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Phage
Terms modified by Phage Selected AbstractsTHE EVOLUTION OF SPECIFICITY IN EVOLVING AND COEVOLVING ANTAGONISTIC INTERACTIONS BETWEEN A BACTERIA AND ITS PHAGEEVOLUTION, Issue 1 2008Virginie Poullain The evolution of exploitative specificity can be influenced by environmental variability in space and time and the intensity of trade-offs. Coevolution, the process of reciprocal adaptation in two or more species, can produce variability in host exploitation and as such potentially drive patterns in host and parasite specificity. We employed the bacterium Pseudomonas fluorescens SBW25 and its DNA phage ,2 to investigate the role of coevolution in the evolution of phage infectivity range and its relation with phage growth rate. At the phage population level, coevolution led to the evolution of broader infectivity range, but without an associated decrease in phage growth rate relative to the ancestor, whereas phage evolution in the absence of bacterial evolution led to an increased growth rate but no increase in infectivity range. In contrast, both selection regimes led to phage adaptation (in terms of growth rates) to their respective bacterial hosts. At the level of individual phage genotypes, coevolution resulted in within-population diversification in generalist and specialist infectivity range types. This pattern was consistent with a multilocus gene-for-gene interaction, further confirmed by an observed cost of broad infectivity range for individual phage. Moreover, coevolution led to the emergence of bacterial genotype by phage genotype interactions in the reduction of bacterial growth rate by phage. Our study demonstrates that the strong reciprocal selective pressures underlying the process of coevolution lead to the emergence and coexistence of different strategies within populations and to specialization between selective environments. [source] An Action Spectrum of the Riboflavin-photosensitized Inactivation of Lambda Phage,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 2 2005Christopher B. Martin ABSTRACT The Action Spectrum of riboflavin (RB) sensitized inactivation of lambda phage was determined between 266 and 575 nm. Below 304 nm, RB depresses the phage reduction by screening phage from radiation that it would otherwise absorb directly. Between 308 and 525 nm, RB sensitizes the inactivation of phage. Enhanced phage reduction is observed at 320 and 500 nm because of binding of RB to the phage and the shifting of the absorption curve of the phage-bound flavin relative to free flavin in phosphate-buffered saline. Enhanced inactivation at 320 and 500 nm and depressed phage inactivation between 360 and 410 nm is also influenced by the inner filter effect. [source] Phage ,C31 integrase-mediated genomic integration of the common cytokine receptor gamma chain in human T-cell linesTHE JOURNAL OF GENE MEDICINE, Issue 5 2006Yoshinori Ishikawa Abstract Background X-linked severe combined immunodeficiency (SCID-X1, X-SCID) is a life-threatening disease caused by a mutated common cytokine receptor , chain (,c) gene. Although ex vivo gene therapy, i.e., transduction of the ,c gene into autologous CD34+ cells, has been successful for treating SCID-X1, the retrovirus vector-mediated transfer allowed dysregulated integration, causing leukemias. Here, to explore an alternative gene transfer methodology that may offer less risk of insertional mutagenesis, we employed the ,C31 integrase-based integration system using human T-cell lines, including the ,c-deficient ED40515(-). Methods A ,C31 integrase and a neor gene expression plasmid containing the ,C31 attB sequence were co-delivered by electroporation into Jurkat cells. After G418 selection, integration site analyses were performed using linear amplification mediated-polymerase chain reaction (LAM-PCR). ED40515(-) cells were also transfected with a ,c expression plasmid containing attB, and the integration sites were determined. IL-2 stimulation was used to assess the functionality of the transduced ,c in an ED40515(-)-derived clone. Results Following co-introduction of the ,C31 integrase expression plasmid and the plasmid carrying attB, the efficiency of integration into the unmodified human genome was assessed. Several integration sites were characterized, including new integration sites in intergenic regions on chromosomes 13 and 18 that may be preferred in hematopoietic cells. An ED40515(-) line bearing the integrated ,c gene exhibited stable expression of the ,c protein, with normal IL-2 signaling, as assessed by STAT5 activation. Conclusions This study supports the possible future use of this ,C31 integrase-mediated genomic integration strategy as an alternative gene therapy approach for treating SCID-X1. Copyright © 2006 John Wiley & Sons, Ltd. [source] Uniform Amplification of Phage with Different Growth Characteristics in Individual Compartments Consisting of Monodisperse Droplets,ANGEWANDTE CHEMIE, Issue 31 2010Ratmir Derda Dr. Jeder