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1.
The nature of pteroyl polyglutamates in uninfected and T4D bacteriophage-infected Escherichia coli B has been examined. (3)H-p-aminobenzoic acid has been used to label the folate compounds and gel permeation chromatography on glass beads to separate the folate compound by molecular size. It has been found that, although the major folate compound in uninfected bacteria is pteroyl triglutamate, E. coli B cells also contain folate compounds having as many as six glutamate residues. Infection with T4D stimulated the addition of glutamate residues to the lower-molecular-weight host pteroyl compounds, resulting in the conversion of the host compounds into the hexaglutamate form. This viral-induced conversion is chloramphenicol sensitive and appears to be due to a late phage gene product. The phage gene responsible for this conversion has not been identified. In cells infected with a T4D mutant defective in gene 28, there was an apparent production of the large pteroyl polyglutamates equivalent in size to pte(glu)(9-12). These high-molecular-weight forms were converted into pte(glu)(6) by incubation with bacterial extracts made after infection with T4D 28(+). Apparently, the product of T4D gene 28(+) is capable of specifically cleaving the high-molecular-weight polyglutamates to the form necessary for phage tail assembly.  相似文献   

2.
Lysis Inhibition in Escherichia coli Infected with Bacteriophage T4   总被引:5,自引:5,他引:5       下载免费PDF全文
A technique of continuous filtration of T4-infected Escherichia coli has been devised to study the phenomenon of lysis inhibition. Studies using this technique revealed that the length of the lysis delay caused by superinfection can attain only certain discrete values, which for low average multiplicity of superinfection is thought to be a reflection of the actual number of superinfecting particles per cell. The time interval between primary and superinfection had little effect on the length of lysis delay. With increasing rate of superinfection, the length of lysis delay decreased. In superinfected cells, the concentration of endolysin exceeded the final concentration in nonsuperinfected cells. Superinfection of a lysing culture induced lysis inhibition immediately. Temperature-shift experiments, with cells primarily infected by a temperature-sensitive endolysin mutant, revealed that after the normal latent period superinfection was unable to induce lysis inhibition. Amber-restrictive cells, which were primarily infected by an endolysin negative amber mutant, released adenosine triphosphate (ATP) at the end of the normal latent period although lysis did not occur. Superinfection reduced the loss of ATP markedly. The hypothetical role of the cytoplasmic membrane in lysis inhibition is discussed.  相似文献   

3.
An Escherichia coli K-12 biofilm was grown at a dilution rate of 0.028 h(-1) for 48 h in a glucose-limited chemostat coupled to a modified Robbins' device to determine its susceptibility to infection by bacteriophage T4. Bacteriophage T4 at a multiplicity of infection (MOI) of 10 caused a log reduction in biofilm density (expressed as colony forming units (CFU) per cm2) at 90 min postinfection. After 6 h, a net decrease and equilibrium in viral titer was seen. When biofilms were exposed to T4 phage at a MOI of 100, viral titer doubled after 90 min. After 6 h, viral titers (expressed as plaque forming units (PFU) per cm2) stabilized at levels approximately one order of magnitude higher than seen at a MOI of 10. Scanning confocal laser microscopy images also indicated disruption of biofilm morphology following T4 infection with the effects being more pronounced at a MOI of 100 than at a MOI of 10. These results imply that biofilms under carbon limitation can act as natural reservoirs for bacteriophage and that bacteriophage can have some influence on biofilm morphology.  相似文献   

4.
Three independent parameters (eclipse and latent periods, and rate of ripening during the rise period) are essential and sufficient to describe bacteriophage development in its bacterial host. A general model to describe the classical "one-step growth" experiment [Rabinovitch et al. (1999a) J. Bacteriol.181, 1687-1683] allowed their calculations from experimental results obtained with T4 in Escherichia coli B/r under different growth conditions [Hadas et al. (1997) Microbiology143, 179-185]. It is found that all three parameters could be described by their dependence solely on the culture doubling time tau before infection. Their functional dependence on tau, derived by a best-fit analysis, was used to calculate burst size values. The latter agree well with the experimental results. The dependence of the derived parameters on growth conditions can be used to predict phage development under other experimental manipulations.  相似文献   

5.
Hydroxyurea inhibited the replication of bacteriophage T4 in Escherichia coli B. The concentration of hydroxyurea required to inhibit net deoxyribonucleic acid (DNA) synthesis 50% was about 50-fold less than that required in uninfected cells. Even in the presence of high hydroxyurea concentrations, phage DNA was readily synthesized from the products of breakdown of the E. coli DNA, and viable phage were made. Deoxyribonucleotide, but not ribonucleotide, synthesis was strongly inhibited in the presence of hydroxyurea. The data indicate that hydroxyurea specifically inhibits de novo DNA synthesis in E. coli infected with bacteriophage T4 by inhibiting the ribonucleoside diphosphate reductase system, but does not affect DNA synthesis at subsequent steps.  相似文献   

