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1.
Pasteurella pestis Bacteriophage H and Escherichia coli Bacteriophage φII Are Nearly Identical
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Electron microscopy examination of II-H deoxyribonucleic acid heteroduplexes, together with polyacrylamide gel electrophoretic analyses of phage ribonucleic acid species and proteins labeled in II or H-infected cells, demonstrates that Pasteurella pestis phage H is nearly identical to coliphage II. 相似文献
2.
The temperate bacteriophage adh mediates plasmid DNA transduction in Lactobacillus gasseri ADH at frequencies in the range of 10-8 to 10-10 transductants per PFU. BglII-generated DNA fragments from phage adh were cloned into the BclI site of the transducible plasmid vector pGK12 (4.4 kb). Phage adh lysates induced from Lactobacillus lysogens harboring pGK12 or the recombinant plasmids were used to transduce strain ADH to chloramphenicol resistance. The transduction frequencies of recombinant plasmids were 102- to 105-fold higher than that of native pGK12. The increase in frequency generally correlated with the extent of DNA-DNA homology between plasmid and phage DNAs. The highest transduction frequency was obtained with plasmid pTRK170 (6.6 kb), a pGK12 derivative containing the 1.4- and 0.8-kb BglII DNA fragments of adh. DNA hybridization analysis of pTRK170-transducing phage particles revealed that pTRK170 had integrated into the adh genome, suggesting that recombination between homologous sequences present in phage and plasmid DNAs was responsible for the formation of high-frequency transducing phage particles. Plasmid DNA analysis of 13 transductants containing pTRK170 showed that each had acquired intact plasmids, indicating that in the process of transduction a further recombination step was involved in the resolution of plasmid DNA monomers from the recombinant pTRK170::adh molecule. In addition to strain ADH, pTRK170 could be transduced via adh to eight different L. gasseri strains, including the neotype strain, F. Gasser 63 AM (ATCC 33323). 相似文献
3.
Influence of Bacteriophage PBS1 and φW-14 Deoxyribonucleic Acids on Homologous Deoxyribonucleic Acid Uptake and Transformation in Competent Bacillus subtilis
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Paloma Lpez Manuel Espinosa Mirosawa Piechowska David Shugar 《Journal of bacteriology》1980,143(1):50-58
Both bacteriophage PBS1 deoxyribonucleic acid (DNA) (in which all the thymine residues are replaced by uracil) and phage W-14 DNA [in which half the thymine residues are replaced by 5-(aminobutylaminomethyl)uracil or 5-putrescinylthymine] exhibit comparable competing abilities for uptake of homologous DNA in a Bacillus subtilis competent system. But, whereas PBS1 DNA leads to a decrease in transformation frequencies compatible with its competing ability for DNA uptake, W-14 DNA decreases transformation frequencies by a factor up to eightfold higher. The effect of W-14 DNA on transformation frequencies is visible even at a concentration level that does not decrease transforming DNA uptake. No such effect was observed with heterologous DNA containing presumably ionically bound putrescine. Low concentrations of W-14 DNA decreased the number of double (nonlinked) transformants more than single transformants. The influence on transformation was abolished when W-14 DNA was added 20 min after addition of transforming DNA, i.e., when the recombination process was terminated. The putrescine-containing DNA also decreased retention of trichloroacetic acid-precipitable radioactivity of homologous DNA taken up. We conclude that W-14 DNA inhibits some intracellular process(es) at the level of recombination. In addition, there is evidence that W-14 DNA, but not heterologous DNA with ionically bound putrescine, binds also to site(s) on the cell surface other than receptors for homologous DNA. 相似文献
4.