Klon zählt! Beim Phagen-Display gehen Klone, die das Phagenwachstum hemmende Liganden präsentieren, bei der Vervielfältigung verloren. In monodispersen Emulsionen, die mithilfe eines einfachen Mikrofluidiksystems erzeugt wurden, ist die Konkurrenz zwischen langsam (S) und schnell (R) wachsenden Phagen abgemildert, sodass das R/S-Verhältnis beibehalten bleibt. Die konkurrenzfreie Vervielfältigung von Phagen bewahrt Liganden, die im normalen Phagen-Display abhanden kommen. [source] Biomining with bacteriophage: Selectivity of displayed peptides for naturally occurring sphalerite and chalcopyriteBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2009Susan B. Curtis Abstract During mineral processing, concentrates of sulfide minerals of economic interest are formed by froth flotation of fine ore particles. The method works well but recovery and selectivity can be poor for ores with complex mineralogy. There is considerable interest in methods that improve the selectivity of this process while avoiding the high costs of using flotation chemicals. Here we show the first application of phage biotechnology to the processing of economically important minerals in ore slurries. A random heptapeptide library was screened for peptide sequences that bind selectively to the minerals sphalerite (ZnS) and chalcopyrite (CuFeS2). After several rounds of enrichment, cloned phage containing the surface peptide loops KPLLMGS and QPKGPKQ bound specifically to sphalerite. Phage containing the peptide loop TPTTYKV bound to both sphalerite and chalcopyrite. By using an enzyme-linked immunosorbant assay (ELISA), the phage was characterized as strong binders compared to wild-type phage. Specificity of binding was confirmed by immunochemical visualization of phage bound to mineral particles but not to silica (a waste mineral) or pyrite. The current study focused primarily on the isolation of ZnS-specific phage that could be utilized in the separation of sphalerite from silica. At mining sites where sphalerite and chalcopyrite are not found together in natural ores, the separation of sphalerite from silica would be an appropriate enrichment step. At mining sites where sphalerite and chalcopyrite do occur together, more specific phage would be required. This bacteriophage has the potential to be used in a more selective method of mineral separation and to be the basis for advanced methods of mineral processing. Biotechnol. Bioeng. 2009;102: 644,650. © 2008 Wiley Periodicals, Inc. [source] Host range and lytic capability of four bacteriophages against bovine and clinical human isolates of Shiga toxin-producing Escherichia coli O157:H7JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2009Y.D. Niu Abstract Aims:, To evaluate host range and lytic capability of four bacteriophages (rV5, wV7, wV8 and wV11) against Escherichia coli O157:H7 (STEC O157:H7) from cattle and humans. Methods and Results:, Four hundred and twenty-two STEC O157:H7 isolates (297 bovine; 125 human) were obtained in Alberta, Canada. The four phages were serially diluted and incubated for 5 h with overnight cultures of STEC O157:H7 to estimate their multiplicity of infection (MOI). All bovine STEC O157:H7 were subjected to pulsed-field gel electrophoresis (PFGE) and phage typing (PT). Phage wV7 lysed all human and bovine isolates irrespective of PFGE genotype or PT phenotype and exhibited the lowest MOI (0·004,0·006, P < 0·0001) of all phages. Phages rV5 and wV11 exhibited a lower MOI (0·002,0·04, P < 0·0001) than did phage wV8 (25,29) and they had a narrower host range than wV7 or wV8. Phages rV5, wV11 and wV8 lysed 342 (81·0%), 321 (76·1%) and 407 (96·4%), respectively, of the 422 isolates. Susceptibility of bovine STEC O157:H7 to rV5, w11 and wV8 was influenced by PFGE genotype and/or PT phenotype. Conclusions:, Phages exhibited activity against the majority of bovine and human STEC O157:H7 isolates. PFGE genotype and/or PT phenotype of the host-target influenced their vulnerability to phage attack. Susceptibility of bovine STEC O157:H7 to phage may also differ among farms. Both lytic capability and host range should be considered in the selection of therapeutic phage for on-farm control of STEC O157:H7. Significance and Impact of the Study:, The present work indicates that a four-phage cocktail should be equally effective at mitigating STEC O157:H7 isolates both of bovine and of human origin. Given that some STEC O157:H7 exhibited resistance to some but not all phages, a phage cocktail is the logical approach to efficacious on-farm therapy. [source] Phage-mediated transfer of virulence genesJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2001Jon R Saunders Abstract Bacteriophages as accessory genetic elements play a crucial role in the dissemination of genes and the promotion of genetic diversity within bacterial populations. Such horizontal transfer of DNA is critical in the emergence of new pathogenic organisms, through the dissemination of genes encoding virulence factors such as toxins, adhesins