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PubMed1977

UV-induced alleviation of K-specific restriction of bacteriophage lambda.

A partial release of K-specific restriction of phage lambda grown in Escherichia coli C was observed when E. coli K strains AB1157 (having wild-type repair of UV-produced DNA damage) and AB1886 (uvrA) were irradiated with UV light before infection. The effect occurred in AB1886 at lower UV fluences than it did in AB1157. Little or no release of restriction was observed when AB2463 (recA) or AB2494 (lex-1) was used. Such release of restriction appears to be another of the UV-induced phenomena associated with "SOS" repair.

Coliphages↗
PubMed1977

Genetic and physiological control of host cell lysis by bacteriophage lambda.

The timing of host cell lysis at the end of the lytic cycle of phage lambda is under complex control. The lambda S protein stimulates lysis. Another physiological system, the lysis regulator, inhibitis lysis from occurring prematurely. The effects of a series of phage and bacterial mutations on these controls are described. They show that the lambda rex gene plays a role in regulating lysis under suboptimal growth conditions. In certain mutant cells, and especially under anaerobic culture conditions, the rex gene aids in the scheduling of host cell lysis. The data also suggest that the lysis regulator may control the transition of the lambda S protein from an inactive to an active state.

Anaerobiosis↗
PubMed1978

Exclusion of bacteriophage T1 by bacteriophage lambda. I. Early exclusion requires lambda N gene product and host factors involved in N gene expression.

Two modes of exclusion of T1 by lambda are distinguished. "Early" exclusion depends on gene N, but not on gene Q. It is at least partially ineffective against T1am23. "Late" exclusion depends on gene Q and effects T1am23 as well as T1+. Early exclusion is a direct effect of N gene product, rather than N gene being required for the expression of some other lambda gene. Three host mutations, groN, nusA, and nusB, known to interfere with lambda replication by affecting N gene expression, also interfere with the ability of lambda to exclude T1.

Coliphages↗
PubMed1978

Anomalous behavior of bacteriophage lambda polypeptides in polyacrylamide gels: resolution, identification, and control of the lambda rex gene product.

The resolution of lambia proteins was compared on the two types of sodium dodecyl sulfate-polyacrylamide gels commonly in use. The two kinds of gel differ essentially in the ratio of the cross-linker, N'-N-bismethylene-acrylamide (bisacrylamide), to acrylamide monomer. Several lambda proteins migrate relatively more slowly in gels with high bisacrylamide/acrylamide ratios (HB gels) than in gels with low ratios, although the two types of gel are of roughly equivalent porosity. This effect is illustrated by a change in relative position of both the Rex and Int proteins, with apparent increases in molecular weight of about 8 and 15%, respectively, in the HB gels. This work confirms that like repressor and Int, the 28.5-kilodalton protein, identified as Rex on HB gels, is postively regulated by the lambdacII and cIII products and negatively controlled Cro. An intact y site is required for Rex and repressor expression after infection, whereas their synthesis in a lysogen is dependent upon a functional maintenance promoter, Prm.

Coliphages↗
PubMed1978

Bacteriophage lambda mutants (lambdatp) that overproduce repressor.

Lambda tp mutants, selected for their ability to form turbid plaques on lon hosts, overproduce repressor. The tp1 and tp2 mutations have been located within (or adjacent to) the cIII gene. The tp1 mutation reduced late gene expression, as measured by endolysin synthesis (in the absence of functional cI repressor) and progeny phage yield. The tp4 mutation was mapped in the cY-cII region, and complementation tests indicated that tp4 affects the diffusible product of the cII gene. The tp4 mutation also reduced progeny production, but did not markedly affect endolysin synthesis.

Coliphages↗
PubMed1979

Construction and characterization of the hybrid bacteriophage lambda Charon vectors for DNA cloning.

Twenty hybrid lambda phages especially designed for molecular cloning have been constructed and named Charon phages. These phages differ in the ranges of sizes of DNA fragments that may be inserted, by the selections and screens which may be used to isolate and detect the incorporation of cloned fragments, by the way transcription of the cloned fragment may be controlled, by the different restriction enzymes that can be used for cloning, by the phage immunities that may be employed for controlling replication and transcription, and by the biological safety features that they contain. The crosses used to produce the vectors are described, and their genealogy is discussed. The structure of each vector has been verified by genetic tests, by DNA length determinations, by electron micrographic analysis of DNA heteroduplexes, and by gel electrophoresis of restriction enzyme digests. In the course of these constructions, a new EcoRI site was found in a derivative of lambda Aam32Bam1 which maps very near the left cohesive end of lambda.

