The role of the lysines in the alkaline heme-linked ionization of ferric cytochrome c.

Phage ?¹⁵ adsorbed at a low temperature (or by short-time incubation) to the outer surface of $\text{Salmonella}\text{anatum}$ gathers on further incubation at a high temperature to a certain region where the inner and outer membranes may join. This was demonstrated by separating the inner and outer membranes of the cells in sucrose gradient after addition of ³⁵S-labeled ?¹⁵ to the cells. Radioactivity adsorbed at 4° was first recovered mainly with the dense outer membrane but disappeared by further incubation at 35° within 5 min. Instead, the radioactivity was recovered with the membrane fraction which had intermediate density. Such phage translocation was not observed when phage ?¹⁵ was added to a $\text{pep}\text{mutant of}\text{S.}\text{anatum}$ to which the phage can adsorb but fail to infect. A host range mutant phage which can infect the $\text{pep}$ mutant migrated to the intermediate dense region.     

Prophage P2 does not kill recB bacteria.

$\text{Escherichia}\text{coli}$ carrying a temperature-sensitive $\text{recB}$ mutation and lysogenic for phage P2 was able to grow normally even at 42°C, at which temperature the bacteria are phenotypically $\text{recB}{}^{\mathrm{?}}$. At this temperature, the bacteria were, however, unable to support the growth of λspi^? phages.     

Identification of an Escherichia coli inner membrane polypeptide specified by a lambda-tonB transducing.

Analysis by polyacrylamide gel electrophoresis of the proteins coded by a λ$\text{ton}$B transducing phage, after infection of UV-irradiated bacteria, revealed the presence of at least 7 new polypeptides. Three of these were identified as proteins of the $\text{trp}$ operon whilst three others were deleted by a spontaneous mutation in the $\text{ton}$B region carried by the phage. A single polypeptide, molecular weight 40,000 was absent from a phage carrying a proflavine induced mutation in $\text{ton}$B. We conclude that this protein, which was localised in the inner membrane by sarkosyl fractionation of the envelope, is the $\text{tonB}$ product.     

On the defect of a dCMP hydroxymethylase mutant of bacteriophage T4 showing enzyme activity in extracts

Infection by $\text{L}\text{13}$, a temperature-sensitive mutant of gene 42 of phage T4, the structural gene for dCMP hydroxymethylase, previously was shown not to form T4 DNA at nonpermissive temperatures. Yet the enzyme activity was found in extracts. Since inactivation of the enzyme was not reversible, we have examined acid-soluble extracts of cells infected at nonpermissive temperature by $\text{tsL}\text{13}$ for 5-hydroxymethyldCMP in order to determine whether the enzyme functioned $\text{in vivo}$. A double mutant of $\text{tsL13}$ and $\text{amB}\text{24}$ (5-hydroxymethyldCMP kinase) did not form the nucleotide at nonpermissive temperature, but the control, $\text{amB}\text{24}$, formed large quantities. From these results and previous temperature-shift studies it is suggested that the enzyme is normally activated to function $\text{in vivo}$ between 5 and 8 minutes after infection.     

Properties and structure of a gene 24-controlled T4 giant phage

Giant T4 bacteriophage were found by Doermann et al. (1973a) with point mutants in gene 23 and by Cummings et al. (1973) after l-canavanine induction followed by an arginine chase. We now find T4 giant phage with 14 out of 15 tested temperature-sensitive mutants in gene 24 grown at intermediate temperatures between 33 °C and 37 °C.For one of these mutants, T4,24(tsB86), we found that (a) the optimum temperature for giant phage production is 34.8 °C, (b) the head-length distribution peaks sharply between 10 and 12 normal T4 phage head lengths, (c) about 75% of our giant phage have two tails, (d) the buoyant density in CsCl is greater than that of normal phage, (e) they are infectious and show an increased u.v. resistance, (f) their sodium dodecyl sulphate gel electrophoresis pattern is qualitatively similar to that of normal T4 phage, although the relative intensities of some of the bands are different, showing for example, a decreased $\text{P24}{}^1\text{P23}{}^1$² ratio, (g) optical diffraction and filtering of the flattened cylindrical part of the giant heads show a p6 surface net with a lattice constant of approximately 130 Å, a unique $\text{u}\text{v}$ ratio of $\text{15}\text{5}$ and a capsomer morphology of the type 1 + 6 + 6.Mixed infections with T4 wild type and T4.24(amN65) also yield giant phage. These are produced in highest amounts with a multiplicity of infection ratio of 5:5; no giants are observed at ratios of 1:9 or 9:1, suggesting that their formation may be caused by a dosage effect of P24.     

