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At least 973 records · Page 54Linked to original sources
PubMed1988

Molecular Cloning and Expression of Cellulase Genes from Ruminococcus albus 8 in Escherichia coli Bacteriophage lambda.

A genomic library of Ruminococcus albus 8 DNA was constructed by using the Escherichia coli bacteriophage lambdaDASH. Recombinants were screened for cellulolytic activity by plating in soft agar (0.7%) overlays containing either 1% (wt/vol) carboxymethyl cellulose (CMC), 4-methylumbelliferyl-beta-d-cellobioside (MUC, 1 mg/ml), or 1% (wt/vol) Ostazin brilliant red-hydroxyethyl cellulose (OBR-HEC). One hundred and three recombinant phage exhibiting activity against OBR-HEC were found, and these fell into different classes based on the size of the zone of hydrolysis. Twenty-one recombinant phage exhibiting activity against CMC and 19 recombinant phage exhibiting activity against MUC were isolated. Four OBR-HEC, five CMC, and seven MUC clones were further analyzed by restriction endonuclease mapping and cellulase substrate specificity to identify unique clones and to determine their cellulase type. Three different clone types representing endoglucanase activity were identified. Three clones that appeared to encode exoglucanase type activity and four clones that had a mixed specificity, including beta-glucosidase activity, were also identified.

Journal Article↗
PubMed1972

Regulation of lambda rex expression after infection of Escherichia coli K by lambda bacteriophage.

The ability of Escherichia coli K to support bacteriophage T4rII replication starts to decline at 3 to 6 min after infection by lambda. This inhibition appears to depend on expression of the lambdarex(+) gene, since little inhibition was observed following infection by a lambdarex mutant or by a hybrid bacteriophage lambdai(434) which lacks a functional rex gene. For promotion of the synthesis of rex product, cII(+) and N(+) genes are required and can act trans, whereas cY(+), also required, must be cis to a rex(+) gene. These genes presumably play a role in the transcription of the cI-rex operon because they are also known to be required for repressor (cI product) synthesis. Functional cIII, O, P genes are not necessary for ample rex product synthesis. We also observed full rex expression after infection by lambdasuscI mutants, suggesting that rex and repressor are separate gene products and that repressor is not required for inhibition of T4rII replication. We also report experiments with a rex mutant that is not leaky when in a lysogen but is sufficiently leaky shortly after infection to cause inhibition of T4rII replication.

Chromosome Mapping↗
PubMed1971

Polar mutations in the left arm of bacteriophage lambda i434.

By studying complementation between frameshift and nonsense mutants located in the structural genes for the head of bacteriophage lambdai434, we found mutations in gene B which are polar on genes C and D and one mutation in gene E which is polar on gene F.

Acridines↗
PubMed1978

178-Nucleotide sequence surrounding the cos site of bacteriophage lambda DNA.

A nucleotide sequence of 61 nucleotides at the left end and 117 nucleotides at the right end of DNA from bacteriophage lambdacI857Sam7 was determined by the Maxam and Gilbert method. A perfect inverted repeat sequence of 10 nucleotides is near the left end, and one of 15 nucleotides is near the right end. DNA from another closely related lambda strain, lambdacI857prm116Sam7, has about 10% divergence in the sequence of the first 110 nucleotides at the right end and has a 17-member perfect inverted repeat sequence.

Base Sequence↗
PubMed1975

In vitro construction of bacteriophage lambda carrying segments of the Escherichia coli chromosome: selection of hybrids containing the gene for DNA ligase.

DNA from lambdagt-lambdaB bacteriophage was cleaved with EcoRI endonuclease and fragments from EcoRI-digested E. coli DNA were inserted. This DNA was used to infect E. coli, and phages containing the gene for DNA ligase were isolated by genetic selection. Two different hybrids were found with the same E. coli segment inserted in opposite orientations. Both hybrids produced similar levels of ligase as measured in crude extracts of infected cells.

Chromosome Mapping↗
PubMed1987

Synthesis of a trans-acting inhibitor of DNA maturation by prohead mutants of phage lambda.