and agressins. Phages can transfer genes that are not necessary for bacteriophage persistence and are generally recognised by their ability to convert their host bacteria to new phenotypes. This phenomenon is known as phage conversion. If such converting genes encode for virulence factors, the consequences of phage infection may include increased virulence of the host bacteria, and the conversion of a non-pathogenic strain to a potentially dangerous pathogen. A number of virulence factors in bacteria causing diseases in plants, animals and humans are encoded by converting phages, the vast majority of which are temperate as opposed to lytic in nature. © 2001 Society of Chemical Industry [source] Origin and function of the two major tail proteins of bacteriophage SPP1MOLECULAR MICROBIOLOGY, Issue 3 2008Isabelle Auzat Summary The majority of bacteriophages have a long non-contractile tail (Siphoviridae) that serves as a conduit for viral DNA traffic from the phage capsid to the host cell at the beginning of infection. The 160-nm-long tail tube of Bacillus subtilis bacteriophage SPP1 is shown to be composed of two major tail proteins (MTPs), gp17.1 and gp17.1*, at a ratio of about 3:1. They share a common amino-terminus, but the latter species has ,10 kDa more than gp17.1. A CCC.UAA sequence with overlapping proline codons at the 3, end of gene 17.1 drives a programmed translational frameshift to another open reading frame. The recoding event generates gp17.1*. Phages carrying exclusively gp17.1 or gp17.1* are viable, but tails are structurally distinct. gp17.1 and the carboxyl-terminus of gp17.1* have a distinct evolutionary history correlating with different functions: the polypeptide sequence identical in the two proteins is responsible for assembly of the tail tube while the additional module of gp17.1* shields the structure exterior exposed to the environment. The carboxyl-terminal extension is an elaboration present in some tailed bacteriophages. Different extensions were found to combine in a mosaic fashion with the MTP essential module in a subset of Siphoviridae genomes. [source] Endosialidase NF Appears To Bind PolySia DP5 in a Helical ConformationCHEMBIOCHEM, Issue 12 2006Thomas Haselhorst Dr. Phages infecting the polySia-encapsulated human pathogenE. coli K1 are equipped with capsule-degrading tail spikes known as endosialidases, which are the only identified enzymes that specifically degrade polySia. The X-ray crystallographic structure of endosialidase has been reported but it remains unclear how polySia interacts with the active site. Here we report STD and trNOE NMR experiments that investigate the binding mode of polySia DP5 at a molecular level. [source] Analyzing and monitoring of phage,bacteria interaction using CEELECTROPHORESIS, Issue 20 2009Esra Acar Soykut Abstract The utilization of CE for monitoring bacteria,phage interaction was investigated in this study. Streptococcus thermophilus and Lactobacillus bulgaricus strains and their phages were used as model bacteria and phages for the purpose of validation in this study. CE with heterogeneous polymer polyethylene oxide was utilized for the separation of intact bacteria and investigation of phage,bacteria interaction. An intact phage detection was carried out with CZE by adding SDS in the running buffer. Calibration graphs of bacteria and phages were obtained with R2 values of 0.963 and 0.937, respectively. S. thermophilus strain was infected with its virulent phage B3-X18 for investigation of phage,bacteria interaction. It was observed in capillary electropherogram that the culture was lysed depending on the multiplicity of infection value and it showed to be completely lysed when the multiplicity of infection value was 10. The interaction of S. thermophilus strain with L. bulgaricus phage was also investigated by using a CE and a microbiological method and it was observed that the L. bulgaricus phage attached itself to the cell wall of S. thermophilus strain without damaging the cell. [source] Mutation spectrum in UVB-exposed skin epidermis of Xpa -knockout mice: Frequent recovery of triplet mutationsENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 1 2007Hironobu Ikehata Abstract Knockout mutations in both alleles of the Xpa gene give rise to a complete deficiency in nucleotide excision repair (NER) in mammalian cells. We used transgenic mice harboring the ,-phage-based lacZ mutational reporter gene to study the effect of Xpa null mutation (Xpa,/,) on damage induction, repair, and mutagenesis in mouse skin epidermis after UVB irradiation. UVB induced equal amounts of cyclobutane pyrimidine dimers (CPDs) and pyrimidine(6-4)pyrimidone photoproducts (64PPs) in mouse skin epidermis of Xpa,/, and wild-type mice. Neither photolesion was removed in the Xpa,/, epidermis by 12 hr after irradiation whereas removal of 64PPs was observed in the epidermis of wild-type mice. Irradiation with 200 and 300 J/m2 UVB increased the lacZ mutant frequency in the epidermis of Xpa,/, mice, but