Repair of deaminated cytosine residues of DNA: biological significance of the absence of uracil from DNA.

Uracil-DNA glycosylase of $\text{Bacillus}\text{subtilis}$ is involved in repair of deaminated cytosine residues of DNA. Survivals of SPO2 phage after treatment with bisulfite and weak alkali are considerably higher in wild type strains than in $\text{urg}$ mutants, which are deficient in the enzyme activity, whereas survivals of bisulfite/alkali-treated PBS1 phage in the two types of cells are essentially the same. The spontaneous mutation frequency of a $\text{urg}$ mutant is three fold higher than is that of a wild type strain.     

The separation of phage promoter from bacterial lac promoter for beta-galactosidase expression in transducing phage lambda plac5.

The replication defective transducing phage λp$\text{lac}\text{5}\text{O}\text{29}\text{P}$3 carries a portion of the $\text{E.}\text{coli}\text{lac}$ operon in the $\text{b}$2 region of the lambda phage. This $\text{lac}$ operon segment contains the $\text{lac}$ promoter, the $\text{lac}$ operator, and the β-galactosidase $\text{z}$ gene, but does not contain the $\text{lac}$ repressor $\text{i}$ gene. The $\text{z}$ gene can be expressed from both the inserted $\text{lac}$ promoter and the phage promoter. When $\text{E.}\text{coli}$ strain 594 ($\text{z}$^?, $\text{i}$⁺) or JC6256 (Δ$\text{lac}$) is infected by λp$\text{lac}\text{5}\text{O}\text{29}\text{P}$3 in the absence of additional cyclic AMP, β-galactosidase synthesis is shown to be expressed from the phage promoter. When 594 (λ⁺) or JC6256 (λ⁺) is infected by λp$\text{lac}\text{5}\text{O}\text{29}\text{P}$3 in the presence of additional cyclic AMP and IPTG, β-galactosidase synthesis is shown to be expressed from the inserted $\text{lac}$ promoter.The ability to separate the phage promoter from the inserted $\text{lac}$ promoter for β-galactosidase expression will simplify the interpretation whenever λp$\text{lac}$5 is used.     

Plasmid vectors for high-efficiency expression controlled by the PL promoter of coliphage lambda

A family of plasmid cloning vectors has been constructed that make use of the leftward promoter ($\text{P}{}_{\mathrm{<mtext>L</mtext>}}$) of phage λ to provide for efficient expression of cloned genes in Escherichia coli. The promoter activity of $\text{P}{}_{\mathrm{<mtext>L</mtext>}}$ is fully repressed at low temperature by a thermolabile repressor product of the $\text{λc}\text{I}\text{1857}$ gene, and can be activated by heat induction. Examples are given (β-lactamse, tryptophan synthetase A) where, under optimal conditions, between 30 and 40% of the total protein synthesis is directed by the cloned gene under $\text{P}{}_{\mathrm{<mtext>L</mtext>}}$ control.     

Carbon monoxide and hydroxymercuribenzoate sensitivity of a fatty acid (omega-2) hydroxylase from Bacillus megaterium.

DNA-free minicells of $\text{Escherichia coli}$ will not allow growth of phage T-7, nor is RNA synthesis stimulated by phage infection. Thus, these miniature cells seem not to contain $\text{in vivo}$ RNA polymerase activity. However, DNA-dependent RNA polymerase activity can be unmasked in extracts with poly(dA-T) and Mn²⁺. This activity may represent a cytoplasmic pool of inactive RNA polymerase in normal cells.     

A mutation affecting the valine sensitivity of the acetohydroxyacid synthase III isoenzyme in E. coli K-12

The $\text{ilv-751}$ mutation (obtained by $\text{mu}$ phage mediated mutagenesis) affects the sensitivity to valine inhibition of the acetohydroxy acid synthase III isoenzyme of $\text{E. coli}$ K-12, as shown by constructing multiple mutants containing the $\text{ilv-751}$ mutation and only one of the genes for the expression of the three acetohydroxy acid synthase isoenzymes, at once. The mutation is dominant. This suggests that the phenotype of $\text{ilv-751}$ mutation is not caused by inactivation of a gene concerned with the expression of the AHASIII enzyme, consequent to prophage insertion into that locus.     