Coliphages↗
PubMed1979

Novel bacteriophage lambda mutation affecting lambda head assembly.

A novel phage lambda mutation, called dc10, which interferes with proper lambda head assembly has been isolated and characterized. Phage lambda carrying this mutation is (i) unable to form plaques at 30 or 37 degrees C but does so at 42 degrees C and (ii) unable to form plaques at 42 degrees C on pN-constitutive hosts. Both properties are due to dc10 since all phage revertants for one phenotype simultaneously lose the other phenotype and vice versa. The dc10 mutation has been mapped in the B gene and has been shown to be dominant over the corresponding wild-type product. At 30 degrees C the dc10 mutation results in the formation of abnormal petit lambda heads made up of pE, pB, pC, and pNu3. Under pN-constitutive conditions, the dc10 mutation results in the formation of abnormal petit lambda heads made of pE, X1, and X2 only. A model to explain the data is presented.

Coliphages↗
PubMed1971

Sensitivity of intracellular bacteriophage lambda to colicin CA42-E2.

Treatment of Escherichia coli K-12 infected by lambda CIts857 with colicin CA42-E2 resulted in partial inhibition of the infectious process. Uninfected bacteria were killed by colicin with a probability of about five times that with which similarly treated lambda-infected bacteria lose plaque-forming ability. The lambda deoxyribonucleic acid (DNA), when present in a bacterial cell either as the replicating DNA of infectious phage or as the nonreplicating DNA of superinfecting phage, was degraded to acid-soluble material after colicin treatment. Analysis of the intermediates of DNA breakdown has revealed that degradation of the DNA to acid-soluble material is preceded by endonucleolytic fragmentation of the chromosome at a limited number of sites. This is the same mechanism of degradation previously observed for E. coli DNA after colicin treatment.

Carbon Isotopes↗
PubMed1975

Termination of transcription in bacteriophage lambda. Heterogeneous, 3'-terminal oligo-adenylate additions and the effects of rho factor.

RNA transcripts were synthesized in vitro from a lambda DNA template with purified Escherichia coli RNA polymerase either in the presence or absence of the protein termination factor, rho. The products were initially characterized by electrophoresis on polyacrylamide slab gels, and two of the lower molecular weight discrete species (6 S and 4 S RNA) were further characterized by standard two-dimensional "fingerprint" analysis. Production of the 4 S RNA was strongly affected by the presence of rho, whereas production of the 6 S RNA species was relatively unaffected by rho. 3'-Terminal oligonucleotide fragments were then selectively isolated on columns of dihydroxyboryl-substituted cellulose from these transcripts. Sequence analysis of these oligonucleotide products indicated: (a) that all of the transcripts examined possess similar degrees of 3'-terminal sequence heterogeneity which consisted predominantly of the addition of 1 to 5 adenylate residues to the 3'-terminus of the transcript; and (b) that rho factor-enhanced termination results in a definite structural change in the nucleotide sequence with which an RNA molecule can terminate.

Adenine Nucleotides↗
PubMedDate not supplied

[Selection and some properties of recombinant clones of lambda bacteriophage containing structural genes of Drosophila melanogaster].

The lambdagt clones containing fragments of D. melanogaster genome were prepared and characterized by hybridization of their DNA with complementary RNA synthesized on the lambdagt DNA, C fragment of lambdagt DNA and total D. melanogaster DNA, and also with mRNA and a stable cytoplasmic poly(A)-RNA both isolated from D. melanogaster cells grown in culture. The technique for a simple selection of hybrid clones is described. The hybridization with mRNA allows one to select the clones containing structural genes of D. melanogaster. It was found that in all cases when the clone contains the structural gene it also contains the reiterated base sequences of the D. melanogaster genome. Several clones containing D. melanogaster DNA fragments with a size of (2--4) X 10(6) daltons which hybridized with a relatively large portion of mRNA were selcted for further analysis.

Animals↗