A comparison of Selas and membrane filters for the sterilization of bacteriophage preparations

Lysates of three different coliphage were sterilized by filtration through Selas, Millipore GVWP, and Millipore GS filters. Phage titers were comparable when either the Selas or Millipore GVWP (hydrophilic) filters were used; however, the GVWP filters were faster and could accommodate more lysate before the filters clogged. The Millipore GS (hydrophobic) filters were unsatisfactory.

Inhibition of bacterial segregation by early functions of phage mu and association of replication protein B with the inner cell membrane

Infection of Mu-sensitive bacteria with a recombinant lambda phage that carries the EcoRI.C fragment from the immunity end of wild type Mu DNA causes filamentous growth. Transmission electron microscopy revealed that the cell-division cycle was inhibited at, or prior to, the initiation of septation. The filamentation does not occur after infection of Mu-immune bacteria or after infection with a phage carrying the same EcoRI.C fragment, but with an IS1 insertion in gene B of Mu, showing that either gpB and/or some non-essential functions (e.g. kil) mapping downstream from the insertion are required for the inhibition of cell division. These data and previously published evidence suggest that in the "killing" of E. coli K12 by early Mu functions expressed from the cloned EcoRI.C fragment, two components have to be distinguished: one, a highly efficient elimination of plasmid DNA carrying the early Mu genes, and second, a series of interactions with host functions conducent to an inhibition of cell division. It is suggested that functions normally involved in the SOS reaction participate in the inhibition of cell division by early Mu functions. Infected bacteria synthesize the replication protein B (MR 33000) of Mu, which was found by cell fractionation experiments to be associated with the inner cell membrane. The role of this association for filamentous growth and for the integrative replication of the phage is discussed. The recombinant phage might be useful as a tool for the study of the E. coli cell division cycle.

Novel dimeric configurations from bacteriophage G4 replicative form DNA

The oligomeric fraction of the replicative form of phage G4 was prepared by sedimentation on three successive CsCl velocity gradients followed by resolution on CsCl-propidium diiodide equilibrium gradients and subfractions through the equilibrium gradients were examined by electron microscopy. The most frequent dimer species were the circular dimer, the singly linked catenane and the figure 8; these occurred in a ratio of 10:3:1. The high enrichment for dimers and other oligomers made possible the observation and the determination of the frequency of occurrence of a number of minor species, some of them of novel configuration. These are (a) dimers similar to figure 8s except containing long, apparently four-stranded junctions common to the two halves (theta forms); (2) dimers similar to those in (1) except that the long junctions separate the two halves (dumbbell forms); (3) multiply catenated dimers with apparent right-handed intertwines; and (4) dimers containing a knot. Theta forms cleaved by EcoRI were shown to be stable under conditions in which EcoRI-treated figure 8s were resolved by branch migration.

Assembly site of bacteriophage f1 corresponds to adhesion zones between the inner and outer membranes of the host cell

Morphogenesis of the filamentous bacteriophage f1 occurred at adhesion zones between the inner and outer membranes of the host cell. Quantitation of adhesion zones in cells infected with mutant phage strains suggested that the phage gene I protein may be involved in the formation of adhesion zones for phage assembly.

Morphogenetic structures present in lysates of amber mutants of bacteriophage Mu

The Mu phage particle is structurally similar to that of the T-even phages, consisting of an icosahedral head and contractile tail. This study continues an analysis of the morphogenesis of the Mu phage particle by defining the structural defects resulting from mutations in specific Mu genes. Defective lysates produced by induction of 55 amber mutants, representing 24 essential genes, were examined in the electron microscope and categorized into eight classes based on the observed phage-related structures. (1) Mutations in genes lys, F and G, and some H mutations, did not cause a visible alteration in particle structure. (2) Mutants defective in genes A, B, and C produced no detectable phage structures, consistent with their lack of production of late RNA. (3) Extracts defective in genes L, M, Y, N, P, Q, V, W, and R contained only head structures, and these appeared normal. (4) K-defective mutants accumulated free heads as well as free tails which were longer than normal and variable in length. (5) Tails which appeared normal were the only structures found in T- and some I-defective extracts. (6) Free tails and empty heads accumulated in D-, E-, and some I- and H-defective extracts. These heads were as much as 16% smaller than normal heads. The heads found in some I amber lysates had a protruding neck-like structure and unusually thick shells suggestive of a scaffolding-like structure. (7) Defects in gene J resulted in the accumulation of unattached tails and full heads. (8) Previous analysis of lysates produced by inversion-defective gin mutants fixed in the G(+) orientation demonstrated that S and U mutants produced particles lacking tail fibers (F.J. Grundy and M.M. Howe (1984), Virology 134, 296-317). In these experiments with Gin+ phages S and U mutants produced apparently normal phage particles. Presumably the tail fiber defects were masked by the production of S' and U' proteins by G(-) phages in the population.

