Differences in sensitivity of T3, T7, T4 and lambda phages to bleomycin and phleomycin]

In contrast to phage lambda the phages T3, T7 and T4 are not inhibited by as much as 150 microgram bleomycin/ml, while the chemically related antibiotic phleomycin increasingly inhibits the propagation of the phages in the order T4-T3-lambda. 20 microgram phleomycin/ml inhibit T3 by 95%. The resistance against bleomycin is surprising, because 10 microgram BM/ml block completely the colony-forming capacity of the host bacterium. The drug resistance of the phage growth correlates with the weak decrease of phage DNA synthesis, while the host cell DNA synthesis ceases rapidly. In accordance with these data is the in vivo inhibition of Escherichia coli cells and the in vitro degradation of their DNA. However, a contradiction exists between the in vivo resistance of T3 and T4 and the in vitro susceptibility of their DNA against nucleolytical fragmentation by bleomycin. The mechanism of the insensitivity of T3, T7 and T4 against bleomycin is unknown.     

Receptor-recognizing proteins of T-even type bacteriophages. The receptor-recognizing area of proteins 37 of phages T4 TuIa and TuIb

Escherichia coli phages of the T4 family (T4, TuIa, TuIb) recognize their cellular receptors by means of a C-terminal region of protein 37; a dimer of this polypeptide (1026 residues in T4) is located at the distal part of the long tail fibers. Virions of the T2 family use protein 38 (which is attached to the free end of protein 37) for this purpose. The corresponding areas of genes 37 belonging to TuIa and TuIb were cloned and sequenced. Comparison of the deduced protein primary structures, including those of T4 and lambda Stf (Stf most likely representing a subunit of the side tail fibers of phage lambda) showed that an area of 70 to 100 residues is characterized by very variable sequences, while the sequences of the adjacent 43 to 44 C-terminal residues as well as those upstream from the variable region are highly homologous. The variable regions are flanked and interrupted seven or eight times by the motif His-x-His-y, with x and y most often being Ser or Thr; furthermore, the locations of these repeated tetrapeptides are conserved. Using hybrid phages obtained by recombination of one phage with cloned fragments of gene 37 of another, it could be shown that the area of this gene encoding receptor specificity includes the variable area. The situation is analogous to the known receptor-recognizing region of proteins 38 belonging to the T2-type family, except that the repeating sequence is of a different nature. In T4, receptor specificity is coded for by 382 base-pairs of the 3'-end of the gene, starting exactly at the variable area. It was found that T4 can use the outer membrane protein OmpC or lipopolysaccharide as receptors with the same efficiency, and it is proposed that the 70 residues of the variable part of the protein serve to bind to both ligands.     

The use of bacteriophages of Bacteroides fragilis as indicators of the efficiency of virucidal products

The potential use of bacteriophage B40-8 of Bacteroides fragilis for the evaluation of the virucidal activity of antiseptics or disinfectants was investigated. The antiviral activity of two antiseptics and two disinfectants was evaluated according to a standard guideline. The effect of the virucidal agents was assessed on (i) viruses usually spread by direct contact with surfaces with contaminated secretions, i.e. herpes virus 1 and 2, and vaccinia virus, and (ii) viruses transmitted by the fecal-oral route, i.e. hepatitis A virus, poliovirus, adenovirus and rotavirus. The survival of B40-8 always equalled or exceeded that of the animal viruses tested. Our data suggest the use of bacteriophage B40-8 to complement the information furnished by some standardized methods in ascertaining the antiviral activity of virucidal preparations.     

Mutants of phage HK239 defective in excluding phages lambda T4rII, P1, and P2

Summary Escherichia coli cells lysogenic for temperate phage HK239 exclude phages , HK022, P1 vir, P2, and rII mutants of phage T4. After mutagenic treatment, four isolates were obtained for their inability to exclude T4rII. It is shown that this mutation, designated exc, is located in the prophage HK239, and that, it also abolishes the exclusion of phages , HK022, P1 vir, and P2.     

Formation of ion channels in the Escherichia coli cytoplasmic membrane after exposure to bacteriophages T4 and lambda

The effects of phage T4 and lambda on the ion permeability of the E. coli cytoplasmic membrane were studied. It was shown that the phage-induced depolarization of the membrane is coupled with a simultaneous increase in a transmembrane pH gradient. Hence, the total value of the proton-motive force remains unchanged at moderate multiplicity of infection. The rise in the pH gradient occurs due to an increase in the activity of the redox H+-pump of the E. coli membrane. Analysis of the temperature dependence showed that the stimulating effect of the phage is observed at 6-8 degrees C. Apart from the phages, gramicidin is also capable of stimulating the H+-pump under these conditions, while the stimulating effect of valinomycin is diminished. These data suggest that the ion-permeable channels are formed in the membrane during the interaction of E. coli cells with the phages. The experimental results demonstrate that the channels are permeable to ions of monovalent metals. The phage can also increase the permeability of cell membranes to protons; however, the permeability to monovalent ions is higher when these ions are in excess.     

Study of the transfer RNAs coded by T2, T4, and T6 bacteriophages.