6.
Hydrolysis of phospholipids was observed to start about 15 min after Escherichia coli S/6 cells were infected with T4rII bacteriophage mutants. Hydrolysis continued through the latent period and well past the time when cell lysis occurs. The hydrolytic products that accumulated were free fatty acids, 2-acyl lysophosphatidylethanolamine, and various lysocardiolipins. These products indicated the action of phospholipase A(1). From 15 to 22 min after infection, there were equivalent amounts of fatty acids and lysophosphatides in extracts of cellular lipids. Thereafter, free fatty acids were produced in excess. This suggests that lysophospholipase was active at the later time. We also observed a stoichiometric relation between loss of phosphatidylglycerol and increase of cardiolipin plus lysocardiolipins. This continued well past the normal lysis time (25 min). The appearance of lipase activities during the latent period seems to be specific to infection with rII mutants. Neither the wild-type bacteriophage nor rI mutants produced similar activities by 22 min after infection.  相似文献   

7.
A mutant of Escherichia coli B, defective in its accumulation of K+, was found to synthesize protein at a rate proportional to the level of this cation in the growth medium. When bacteriophage T4-infected cells were incubated in growth medium containing 1 mm K+, phage deoxyribonucleic acid (DNA) was synthesized at a rate 25% that of normal, and phage protein was synthesized at a rate of 50% of normal. Deoxycytidine pyrophosphatase, a phage-directed early enzyme, shut off at a level of 55% that of normal when infected cells were incubated in medium containing 1 mm K+. However, deoxycytidine pyrophosphatase synthesis resumed in these cells when they were shifted to medium containing the normal K+ concentration (33 mm). DNA synthesis also attained the rate characteristic of this K+ concentration. These results suggest that phage DNA synthesis is not sufficient to repress early protein formation and also indicate that the inhibitor of early protein formation is an early function whose synthesis is sensitive to the same repression as that of the early proteins.  相似文献   

8.
Genetic evidence for site- and gene-specific variation in limited heterocatalytic expression in phage T4-infected Escherichia coli is reported, and the implications of such variation are discussed.  相似文献   

9.
The folded genome of Escherichia coli is converted to a slower-sedimenting form within 5 min after infection with bacteriophage T4 or T4nd28(den A)-amN82(44). Chloramphenicol sensitivity and response to UV-irradiation of the phage suggest participation of viral-induced functions.  相似文献   

10.
The protein component of the T-even bacteriophage coat which binds the phage-specific dihydropteroyl polyglutamate has been identified as the phage-induced dihydrofolate reductase. Dihydrofolate reductase activity has been found in highly purified preparations of T-even phage ghosts and phage substructures after partial denaturation. The highest specific enzymatic activity was found in purified tail plate preparations, and it was concluded that this enzyme was a structural component of the phage tail plate. Phage viability was directly correlated with the enzymological properties of the phage tail plate dihydrofolate reductase. All reactions catalyzed by this enzyme which changed the oxidation state of the phage dihydrofolate also inactivated the phage. Properties of two T4D dihydrofolate reductase-negative mutants, wh1 and wh11, have been examined. Various lines of evidence support the view that the product of the wh locus of the phage genome is normally incorporated into the phage tail structure. The effects of various dihydrofolate reductase inhibitors on phage assembly in in vitro complementation experiments with various extracts of conditional lethal T4D mutants have been examined. These inhibitors were found to specifically block complementation when added to extracts which did not contain preformed tail plates. If tail plates were present, inhibitors such as aminopterin, did not affect further phage assembly. This specific inhibition of tail plate formation in vitro confirms the analytical and genetic evidence that this phage-induced "early" enzyme is a component of the phage coat.  相似文献   

11.
Exposure of Escherichia coli cells to myxin results in the almost complete inhibition of new deoxyribonucleic acid (DNA) synthesis, extensive degradation of pre-existing intracellular DNA, and a rapid loss of viability in these cells (9). After exposure to myxin for 30 min (<1% survivors and >25% degradation of DNA), infection of these cells by T4 bacteriophage results in the renewal of DNA synthesis at a rate essentially equal to that found in T4-infected cells in the absence of myxin. This DNA was characterized as T4 DNA by hybridization and by hydroxyapatite chromatography. These results suggest that the primary site of action of myxin does not involve the biochemical pathways involved in either the energy metabolism or the biosynthesis of DNA precursors in the uninfected host cell. The yield of infectious T4 particles was reduced when myxin was present during multiplication. This effect may be partly accounted for by the finding that a significant fraction of the T4 DNA synthesized in the presence of myxin is apparently not properly enclosed by the bacteriophage protein coat since it is shown to be degraded by exogenous nuclease.  相似文献   