Prophage Origin of a Virulent Phage Appearing on Fermentations of Lactobacillus casei S-1 总被引:13,自引:9,他引:4
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For protection from the abnormal fermentation of Lactobacillus casei S-1 caused by contamination of a virulent phage, FSV, the origin of this phage was studied. Morphologies, viral structural proteins, and DNA structures of three independent isolates of FSV were compared with those of FSW, which is lysogenized in strain S-1. The results showed (i) that the morphology of FSV phages is indistinguishable from that of FSW and (ii) that all viral structural components found in FSW are present in the particles of FSV's. In addition, restriction endonuclease analyses of viral DNA showed that the HindIII-digested fragments of FSW DNA, the sum of which covered at least 94.7% of this phage genome, were conserved in the FSV DNA digests. Results of Southern filter hybridization of the S-1 and prophage-cured cell (C239) DNAs with FSV DNA as a probe revealed that C239 had lost most of the FSV DNA sequence, whereas S-1 had about one copy of the FSV DNA sequence. These results indicate that virulent phage FSV is derived from the lysogenized phage FSW. Therefore, the appearance of FSV can be eliminated by using the prophage-cured derivative of S-1. 相似文献
5.
Interaction between Light Quality and Light Quantity in the Photoregulation of Anthocyanin Production 总被引:7,自引:2,他引:5
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Mancinelli AL 《Plant physiology》1990,92(4):1191-1195
The interaction between phytochrome photoequilibrium () and photon flux in the photoregulation of anthocyanin production under prolonged irradiation was studied in seedlings of Brassica oleracea L. and Lycopersicon esculentum Mill. In cabbage, anthocyanin production increases with decreasing , reaching a maximum at the lowest value ( = 0.13) used in this study; in tomato, the extent of the response is higher at intermediate values, reaching a maximum at = 0.46. In cabbage, the response increases with increasing photon flux at all values; however, the response to changes in photon flux is minimal at = 0.85, and, at = 0.13, minimal at photon fluxes higher than 5 micromolar per square meter per second. In tomato, the response increases with increasing photon flux at = 0.46, 0.65, and 0.85, the response to changes in photon fluxes being minimal at = 0.85; at = 0.13 and 0.29 the response first increases (significantly at = 0.29 and minimally at = 0.13) and then decreases with increasing photon fluxes, the transition occurring at about 1 micromolar per square meter per second at = 0.13, and at 5 micromolar per square meter per second at = 0.29. The patterns of light quality-quantity interaction in the photoregulation of anthocyanin production are significantly different in cabbage and tomato and are also significantly different than those observed for other photomorphogenic responses to prolonged irradiations. 相似文献
6.
Isolation and Characterization of Five Erwinia amylovora Bacteriophages and Assessment of Phage Resistance in Strains of Erwinia amylovora
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Phages able to infect the fire blight pathogen Erwinia amylovora were isolated from apple, pear, and raspberry tissues and from soil samples collected at sites displaying fire blight symptoms. Among a collection of 50 phage isolates, 5 distinct phages, including relatives of the previously described phages Ea1 and Ea7 and 3 novel phages named Ea100, Ea125, and Ea116C, were identified based on differences in genome size and restriction fragment pattern. Ea1, the phage distributed most widely, had an approximately 46-kb genome which exhibited some restriction site variability between isolates. Phages Ea100, Ea7, and Ea125 each had genomes of approximately 35 kb and could be distinguished by their EcoRI restriction fragment patterns. Ea116C contained an approximately 75-kb genome. Ea1, Ea7, Ea100, Ea125, and Ea116C were able to infect 39, 36, 16, 20, and 40, respectively, of 40 E. amylovora strains isolated from apple orchards in Michigan and 8, 12, 10, 10, and 12, respectively, of 12 E. amylovora strains isolated from raspberry fields (Rubus spp.) in Michigan. Only 22 of 52 strains were sensitive to all five phages, and 23 strains exhibited resistance to more than one phage. Ea116C was more effective than the other phages at lysing E. amylovora strain Ea110 in liquid culture, reducing the final titer of Ea110 by >95% when added at a ratio of 1 PFU per 10 CFU and by 58 to 90% at 1 PFU per 105 CFU. 相似文献
7.