Ultraviolet light-induced recombination

Stimulation of transduction in $\text{Escherichia coli}$ by ultraviolet irradiation of the transducing phage P1 requires the $\text{uvrA-uvrB}$ nuclease but not the $\text{uvrC}$ product or DNA polymerase I. It is hypothesized that the first step in “normal” recombination can be bypassed by any procedure generating single-stranded ends of DNA (as, for example, by $\text{uvra-uvrB}$ nuclease activity).     

Transduction in Bacillus megaterium.

A bacteriophage, MP13, isolated from the soil on $\text{B. megaterium}$ QM B1551 has been found to transduce several auxotrophic markers. Transduction required inactivation of the phage to approximately 0.01% survival with UV light and it was enhanced by the absence of salts that are probably necessary for phage readsorption.     

Growth of phages lambda, phiX174, and Ml3 requires the dnaZ (previously dnaH) gene product of Escherichia coli

A functional $\text{dnaZ}$ (previously designated $\text{dnaH}$) product, known to be involved in DNA polymerization, is required for phage λ, ØX174, and M13, but not T4 or T7, growth.     

Inhibition of exonuclease V after infection of E. coli by bacteriophage T7

Exonuclease V ($\text{recBC}$ DNase) is inactivated in $\text{E. coli}$ between 4 and 7 min after infection by T7. This process requires protein sythesis. The inactivation does not occur when T7 is deficient for its RNA polymerase and thus does not express the genes involved in DNA replication and phage maturation. Some implications of this new function of T7 are discussed with respect to the processes of infection and DNA replication.     

Gene m3 mediated efflux of intracellular leucine from bacteriophage P22 infected Salmonella typhimurium

Infection of $\text{Salmonella}\text{typhimurium}$ with the $\text{m}{}_3$ mutant of bacteriophage P22 leads to a rapid and severe efflux of intracellular leucine. The superinfection exclusion ($\text{sie}$) genes of P22 interfere with the function of $\text{m}{}_3$ gene, the product(s) of which is speculated to be an internal protein of phage P22.     

The mechanism of integration of phage Mu in the chromosome of Escherichia coli.

Cultures of synchronized $\text{E. coli}$ were infected with phage Mu at various stages of the division cycle. Phage integration at a given locus on the chromosome was measured by the lost of the corresponding gene function. For several loci, maximal integration occured at gene locus during replication of that locus.     

Regulation of the in vitro synthesis of the alpha-peptide of beta-galactosidase directed by a restriction fragment of the lactose operon.

The regulation of the $\text{in vitro}$ synthesis of the N-terminal portion of the β-galactosidase molecule (α-peptide) has been investigated using DNA fragments of the lactose operon as template. DNA fragments of about 789 base pairs were isolated after endonuclease (Hin II) digestion of either λplac5, λh80dlacp^s or λh80dlacUV5 phage DNA or DNA from the recombinant plasmid PMC3. The regulation of the expression of these fragments is similar to that observed for the synthesis of β-galactosidase using total phage or plasmid DNA as template, indicating that the regulatory regions on the fragments are intact and functional. Thus, the synthesis of the α-peptide required an inducer due to the presence of $\text{lac}$ repressor in the $\text{E. coli}$ S-30 extract used. In addition a dependency on adenosine 3′,5′-cyclic monophosphate (cAMP)¹ for α-peptide synthesis was obtained with the fragments isolated from λplac5 and λh80dlacp^s DNAs, whereas little effect of cAMP was seen with the fragment isolated from λh80dlacUV5 phage DNA or PMC3 plasmid DNA containing a UV5 promotor region. However, a significant difference in the effect of guanosine-3′-diphosphate-5′-diphosphate (ppGpp) was observed. With the total phage DNA as template, ppGpp resulted in a 2–4 fold stimulation whereas with the fragment, or PMC3 plasmid DNA, directed synthesis of the α-peptide no significant stimulation by ppGpp was seen.     

Uncoupling of mitochondrial oxidative phosphorylation by thallium.

The mechanism of integration of λ$\text{bio}$ll, which is deleted of all the known λ recombination genes, was studied using $\text{bio}$ deleted hosts as recipients. The presence of $\text{rec}$BC DNase and $\text{exo}$I in the recipient cells affected the fate of λ$\text{bio}$ll DNA. In nine of ten $\text{imm}\text{λ}{}^{\mathrm{+}}$ transductants, insertion of the λ$\text{bio}$ll genome took place somewhere between J and N and the remaining one had abnormally permuted prophage λ. In this lysogen (#42), the sequence of prophage genes was similar to that of vegetative phage λ. The properties of lysogen #42 were compared with those of other lysogens.