12.
We investigated the synthesis of DNA in toluene-treated cells prepared from Escherichia coli infected with bacteriophage T4. If the phage carry certain rII deletion mutations, those which extend into the nearby D2a region, the following results are obtained: (i) phage DNA synthesis occurs unless the phage carries certain DNA-negative mutations; and (ii) host DNA synthesis occurs even though the phage infection has already resulted in the cessation of host DNA synthesis in vivo. The latter result indicates that the phage-induced cessation of host DNA synthesis is not due to an irreversible inactivation of an essential component of the replication apparatus. If the phage are D2a(+), host DNA synthesis in toluene-treated infected cells is markedly reduced; phage DNA synthesis is probably also reduced somewhat. These D2a effects, considered along with our earlier work, suggest that a D2a-controlled nuclease, specific for cytosine-containing DNA, is active in toluene-treated cells.  相似文献   

13.
14.
Isolation of the Bacteriophage Lambda Receptor from Escherichia coli   总被引:30,自引:49,他引:30       下载免费PDF全文
A factor which inactivates the phage lambda can be extracted from Escherichia coli. This factor is a protein and is located in the outer membrane of the bacterial envelope. It is found in extracts of strains which are sensitive to phage lambda, but not in extracts of strains specifically resistant to this phage. We conclude that this factor is the lambda receptor, responsible for the specific adsorption of the phage lambda to E. coli cells. A partial purification of the lambda receptor is described. Inactivation of the phage by purified receptor is shown to be accompanied by the release of deoxyribonucleic acid from the phage.  相似文献   

15.
We have presented a new approach to studying bacteriophage T4 head maturation. Using a modified M-band technique, we have shown that progeny deoxyribonucleic acid (DNA) was synthesized on the host cell membrane throughout infection. This DNA was released from the membrane later in infection as the result of formation of the phage head; detachment of the DNA required the action of gene products 20, 21, 22, 23, 24, 31, 16, 17 and 49, known to be necessary for normal head formation. Gene products 2, 4, 50, 64, 65, 13 and 14, also involved in head morphogenesis were not required to detach progeny DNA from the membrane; the presence of the phage tail and tail fibers also was not required. DNA was released in the form of immature heads and initially was sensitive to deoxyribonuclease (DNase). Conversion to DNase resistance followed rapidly. The amount of phage precursors present at the time of DNA synthesis determined the time of onset and detachment rate of DNA from the M band as well as the kinetics by which the detached DNA become DNase resistant.  相似文献   

16.
T7 phage resists Escherichia coli B host-controlled modification and restriction in vivo, but its DNA carries roughly five sites which are susceptible to the purified enzymes.  相似文献   

17.
Escherichia coli mutants have been isolated that are permissive for the infection by T4 phage with deletion in the cistron for the phage lysozyme, the e gene. Some, but not all, of these mutants are simultaneously permissive for the infection by T4 phage defective in the t gene, the product of which has also been implicated in the release of progeny phages. Most of these mutants shared the following properties: temperature sensitivity in growth and cell division, increased sensitivity towards a number of unrelated antibiotics and colicins, and increased sensitivity towards anionic detergents (sodium dodecyl sulfate and sodium deoxycholate). The possible biochemical basis for these phenotypes is discussed.  相似文献   

18.
Bacteriophage T4 Genome   总被引:10,自引:0,他引:10       下载免费PDF全文
  相似文献   

19.
20.
Urinary strains of Escherichia coli from seven geographical regions were typed serologically for O-specific antigens and with phages capable of lysing the majority of urinary isolated. The O antigen groups 4, 6, 75, 1, 50, 7, and 25 were the common ones found. Of the 454 cultures tested, 66.1% were phage typable and 65.2% were serotypable with the 48 antisera employed. Also, 71.6% of the cultures for which an O group could be determined were phage typable. Furthermore, of those seven O-antigen groups implicated in urinary tract infection, 80.2% exhibited a phage pattern. Various phage types were found within an O-antigen group, and, although one phage type associated a high percentage of the time with one O-antigen group, no correlation was observed between other O-antigen groups and phage types. Studies with bacteriuric patients by phage typing showed the presence of two strains of E. coli within an O-antigen group. Serogrouping and phage typing of fecal isolates of E. coli revealed the presence of some O-antigen groups and phage types also found as predominant types among urinary isolates. Phage typability correlated highly with hemolysis of human erythrocytes. Elevated temperatures of incubation and a chemical curing agent were used to enhance typability of cultures refractory to the typing phages. Phage typing, due to its rapidity, ease, and ability to distinguish strains of E. coli within an O-antigenic group, is suggested as a possible method by which a better insight into the epidemiology of urinary tract infections may be obtained.  相似文献   

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