the induced mutant frequencies were not significantly different from those previously determined for wild-type mice. One-hundred lacZ mutants isolated from the UVB-exposed epidermis of Xpa,/, mice were analyzed and compared with mutant sequences previously determined for irradiated wild-type mice. The distribution of the mutations along the lacZ transgene and the preferred dipyrimidine context of the UV-specific mutations were similar in mutants from the Xpa,/, and wild-type mice. The spectra of the mutations in the two genotypes were both highly UV-specific and similar in a dominance of C , T transitions at dipyrimidine sites; however, Xpa,/, mice had a higher frequency than wild-type mice of two-base tandem substitutions, including CC , TT mutations, three-base tandem mutations and double base substitutions that were separated by one unchanged base in a three-base sequence (alternating mutations). These tandem/alternating mutations included a remarkably large number of triplet mutations, a recently reported, novel type of UV-specific mutation, characterized by multiple base substitutions or frameshifts within a three-nucleotide sequence containing a dipyrimidine. We conclude that the triplet mutation is a UV-specific mutation that preferably occurs in NER-deficient genetic backgrounds. Environ. Mol. Mutagen., 2007. © 2006 Wiley-Liss, Inc. [source] Genome sequences of two novel phages infecting marine roseobactersENVIRONMENTAL MICROBIOLOGY, Issue 8 2009Yanlin Zhao Summary Two bacteriophages, DSS3,2 and EE36,1, which infect marine roseobacters Silicibacter pomeroyi DSS-3 and Sulfitobacter sp. EE-36, respectively, were isolated from Baltimore Inner Harbor water. These two roseophages resemble bacteriophage N4, a large, short-tailed phage infecting Escherichia coli K12, in terms of their morphology and genomic structure. The full genome sequences of DSS3,2 and EE36,1 reveal that their genome sizes are 74.6 and 73.3 kb, respectively, and they both contain a highly conserved N4-like DNA replication and transcription system. Both roseophages contain a large virion-encapsidated RNA polymerase gene (> 10 kb), which was first discovered in N4. DSS3,2 and EE36,1 also possess several genes (i.e. ribonucleotide reductase and thioredoxin) that are most similar to the genes in roseobacters. Overall, the two roseophages are highly closely related, and share 80,94% nucleotide sequence identity over 85% of their ORFs. This is the first report of N4-like phages infecting marine bacteria and the second report of N4-like phage since the discovery of phage N4 40 years ago. The finding of these two N4-like roseophages will allow us to further explore the specific phage,host interaction and evolution for this unique group of bacteriophages. [source] Key role of selective viral-induced mortality in determining marine bacterial community compositionENVIRONMENTAL MICROBIOLOGY, Issue 2 2007T. Bouvier Summary Viral infection is thought to play an important role in shaping bacterial community composition and diversity in aquatic ecosystems, but the strength of this interaction and the mechanisms underlying this regulation are still not well understood. The consensus is that viruses may impact the dominant bacterial strains, but there is little information as to how viruses may affect the less abundant taxa, which often comprise the bulk of the total bacterial diversity. The potential effect of viruses on the phylogenetic composition of marine bacterioplankton was assessed by incubating marine bacteria collected along a North Pacific coastal-open ocean transect in seawater that was greatly depleted of ambient viruses. The ambient communities were dominated by typical marine groups, including alphaproteobacteria and the Bacteroidetes. Incubation of these communities in virus-depleted ambient water yielded an unexpected and dramatic increase in the relative abundance of bacterial groups that are generally undetectable in the in situ assemblages, such as betaproteobacteria and Actinobacteria. Our results suggest that host susceptibility is not necessarily only proportional to its density but to other characteristics of the host, that rare marine bacterial groups may be more susceptible to viral-induced mortality, and that these rare groups may actually be the winners of competition for resources. These observations are not inconsistent with the ,phage kills the winner' hypothesis but represent an extreme and yet undocumented case of this paradigm, where the potential winners apparently never actually develop beyond a very low abundance threshold in situ. We further suggest that this mode of regulation may influence not just the distribution of single strains but of entire phylogenetic groups. [source] THE EVOLUTION OF SPECIFICITY IN EVOLVING AND COEVOLVING ANTAGONISTIC INTERACTIONS BETWEEN A BACTERIA AND ITS PHAGEEVOLUTION, Issue 1 2008Virginie Poullain The evolution of exploitative specificity can be influenced by environmental variability in space and time and the