Irreversible binding to the receptor of bacteriophages T5 and BF23 does not occur with the tip of the tail

Treatment of purified tails of bacteriophage T5 with 0.05% sodium dodecyl sulfate specifically removed pb2, a protein of 108,000 molecular weight (108K), from the tail. Although these tails were devoid of the single straight tail fiber, they still inhibited adsorption of T5 to Escherichia coli cells. Reconstitution of these tails with pb2 increased the efficiency of inhibition of T5 adsorption. Treatment of tails with 0.1% sodium dodecyl sulfate removed, in addition to pb2, a protein of 67K from phage T5 and one of 60K from phage BF23. These tails failed to inhibit phage adsorption, and no reconstitution was achieved. Reconstitution of T5 tails with pb2 from BF23, and of BF23 tails with pb2 from T5, did not alter the host receptor specificity of the tails. Binding of untreated T5 tails to small FhuA receptor particles revealed that binding occurred with the conical part of the tail and that pb2 was most likely released from the tail upon binding. From these results and from recent observations with T5-BF23 hybrid phages (K.J. Heller, Virology 139:11-21, 1984), we conclude that the receptor-binding proteins of T5 and BF23 are the 67K and 60K proteins, respectively, and that they are not located at the tip of the tail but rather at or near the site where the straight tail fiber is attached to the conical part of the tail.

Isolation and partial characterization of temperature bacteriophages from enteropathogenic strains of Escherichia coli 0111:K58

We report studies on ten strains of Escherichia coli 0111:K58 isolated from children with acute diarrhea. Our results show that these E. coli strains do not produce the pathogenic factors of enterotoxic E. coli (ETEC) and are lysogenic for phages belonging to two groups that differ for host range, kinetics of thermal inactivation, antigenicity and morphology. These data support the hypothesis that these phages may in vivo contribute to reduction of the number of common E. coli strains by lytic infection favouring the development of the enteropathogenic strain of E. coli.

Association of M13 I-forms and spheroids with lipid vesicles

Electron microscopy and density gradient centrifugation were used to demonstrate that the coat protein of M13 I-forms and spheroids, but not of filaments, can form some type of association with lipid vesicles in vitro. The association was detected only when the phage particles were incubated with dilauroylphosphatidylcholine (DLPC) or dimyristoylphosphatidylcholine (DMPC) small unilamellar vesicles (SUV) above the phase transition temperature of the lipid. Under these conditions the I-form coat protein was resistant to proteolytic digestion, and the viral DNA was also associated with the vesicles.

Identification of the phage gene for host receptor specificity by analyzing hybrid phages of T5 and BF23

The closely related coliphages T5 and BF23 differ in the receptor used for adsorption to cells. In order to identify phage genes encoding host receptor specificity, hybrid phages were isolated from crosses of T5 and BF23. These hybrid phages were analyzed for their protein composition, kinetics of adsorption to various bacterial strains, and DNA restriction maps. Analyses of the protein compositions of purified tails suggested that only one tail protein was involved in the expression of host specificity. In T5 tails this protein was identified as a minor tail protein of an apparent molecular weight of 67K. A corresponding BF23 protein could not be detected. The DNA region encoding structural proteins was analyzed by digestion with the restriction enzymes BamHI, HindIII, and PstI. The distribution of restriction sites in these recombinants implied that the region affecting host specificity was located at ca. 90% of the T5 genome length. Evidence is presented that this gene is identical to the oad gene previously described (K.J. Heller and D. Bryniok (1984), J. Virol. 49, 20-25). The location of other genes encoding tail proteins is discussed.