DNA replication of 29 and related phages takes place via a strand displacement mechanism, a process that generates large amounts of single-stranded DNA (ssDNA). Consequently, phage-encoded ssDNA-binding proteins (SSBs) are essential proteins during phage 29-like DNA replication. In the present work we analyze the helix-destabilizing activity of the SSBs of 29 and the related phages Nf and GA-1, their ability to eliminate non-productive binding of 29 DNA polymerase to ssDNA and their stimulatory effect on replication by 29 DNA polymerase in primed M13 ssDNA replication, a situation that resembles type II replicative intermediates that occur during 29-like DNA replication. Significant differences have been appreciated in the functional behavior of the three SSBs. First, the GA-1 SSB is able to display helix-destabilizing activity and to stimulate dNTP incorporation by 29 DNA polymerase in the M13 DNA replication assay, even at SSB concentrations at which the 29 and Nf SSBs do not show any effect. On the other hand, the 29 SSB is the only one of the three SSBs able to increase the replication rate of 29 DNA polymerase in primed M13 ssDNA replication. From the fact that the 29 SSB, but not the Nf SSB, stimulates the replication rate of Nf DNA polymerase we conclude that the different behaviors of the SSBs on stimulation of the replication rate of 29 and Nf DNA polymerases is most likely due to formation of different nucleoprotein complexes of the SSBs with the ssDNA rather than to a specific interaction between the SSB and the corresponding DNA polymerase. A model that correlates the thermodynamic parameters that define SSB–ssDNA nucleoprotein complex formation with the functional stimulatory effect of the SSB on 29-like DNA replication has been proposed. 相似文献
8.
Molecular Characterization of Three Small Isometric-Headed Bacteriophages Which Vary in Their Sensitivity to the Lactococcal Phage Resistance Plasmid pTR2030 总被引:6,自引:17,他引:6
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Lactococcus lactis LMA12-4 is a pTR2030 transconjugant that has been used as an industrial starter culture because of its resistance to phages predominant in cheese plants. Plasmid pTR2030 interferes with susceptible phages in this host strain via two mechanisms, restriction and modification (R/M) and abortive infection (Hsp). After prolonged use of LMA12-4 transconjugants in the industry, two different bacteriophages, designated nck202.48 (48) and nck202.50 (50), were isolated which could produce plaques on LMA12-4 containing pTR2030. In this study, these two phages were characterized and compared with a third phage, nck202.31 (31), which is susceptible to both the R/M and Hsp activities encoded by pTR2030. Phage 48 was not susceptible to inhibition by Hsp, whereas 50 was unaffected by either the R/M or Hsp mechanisms. All three were small isometric-headed phages, but small differences were noted between the phages in the structural details of the tail base plate, susceptibility to chloroform treatment, and requirements for calcium infectivity. The phage genomes were all between 29.9 and 31.9 kb in length. Phages 31 and 48 harbored cohesive ends, whereas the phage 50 genome was circularly permuted, terminally redundant, and carried a putative packaging initiation site. DNA-DNA hybridization experiments conducted between the phages revealed a common region in 48 and 50 that may correlate with the resistance of the two phages to the Hsp-abortive infection induced by pTR2030. Phage 50 also harbored DNA sequences that shared homology to pTR2030 in the region where R/M activities have been localized on the plasmid. Molecular characterization of the three phages localized regions within the genomes of the pTR2030-resistant phages that may be responsible for circumventing plasmid-encoded Hsp and R/M defense mechanisms in lactococci. 相似文献
9.
The lack of information on bacteriophages of Clostridium difficile prompted this study. Three of 56 clinical C. difficile isolates yielded double-stranded DNA phages C2, C5, C6, and C8 upon induction. Superinfection and DNA analyses revealed relatedness between the phages, while partial sequencing of C2 showed nucleotide homology to the sequenced C. difficile strain CD630. 相似文献
10.
RSA1 is a wide-host-range bacteriophage isolated from Ralstonia solanacearum. In this study, the complete nucleotide sequence of the RSA1 genomic DNA was determined. The genome was 38,760 bp of double-stranded DNA (65.3% G+C) with 19-bp 5′-extruding cohesive ends (cos) and contained 51 open reading frames (ORFs). Two-thirds of the RSA1 genomic region encodes the phage structural modules, and they are very similar to those reported for coliphage P2 and P2-like phages. A RSA1 minireplicon with an 8.2-kbp early-expressing region was constructed. A late-expression promoter sequence motif was predicted for these RSA1 genes as 5′ TGTTGT-(X)13-ACAACA. The genomic sequence similarity between RSA1 and related phages 52237 and CTX was interrupted by three AT islands, one of which contained an insertion sequence element, suggesting that they were recombinational hot spots. RSA1 was found to be integrated into at least three different strains of R. solanacearum, and the chromosomal integration site (attB) was identified as the 3′ portion of the arginine tRNA(CCG) gene. In the light of the RSA1 gene arrangement, one possible prophage sequence previously detected on the chromosome of R. solanacearum strain GMI1000 was characterized as a RSA1-related prophage (designated RSX). RSX was found to be integrated at the serine tRNA (GGA) gene as an att site, and its size was determined to be 40,713 bp. RSX ORFs shared very high amino acid identity with their RSA1 counterparts. The relationships and evolution of these P2-like phages are discussed. 相似文献
11.