Bacteriophage lambda with mutations in genes that control prohead assembly and other head precursors cannot mature their DNA. In this paper we present evidence that the failure of these phage mutants to mature DNA is a reflection of a mechanism that modulates terminase nicking activity during normal phage development. We have constructed plasmids that contain the lambda-cohesive end site (cos) and the genes that code for DNA terminase, the enzyme that matures DNA by cutting at cos. The DNA terminase genes are under control of a thermosensitive cI repressor. These plasmids lack most of the genes involved in prohead morphogenesis and other head precursors. However, when repression is lifted by destruction of the thermosensitive repressor, the terminase synthesized is able to cut almost 100% of the plasmids. Therefore, these plasmids can mature in the absence of proheads and other head gene products. The plasmids are also able to complement mutants of lambda deficient in terminase and DNA maturation. However, in these complementation experiments, if the phage carry mutations in prohead genes E or B, not only is phage DNA maturation blocked, but the plasmid also fails to mature. These experiments show that, in the absence of proheads, phage lambda produces a trans-acting inhibitor of maturation. The genetic determinant of this inhibitor maps in a region extending from the middle of gene B to the end of gene C. A model is proposed in which the nicking activity of DNA-bound terminase is inhibited by the trans-acting inhibitor. Prohead (and other factors) binding to this complex would release the block to allow DNA cleavage and packaging.

Bacteriophage lambda↗
PubMed1976

Attempts to purify a membrane attached chromoid of bacteriophage lambda.

Using methods which proved successful for the isolation of E. coli chromosome in a folded form (the E. coli chromoid), we have attempted to purity the "native" form of bacteriophage gamma chromosome from gamma infected cells. Upon sedimentation of lysates we find that phage DNA separates into two fractions, one of which cosediments with the bacterial chromoid ; the other sediments nearer to the top of gradient. Both fractions probably contain membrane-bound phage DNA, and both support the in vivo synthesis of phage DNA. The heavier fraction contains more closed circular parental DNA molecules than the lighter fraction. Formation of the latter is blocked by certain phage mutations. Being relatively free of bacterial DNA, the lighter fraction is suitable for further analysis.

Cell Membrane↗
PubMedDate not supplied

[Infectivity of different forms of lambda bacteriophage DNA in transfection of calcinated Escherichia coli].

Infectivity of linear lambdaDNA molecules is proved to be about a hundred times higher in calcinated E. coli K12 (lambai434) than in E. coli K12(lambda-): the levels of transfection were 1-3-10(7) and 1-2-10(5) infective centers per 1 mug DNA, respectively. In E. coli JC 5743 rec B21 defective for exonucleases I and V the level of transfection was 1-3-10(6). High infectivity of linear lambdaDNA in lysogenic cells cannot be explained by a helping effect of phage particles spontaneously liberated by these cells. It can be caused by recombinations of inserted lambdaDNA molecules with prophage or by the low activity of some nucleases in the lysogenic cells. Covalently closed and "Hershey" ring forms of lambdaDNA penetrate the calcinated cells as readily as linear molecules do but the infectivity of the former ones is proved to be very low.

Coliphages↗
PubMed2003

Interplay between DnaA and SeqA proteins during regulation of bacteriophage lambda pR promoter activity.

DnaA and SeqA proteins are main regulators (positive and negative, respectively) of the chromosome replication in Escherichia coli. Nevertheless, both these replication regulators were found recently to be also transcription factors. Interestingly, both DnaA and SeqA control activity of the bacteriophage lambdap(R) promoter by binding downstream of the transcription start site, which is unusual among prokaryotic systems. Here we asked what are functional relationships between these two transcription regulators at one promoter region. Both in vivo and in vitro studies revealed that DnaA and SeqA can activate the p(R) promoter independently and separately rather than in co-operation, however, increased concentrations of one of these proteins negatively influenced the transcription stimulation mediated by the second regulator. This may suggest a competition between DnaA and SeqA for binding to the p(R) regulatory region. The physiological significance of this DnaA and SeqA-mediated regulation of p(R) is demonstrated by studies on lambda plasmid DNA replication in vivo.

Bacterial Outer Membrane Proteins↗
PubMedDate not supplied

[Identification of partial hydrolysis products of lambda bacteriophage DNA by restriction endonuclease EcoRI].

The relationship between the electrophoretic mobility of double stranded DNA fragments electrophoresed in agarose gel and their molecular weights within the range from 1.10(6) to 8.10(7) daltons and agarose concentration 0.3--2.0% has been studied. Partial hydrolysis products of lambda phage DNA obtained by restriction endonuclease EcoRI have been separated. Partial hydrolysis products have been identified by determining the fragments of full cleavage as well as by genetic methods using a system of transformation of E. coli cells treated with CaCl2, which have been infected with different helper-phages containing definite gene mutations.