Production of a bacteriolysin by a hemolytic Escherichia coli strain

Nonhemolytic Escherichia coli were outnumbered by hemolytic E. coli within 24 h after being inoculated in a mixed culture at an initial ratio of 200 nonhemolytic to 1 hemolytic organism. The hemolytic strain was found to produce a cell-free, filterable substance which causes lysis of nonhemolytic E. coli B when grown in liquid cultures but not when grown on agar plates. The bacteriolysin is inactivated by boiling, by freezing and thawing, and by incubation with trypsin. The inability to inhibit growth on an agar plate, dependence on cell concentration for its effect, lysis of the sensitive cells, and appearance of phage particles in the cell lysates suggest that this substance is not like colicins or microcins previously described. After lysis of E. coli B, bacteriophage particles were visible in transmission electron micrographs of material pelleted by ultracentrifugation. However, no bacteriophage were observed in pellets from the bacteriolysin-containing supernatants before lysis of E. coli B. Failure to find bacteriophage in these preparations, and the fact that some bacteriolysin activity remains in the supernatant solution after centrifugation at 150,000 X g for 6.5 h, indicate that the bacteriolysin is not itself a bacteriophage. Exposure of E. coli B to UV light and mitomycin C did not induce production of a temperate phage. The properties of this system, in which a cell-free substance produced by one strain of bacteria causes lysis of another strain, appear to differ from those of the various types of bacteriocins and bacteriophages described to date.

DNA and protein lattice-lattice interactions in the filamentous bacteriophages

The relations between the protein coats and DNAs of the four filamentous bacteriophages fd, Xf, Pf1, and Pf3 are considered. These viruses have similar morphologies, yet show a diversity of detailed structure, having different protein coat symmetries (helical and rotational), different coat protein sizes (44-50 amino acids per subunit) and sequences, different nucleotide axial translations (2.3-5.5 A), and different ratios of nucleotides per coat protein subunit (integers 1.0 and 2.0, and nonintegers approximately 2.4). These divergences are all reconciled quantitatively by means of two theoretical concepts: the pitch connection and the restricted pitch connection. The pitch connection relates protein and DNA surface lattices with arbitrary, nonintegral nucleotide/subunit ratios in a nonrandom way. The restricted pitch connection selects a preferred set of n/s values. Both relations are derived formally in a mathematical appendix. The available structural data are explained, including the fd DNA pitch indicated by x-ray diffraction photos and the similar DNA morphologies of Xf and fd. Predictions are made for the existence of nonclassical inverted DNA structures (I-DNA) in Pf1 and Pf3.

Coat protein conformation in M13 filaments, I-forms and spheroids

Circular dichroism studies of the filamentous coliphage M13 were carried out to determine conformational changes in the major capsid protein (the B protein) that occur during contraction of the filaments to I-forms and spheroids. The alpha-helicity of the B protein is somewhat lower in the I-forms than in filaments and much lower in spheroids. This conformational change may explain the increased detergent and lipid solubility of both I forms and spheroids relative to filaments.

Sewage coliphages studied by electron microscopy

Sewage was enriched with 35 Escherichia coli strains, and sediments of enrichment cultures were studied in the electron microscope. They contained up to 10 varieties of morphologically different particles. T-even-type phages predominated in 14 samples. Thirteen phages were enriched, representing the families Myoviridae (seven), Styloviridae (two), Podoviridae (three), and Microviridae (one). Twelve of these corresponded to known enterobacterial phage species, namely, 121, K19, FC3-9, O1, 9266, T2, 16-19, kappa, beta 4, N4, T7, and phi X174. Cubic RNA phages and filamentous phages were not detected. Types 121 and 9266 have previously been observed only in Romania and South Africa. Identification by morphology is usually simple. Our investigative technique is qualitative and will not detect all phages present. Most enrichment strains are polyvalent, and electron microscopy is always required for phage identification. In a general way, electron microscopy seems to be the method of choice for investigation of phage geography and ecology.