Temperate Bacillus phage 105 is serologically unrelated to previously described virulent Bacillus phages. Phage 105 is incapable of generalized transduction. Prophage 105 is inducible with mitomycin C. Phage 105 contains double-stranded deoxyribonucleic acid (DNA) with a molecular weight of about 25 × 107 as determined by band sedimentation and electron microscopy. The per cent guanine plus cytosine of 105 DNA is 43.5 as determined by buoyant density in CsCl and by thermal denaturation. Phage 105 DNA may contain complementary single-stranded ends. 相似文献
12.
Paul E. Turner Christina L. Burch Kathryn A. Hanley Lin Chao 《Journal of virology》1999,73(3):2420-2424
Coinfection of the same host cell by multiple viruses may lead to increased competition for limited cellular resources, thus reducing the fitness of an individual virus. Selection should favor viruses that can limit or prevent coinfection, and it is not surprising that many viruses have evolved mechanisms to do so. Here we explore whether coinfection is limited in the RNA bacteriophage 6 that infects Pseudomonas phaseolicola. We estimated the limit to coinfection in 6 by comparing the frequency of hybrids produced by two marked phage strains to that predicted by a mathematical model based on differing limits to coinfection. Our results provide an alternative method for estimating the limit to coinfection and confirm a previous estimate between two to three phages per host cell. In addition, our data reveal that the rate of coinfection at low phage densities may exceed that expected through random Poisson sampling. We discuss whether phage 6 has evolved an optimal limit that balances the costly and beneficial fitness effects associated with multiple infections. 相似文献
13.
Genome coverage and sequence fidelity of φ29 polymerase-based multiple strand displacement whole genome amplification
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J. Guillermo Paez Ming Lin Rameen Beroukhim Jeffrey C. Lee Xiaojun Zhao Daniel J. Richter Stacey Gabriel Paula Herman Hidefumi Sasaki David Altshuler Cheng Li Matthew Meyerson William R. Sellers 《Nucleic acids research》2004,32(9):e71
Major efforts are underway to systematically define the somatic and germline genetic variations causally associated with disease. Genome-wide genetic analysis of actual clinical samples is, however, limited by the paucity of genomic DNA available. Here we have tested the fidelity and genome representation of 29 polymerase-based genome amplification (29MDA) using direct sequencing and high density oligonucleotide arrays probing >10000 SNP alleles. Genome representation was comprehensive and estimated to be 99.82% complete, although six regions encompassing a maximum of 5.62 Mb failed to amplify. There was no degradation in the accuracy of SNP genotyping and, in direct sequencing experiments sampling 500 000 bp, the estimated error rate (9.5 × 10–6) was the same as in paired unamplified samples. The detection of cancer-associated loss of heterozygosity and copy number changes, including homozygous deletion and gene amplification, were similarly robust. These results suggest that 29MDA yields high fidelity, near-complete genome representation suitable for high resolution genetic analysis. 相似文献
14.
Photocontrol of Hypocotyl Elongation in Light-Grown Cucumis sativus L. : Responses to Phytochrome Photostationary State and Fluence Rate 总被引:2,自引:2,他引:0
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The effects of the calculated photostationary state of phytochrome (c) and the photon fluence rate on the elongation growth of the hypocotyl of light-grown seedlings of Cucumis sativus L. are examined. Two threshold responses to c are found at values of 0.06 and 0.43. At c = 0.06, there is no response at any fluence rate. In the c range 0.1 to 0.43, elongation growth does not respond to changes in c. Above the second threshold (c = 0.43), there is a strong response to changes in c. At all values of c at and above 0.1, there is a response to fluence rate. A linear relationship can be demonstrated between a factor comprised of the logarithm of phytochrome cycling rate (a fluence-rate-dependent process) and c, and the growth response. 相似文献
15.
