C to 46 degrees C. Binding activity of the products of cIts mutants was higher at 22 degrees C than at 0 degrees C, 26 degrees C or 30 degrees C. Both cI+ and cIts products lost DNA-binding activity at 46 degrees C, but after subsequent cooling to 22 degrees C, they regained 50-100% of their activity.

Cold Temperature↗