Coliphage P1 morphogenesis: analysis of mutants by electron microscopy

We used electron microscopy and serum blocking power tests to determine the phenotypes of 47 phage P1 amber mutants that have defects in particle morphogenesis. Eleven mutants showed head defects, 30 showed tail defects, and 6 had a defect in particle maturation (which could be either in the head or in the tail). Consideration of previous complementation test results, genetic and physical positions of the mutations, and phenotypes of the mutants allowed assignment of most of the 47 mutations to genes. Thus, a minimum of 12 tail genes, 4 head genes, and 1 particle maturation gene are now known for P1. Of the 12 tail genes, 1 (gene 19, located within the invertible C loop) codes for tail fibers, 6 (genes 3, 5, 16, 20, 21, and 26) code for baseplate components (although one of these genes could code for the tail tube), 1 (gene 22) codes for the sheath, 1 (gene 6) affects tail length, 2 (genes 7 and 25) are involved in tail stability, and 1 (gene 24) either codes for a baseplate component or is involved in tail stability. Of the four head genes, gene 9 codes for a protein required for DNA packaging. The function of head gene 4 is unclear. Head gene 8 probably codes for a minor head protein, whereas head gene 23 could code for either a minor head protein or the major head protein. Excluding the particle maturation gene (gene 1), the 12 tail genes are clustered in three regions of the P1 physical genome. The four head genes are at four separate locations. However, some P1 head genes have not yet been detected and could be located in two regions (for which there are no known genes) adjacent to genes 4 and 8. The P1 morphogenetic gene clusters are interrupted by many genes that are expressed in the prophage.

Phages I alpha and I2-2: IncI plasmid-dependent bacteriophages

Phage I alpha was isolated from sewage from Windhoek, South West Africa. It formed relatively clear plaques about 2 mm in diameter, on sensitive strains of Escherichia coli K12 and Salmonella typhimurium LT2. The phage had an hexagonal outline with a diameter of about 24 nm, contained RNA and was resistant to chloroform. Phage I alpha formed plaques or propagated only on organisms carrying I1 plasmids or the I gamma plasmid R621a. The efficiency of plating was higher on E. coli than on S. typhimurium hosts. The phage adsorbed along the length of shafts of I1 pili. Phage I2-2 was isolated from Pretoria sewage. It was a filamentous virus and individual virions varied considerably in length. Phage I2-2 formed turbid plaques which varied from pin point to about 1 mm in diameter on all hosts. It was resistant to RNAase and sensitive to chloroform. Phage I2-2 had a spectrum of activity limited to strains harbouring I2 plasmids but the adsorption site could not be demonstrated. The phage was not related serologically to phages Ifl or PR64FS.

A comparison of the virucidal properties of chlorine, chlorine dioxide, bromine chloride and iodine

Chlorine dioxide, bromine chloride and iodine were compared with chlorine as virucidal agents. Under optimal conditions all disinfectants were effective at low concentrations, but each disinfectant responded differently to acidity and alkalinity. Disinfection by chlorine was impaired by the presence of ammonia, but the other disinfectants retained much of their potency. Disinfection of poliovirus by iodine resulted in structural changes in the virions as seen by electron micrroscopy, but the other disinfectants were able to inactivate poliovirus without causing any apparent structural changes.

Chemical evidence for the capsomeric structure of phage q beta

Novel capsomeric complexes, pentamers and hexamers were detected as chemical entities in phage Q beta. Both were composed of identical protein subunits and stabilized by intermolecular disulphide bonds. Their numbers per particle were about 12 for pentamers and about 20 for hexamers--consistent with theoretical expectation from the quasi-equivalent packing of 180 identical subunits in a coat protein shell.

Stability of Lambdoid bacteriophage heads: antagonism between polyamines and tryptamine

The biological activity of heads of bacteriophages phi 80 and lambda in in vitro assembly with tails was inhibited by dialysis, filtration on gels, and treatment with tryptamine. Inhibition by these three treatments could be prevented but not reversed by putrescine. Other diamines with shorter or longer carbon chain lengths were either less effective or not effective at all. It is suggested that tryptamine acts by loosening the tightly packed DNA in heads, whereas putrescine stabilizes it.