Anthony J. Garro 《Journal of virology》1973,12(1):18-24
Prophage was induced when strains of Bacillus subtilis 168 lysogenic for 105c4 were grown to competence and exposed to specific bacterial DNAs. The time course of phage production was similar to that observed for mitomycin C induction of wild-type prophage. Induction was directly dependent upon DNA concentration up to levels which were saturating for the transformation of bacterial auxotrophic markers. The extent of induction varied with the source of DNA. The burst of phage induced by DNA isolated from a W23 strain of B. subtilis was fivefold less than that induced by DNA from B. subtilis 168 strains, while B. licheniformis DNA was completely inactive. This order of inducing activity was correlated with the ability of the respective DNAs to transform auxotrophic markers carried by one of the 105c4 lysogens. Differences in inducing activity also were observed for different forms of 105 DNA. The DNAs isolated from 105 phage particles and 105c4 lysogens were inactive, whereas DNA from cells lysogenized by wild-type 105 induced a burst of phage. When tested for transforming activity, however, both 105c4 and 105 lysogen DNAs were equally effective. An induction mechanism which involves recombination at the prophage insertion site is proposed to explain these differences. 相似文献
16.
Translation of the bacteriophage X174 genome follows cistron order D-E-F-G-H-A-B-C. To establish this, the position of a nonsense mutation on the genetic map was compared with the physical size (molecular weight) of the appropriate protein fragment generated in nonpermissive cells. Distances on the X174 genetic map and distances on a physical map constructed from the molecular weights of X174 proteins and protein fragments are proportional over most of the genome with the exception of the high recombination region within cistron A. 相似文献
17.
Effects of Diverse Environmental Conditions on φLC3 Prophage Stability in Lactococcus lactis
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Merete Lunde Are Halvor Aastveit Janet Martha Blatny Ingolf F. Nes 《Applied microbiology》2005,71(2):721-727
The effects of various growth conditions on spontaneous LC3 prophage induction in Lactococcus lactis subsp. cremoris IMN-C1814 was analyzed with a half fraction of a 44 factorial experimental design. The four factors included in the study were nutrient availability, acidity, osmolarity, and temperature, each applied at four levels. These environmental factors are related to the fermentation processes in the dairy industry, in which bacteriophage attacks on sensitive starter strains are a constant threat to successful fermentation processes. The frequency of spontaneous LC3 induction was determined by quantitative analyses of restored DNA attachment sites (attB) on the bacterial chromosomes in a population of lysogenic cells. Statistical analysis revealed that all four environmental factors tested affected LC3 prophage stability and that the environmental factors were involved in interactions (interactions exist when the effect of one factor depends on the level of another factor). The spontaneous LC3 induction frequency varied from 0.08 to 1.76%. In general, the induction frequency remained at the same rate or decreased when level 1 to 3 of the four environmental factors was applied. At level 4, which generally gave the least favorable growth conditions, the induction frequency was either unchanged, decreased, or increased, depending on the type of stress. It appeared that the spontaneous induction frequency was independent of the growth behavior of the host. It was the environmental growth conditions that were the decisive factor in induction frequency. 相似文献
18.
Use of Real-Time Quantitative PCR for the Analysis of φLC3 Prophage Stability in Lactococci
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Merete Lunde Janet Martha Blatny Dag Lillehaug Are Halvor Aastveit Ingolf F. Nes 《Applied microbiology》2003,69(1):41-48
Bacteriophages are a common and constant threat to proper milk fermentation. It has become evident that lysogeny is widespread in lactic acid bacteria, and in this work the temperate lactococcal bacteriophage LC3 was used as a model to study prophage stability in lactococci. The stability was analyzed in six LC3 lysogenic Lactococcus lactis subsp. cremoris host strains when they were growing at 15 and 30°C. In order to perform these analyses, a real-time PCR assay was developed. The stability of the LC3 prophage was found to vary with the growth phase of its host L. lactis IMN-C1814, in which the induction rate increased during the exponential growth phase and reached a maximum level when the strain was entering the stationary phase. The maximum spontaneous induction frequency of the LC3 prophage varied between 0.32 and 9.1% (28-fold) in the six lysogenic strains. No correlation was observed between growth rates of the host cells and the spontaneous prophage induction frequencies. Furthermore, the level of extrachromosomal phage DNA after induction of the prophage varied between the strains (1.9 to 390%), and the estimated burst sizes varied up to eightfold. These results show that the host cells have a significant impact on the lytic and lysogenic life styles of temperate bacteriophages. The present study shows the power of the real-time PCR technique in the analysis of temperate phage biology and will be useful in work to reveal the impact of temperate phages and lysogenic bacteria in various ecological fields. 相似文献
19.