T2, T4, and T6 bacteriophage tRNAs coding for arginine, leucine, proline, isoleucine, and glycine were isolated under conditions of short term and long term infection of Escherichia coli B cells. The corresponding phage tRNA species were examined for sequence homology by RNA-DNA hybridization analysis and by their relative behavior on reversed phase chromatography. The results indicate that all three T-even phages code for similar tRNA species; however, some tRNA species are homologous, others are not, and not all of the same tRNA species are coded by each bacteriophage. Reversed phase chromatography showed the presence of isoacceptor tRNAs for each phage aminoacyl-tRNA species. Pulse-chase experiments for [32P]tRNAGly suggest that the multiple isoacceptor species observed derive from the intracellular modification of a single tRNAGly gene product.     

The alpha-glucosyltransferases of bacteriophages T2, T4 and T6. A comparison of their primary structures

Summary With the aim of comparing the primary structures of gene products coded for by T-even bacteriophages we constructed clone libraries of the DNAs of bacteriophages T2 and T6. Using hybrid M13 phages carrying the gene for the T4-coded -glucosyl transferase (gt) we isolated corresponding T2 and T6 clones. The nucleotide sequences of the three gt genes and the amino acid sequences derived were compared. The differences between the genes and their products are discussed in terms of structure, function and evolutionary aspects.Abbreviations bp base pair - gt glucosyl transferase - HMC 5-hydroxymethyl cytosine - orf open reading frame - Xgal 5-bromo-4-chloro-3-indolyl--d-galactoside     

A study of triflupromazine in dominant-lethal, cytogenetic and host-mediated assays

The phenothiazine psychotherapeutant, triflupromazine (TFP), was studied for mutagenic potential in dominant-lethal, in vivo and in vitro cytogenetic and host-mediated assay procedures. No evidence of gross chromosomal aberrations or point mutations was detected in these assays even at dosage regimens which produced substantial lethality. The effect of the drug on body temperature was measured at the same doses used for mutagenicity testing. A marked and sustained temperature reduction occurs shortly after administration of as little as 10 mg/kg. Due to the pronounced physiological effects at these levels, the validity of mutagenicity studies conducted at the same levels may be seriously questioned.     

Effect of bacterial host repair systems on the viability of hydroxylamine and methyl methanesulfonate treated T4 and lambda bacteriophages

Summary Survival of HA or MMS-treated T4 and lambda phages was estimated in bacterial cells differing in their ability to repair DNA. It has been found that the mismatch repair system of the bacterial host, which involvesmutSmutRmutLuvrE anddam loci, does not excise, or does so to only a limited extent, the nonpaired bases from DNA of HA or MMS-treated phages. Mutation inpolA, both in the polymerase as well as in the 53 exonuclease activity, have a small effect on survival of HA-treated phages, whereas mutation in the polymerase activity has a pronounced effect on survival of MMS-treated phages. There was a difference in the effect of polA mutations on survival of MMS-treated T4 and lambda phages; the survival of the former was less affected than the latter. Induction of SOS response has no effect on repair of HA and MMS-treated phages. Pretreatment of bacterial host (including theada ^- mutant) with low doses of alkylating agents increases the survival of MMS (but not HA)-treated phages; pretreatment of bacteria with HA has no effect on survival of HA-treated phages. Three lines of evidence: the different inactivation rates of MMS-treated T4 and lambda phages, variation in the effect ofpolA mutations on survival of T4 and lambda phages, and a different level of adaptive response inada ^- cells towards of MMS-treated T4 and lambda phages, suggest that the patterns of DNA methylation in T4 and lambda phages are different.     

Transient electric birefringence of T-even bacteriophages. II. T4B in the presence of tryptophan and T4D.

Measurements of electric birefringence, sedimentation velocity, and biological adsorption rate are used to study the properties of bacteriophage T4B in the presence of excess tryptophan. The adsorption rate determined in borate buffer pH 9 (at 25°C) increases from 0.003 × 10^?8 ml min^?1 (0.025 M) to 0.130 × 10^?8 ml min^?1 (0.150 M). The Kerr coefficient, rotational diffusion coefficient, and the sedimentation coefficient of the phage are also dependent on buffer concentration and reach plateau values above 0.12 M given by K_sp = ?(275 ± 18) × 10^?9 OD^?1 cm² statvolt^?2, D_25,w = 133 ± 4 sec^?1, and s_20,w = 818 ± 11 S. From a comparison of electric birefringence measurements of T4B and T4D it is concluded that T4D and T4B (in the presence of excess tryptophan) exhibit a similar hydrodynamic behavior. The change in physical parameters is solely due to a shift in fiber configuration. At high buffer concentrations the fibers make an angle of approximately 3π/4 with the sheath and the permanent dipole moment is about 200,000 D. This dipole moment is roughly ten times as large as that of a phage particle with nonextended fibers. This difference may be due to a change in hydrodynamic center upon fiber extension or to the presence of positive charges on the fiber tips, or both. At intermediate buffer concentrations the phage population behaves as if it were monodisperse. Probably not all six fibers are extended under such conditions.