Coliphages↗
PubMed1978

Isolation and characterization of a plaque-forming lambda bacteriophage carrying a ColE1 plasmid.

A plaque-forming lambdaimm434 bacteriophage carrying the entire genome of colicinogenic factor E1 has been isolated and characterized. This phage, lambdaimm434ColE1, can lysogenize as a stable plasmid within a recombination-deficient Escherichia coli cell that lacks the normal attachment site for lambda phage. Furthermore, it has been found that lambdaimm434ColE1 phage carrying amber mutations in the O and P genes of the lambda genome, i.e., lambdaimm434OamPamColE1, behaves as a plaque-forming phage, and this finding suggests that the ColE1 factor DNA permits replication of the DNA of the plaque-forming phage.

Bacteriocin Plasmids↗
PubMed1977

Threonyl-transfer ribonucleic acid synthetase from Escherichia coli: subunit structure and genetic analysis of the structural gene by means of a mutated enzyme and of a specialized transducing lambda bacteriophage.

Threonyl-transfer ribonucleic acid synthetase (ThrRS) has been purified from a strain of Escherichia coli that shows a ninefold overproduction of this enzyme. Determination of the molecular weight of the purified, native enzyme by gel chromatography and by polyacrylamide gel electrophoresis at different gel concentrations yielded apparent molecular weight values of 150,000 and 161,000, respectively. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate yields a single protein band of 76,000-dalton size. From these results an alpha(2) subunit structure can be inferred. A mutant with a structurally altered ThrRS, which had been obtained by selection for resistance against the antibiotic borrelidin, was used to map the position of the ThrRS structural gene (thrS) by P1 transductions. It was found that thrS is located in the immediate neighborhood of pheS and pheT, which are the structural genes for the alpha and beta subunits of phenylalanyl-transfer ribonucleic acid (tRNA) synthetase, the gene order being aroD-pheT-pheS-thrS. A lambda phage that was previously shown to specifically transduce pheS, pheT, and also the structural gene for the translation initiation factor IF3 can complement the defect of the altered ThrRS of the borrelidin-resistant strain. This phage also stimulates the synthesis of the 76,000, molecular-weight polypeptide of ThrRS in ultraviolet light-irradiated. E. coli cells. These results indicate that the genes for ThrRS, alpha and beta subunits of phenylalanyl-tRNA synthetase, and initiation factor IF3 are immediately adjacent on the E. coli chromosome.

Amino Acyl-tRNA Synthetases↗
PubMed1969

Inactivation of bacteriophage lambda containing semiconserved alkylated deoxyribonucleic acid.

Immediate and delayed inactivation of ethylmethane sulfonate (EMS)-treated lambda phage were studied. Phage particles with one alkylated and one intact deoxyribonucleic acid (DNA) strand were obtained by allowing host-modified, EMS-treated phage to undergo one growth cycle in a nonmodifying host and selecting the progeny with semiconserved parental DNA on a restricting host. The results indicate that particles with one alkylated DNA strand are more sensitive to a second treatment with the alkylating agent. When incubated at 37 C, they are subject to inactivation at a rate which is smaller than that of phages containing two alkylated DNA strands. It appears that depurination events in one of the DNA strands of a phage particle are sufficient to cause death.

Alkylating Agents↗
PubMed1971

Bacterial mutants in which the gene N function of bacteriophage lambda is blocked have an altered RNA polymerase.

Bacterial mutants have been isolated, called groN, that block phage development by interference with the action of the product of the phage N gene. lambdatrp phages, which depend on the N product for the synthesis of tryptophan enzymes, do not make these enzymes in groN bacteria. Two type of phage mutants have been isolated that can overcome the groN block. One type makes an altered N product, the other contains an N-bypass mutation. The groN mutation is closely linked to the rifamycin-resistance locus in Escherichia coli. Purified RNA polymerase from the groN mutant is less activated by salt and more sensitive to rifamycin than is the polymerase from gro(+). This suggests that the groN mutation produces a structural change in the bacterial RNA polymerase such that it can no longer interact properly with the phage N product.

Bacterial Proteins↗