Endo-N-acetylneuraminidase associated with bacteriophage particles

A bacteriophage (phi 1.2) has been isolated for Escherichia coli K235 (O1:K1:H-). phi 1.2 is specific for the host capsular polysaccharide (colominic acid). The phage forms plaques with acapsular halos and thus carries a glycanase activity for colominic acid, a homopolymer of alpha (2 leads to 8)-linked N-acetylneuraminic acid (NeuNAc) residues. Upon incubation with purified phi 1.2 particles, a solution of K1 polysaccharide loses viscosity and consumes increasing amounts of periodate. Also, by gel filtration, the production of colominic oligosaccharides (down to a size of two to three NeuNAc residues) can be demonstrated. No NeuNAc monomers, however, are formed. The capsules of E. coli strains with the K92 antigen, which consists of NeuNAc residues linked by alternating alpha (2 leads to 8) and alpha (2 leads to 9) bonds, are also depolymerized by the phi 1.2 enzyme. Under the electron microscope, phage phi 1.2 is seen to belong to Bradley's morphology group C (D. E. Bradley, Bacteriol. Rev. 31:230-314, 1967); it has an isometric head, carrying a baseplate with six spikes. By analogy to other virus particles with host capsule depolymerase activity, it is probable that the phi 1.2 endo-N-acetylneuraminidase activity is associated with these spikes.

Minor coat protein composition and location of the A protein in bacteriophage f1 spheroids and I-forms

The filamentous bacteriophage f1 can be transformed into a spherical particle (spheroid) or an intermediate shortened filament with a flared end (I-forms) by exposure to a chloroform-water interface at 22 or 4 degrees C, respectively. The protein composition of bacteriophage f1 spheroids and I-forms was examined by separating the proteins from the purified. [35S]cysteine-labeled particles by sodium dodecyl sulfate-urea-polyacrylamide gel electrophoresis. Quantitation of the radioactivity on the gels showed that I-forms and spheroids contain the same complement of minor coat proteins as do untreated f1 phage. This composition is unchanged after removal of the DNA, either by digestion with micrococcal nuclease or by centrifugation of the particles through CsCl density gradients, indicating that none of the minor coat proteins is held in the particles solely through an interaction with the DNA. We also examined the location of the A protein in I-forms by decoration with ferritin-conjugated antibodies and examination under the electron microscope and found that the A protein is located specifically at the flared end of the I-form particle, through which the DNA is extruded and at which contraction into spheroids begins. The implications of these results with regard to the orientation of the DNA within the capsid and the process of infection are discussed.

19F nuclear magnetic resonance studies of the coat protein of bacteriophage M13 in synthetic phospholipid vesicles and deoxycholate micelles

The nonlytic, filamentous coliphage M13 offers an excellent model system for the study of membrane-protein interactions. We prepare derivatives of the protein containing fluorine-labeled amino acids and use 19F nuclear magnetic resonance (NMR) to study the protein in both deoxycholate micelles and phospholipid vesicles. We have previously described the in vivo preparation of an m-fluorotyrosyl derivative of M13 coat protein and also a method for incorporation of high levels of this protein into small, uniformly sized phospholipid vesicles of defined composition. Herein we describe the in vivo preparation and the characterization of an m-fluorophenylalanine derivative. We simultaneously compare the environment and mobility of the tyrosine and phenylalanine residues (the former in the hydrophobic region of the protein and the latter in the hydrophilic regions) as influenced by bile salt detergent or lipid interactions.

Filamentous phage pre-coat is an integral membrane protein: analysis by a new method of membrane preparation

We show, using a simple, rapid fractionation method, that the precursor to the filamentous phage major coat protein is an integral membrane protein. The method, which consists of treatment of Escherichia coli with 0.1 N NaOH followed by centrifugation, leaves a subset of inner and outer membrane proteins in the NaOH pellet. Most proteins partition into the NaOH pellet (membrane) or supernatant (cytoplasm and periplasm) in a manner consistent with their subcellular location as determined by more conventional techniques. We find no evidence for cytoplasmic filamentous phage pre-coat protein in either wild-type of mutant-infected cells. Our evidence suggests that a protein identified as "soluble procoat" by K. Ito, G. Mandell and W. Wickner may be the amber fragment of a different phage protein.