Genetic Analysis of Chromosomal Regions of Lactococcus lactis Acquired by Recombinant Lytic Phages
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Recombinant phages are generated when Lactococcus lactis subsp. lactis harboring plasmids encoding the abortive type (Abi) of phage resistance mechanisms is infected with small isometric phages belonging to the P335 species. These phage variants are likely to be an important source of virulent new phages that appear in dairy fermentations. They are distinguished from their progenitors by resistance to Abi defenses and by altered genome organization, including regions of L. lactis chromosomal DNA. The objective of this study was to characterize four recombinant variants that arose from infection of L. lactis NCK203 (Abi+) with phage 31. HindIII restriction maps of the variants (31.1, 31.2, 31.7, and 31.8) were generated, and these maps revealed the regions containing recombinant DNA. The recombinant region of phage 31.1, the variant that occurred most frequently, was sequenced and revealed 7.8 kb of new DNA compared with the parent phage, 31. This region contained numerous instances of homology with various lactococcal temperate phages, as well as homologues of the lambda recombination protein BET and Escherichia coli Holliday junction resolvase Rus, factors which may contribute to efficient recombination processes. A sequence analysis and phenotypic tests revealed a new origin of replication in the 31.1 DNA, which replaced the 31 origin. Three separate HindIII fragments, accounting for most of the recombinant region of 31.1, were separately cloned into gram-positive suicide vector pTRK333 and transformed into NCK203. Chromosomal insertions of each plasmid prevented the appearance of different combinations of recombinant phages. The chromosomal insertions did not affect an inducible prophage present in NCK203. Our results demonstrated that recombinant phages can acquire DNA cassettes from different regions of the chromosome in order to overcome Abi defenses. Disruption of these regions by insertion can alter the types and diversity of new phages that appear during phage-host interactions. 相似文献
20.
In vivo DNA binding of bacteriophage GA-1 protein p6 总被引:1,自引:0,他引:1
Bacteriophage GA-1 infects Bacillus sp. strain G1R and has a linear double-stranded DNA genome with a terminal protein covalently linked to its 5′ ends. GA-1 protein p6 is very abundant in infected cells and binds DNA with no sequence specificity. We show here that it binds in vivo to the whole viral genome, as detected by cross-linking, chromatin immunoprecipitation, and real-time PCR analyses, and has the characteristics of a histone-like protein. Binding to DNA of GA-1 protein p6 shows little supercoiling dependency, in contrast to the ortholog protein of the evolutionary related Bacillus subtilis phage 29. This feature is a property of the protein rather than the DNA or the cellular background, since 29 protein p6 shows supercoiling-dependent binding to GA-1 DNA in Bacillus sp. strain G1R. GA-1 DNA replication is impaired in the presence of the gyrase inhibitors novobiocin and nalidixic acid, which indicates that, although noncovalently closed, the viral genome is topologically constrained in vivo. GA-1 protein p6 is also able to bind 29 DNA in B. subtilis cells; however, as expected, the binding is less supercoiling dependent than the one observed with the 29 protein p6. In addition, the nucleoprotein complex formed is not functional, since it is not able to transcomplement the DNA replication deficiency of a 29 sus6 mutant. Furthermore, we took advantage of 29 protein p6 binding to GA-1 DNA to find that the viral DNA ejection mechanism seems to take place, as in the case of 29, with a right to left polarity in a two-step, push-pull process. 相似文献