intensity of trade-offs. Coevolution, the process of reciprocal adaptation in two or more species, can produce variability in host exploitation and as such potentially drive patterns in host and parasite specificity. We employed the bacterium Pseudomonas fluorescens SBW25 and its DNA phage ,2 to investigate the role of coevolution in the evolution of phage infectivity range and its relation with phage growth rate. At the phage population level, coevolution led to the evolution of broader infectivity range, but without an associated decrease in phage growth rate relative to the ancestor, whereas phage evolution in the absence of bacterial evolution led to an increased growth rate but no increase in infectivity range. In contrast, both selection regimes led to phage adaptation (in terms of growth rates) to their respective bacterial hosts. At the level of individual phage genotypes, coevolution resulted in within-population diversification in generalist and specialist infectivity range types. This pattern was consistent with a multilocus gene-for-gene interaction, further confirmed by an observed cost of broad infectivity range for individual phage. Moreover, coevolution led to the emergence of bacterial genotype by phage genotype interactions in the reduction of bacterial growth rate by phage. Our study demonstrates that the strong reciprocal selective pressures underlying the process of coevolution lead to the emergence and coexistence of different strategies within populations and to specialization between selective environments. [source] Physicochemical properties and distinct DNA binding capacity of the repressor of temperate Staphylococcus aureus phage ,11FEBS JOURNAL, Issue 7 2009Tridib Ganguly The repressor protein and cognate operator DNA of any temperate Staphylococcus aureus phage have not been investigated in depth, despite having the potential to enrich the molecular biology of the staphylococcal system. In the present study, using the extremely pure repressor of temperate Staphylococcus aureus phage ,11 (CI), we demonstrate that CI is composed of ,-helix and ,-sheet to a substantial extent at room temperature, possesses two domains, unfolds at temperatures above 39 °C and binds to two sites in the ,11 cI - cro intergenic region with variable affinity. The above CI binding sites harbor two homologous 15 bp inverted repeats (O1 and O2), which are spaced 18 bp apart. Several guanine bases located in and around O1 and O2 demonstrate interaction with CI, indicating that these 15 bp sites are used as operators for repressor binding. CI interacted with O1 and O2 in a cooperative manner and was found to bind to operator DNA as a homodimer. Interestingly, CI did not show appreciable binding to another homologous 15 bp site (O3) that was located in the same primary immunity region as O1 and O2. Taken together, these results suggest that ,11 CI and the ,11 CI,operator complex resemble significantly those of the lambdoid phages at the structural level. The mode of action of ,11 CI, however, may be distinct from that of the repressor proteins of , and related phages. [source] Developing live Shigella vaccines using , Red recombineeringFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 3 2006Ryan T. Ranallo Abstract Live attenuated Shigella vaccines have shown promise in inducing protective immune responses in human clinical trials and as carriers of heterologous antigens from other mucosal pathogens. In the past, construction of Shigella vaccine strains relied on classical allelic exchange systems to genetically engineer the bacterial genome. These systems require extensive in vitro engineering of long homologous sequences to create recombinant replication-defective plasmids or phage. Alternatively, the ,red recombination system from bacteriophage facilitates recombination with as little as 40 bp of homologous DNA. The process, referred to as recombineering, typically uses an inducible ,red operon on a temperature-sensitive plasmid and optimal transformation conditions to integrate linear antibiotic resistance cassettes flanked by homologous sequences into a bacterial genome. Recent advances in recombineering have enabled modification of genomic DNA from bacterial pathogens including Salmonella, Yersinia, enteropathogenic Escherichia coli, or enterohemorrhagic E. coli and Shigella. These advances in recombineering have been used to systematically delete virulence-associated genes from Shigella, creating a number of isogenic strains from multiple Shigella serotypes. These strains have been characterized for attenuation using both in vivo and in vitro assays. Based on this data, prototypic Shigella vaccine strains containing multiple deletions in virulence-associated genes have been generated. [source] Inducible stx2 phages are lysogenized in the enteroaggregative and other phenotypic Escherichia coli O86:HNM isolated from patientsFEMS MICROBIOLOGY LETTERS, Issue 1 2000Sunao Iyoda Abstract We characterized two Shiga toxin-producing Escherichia coli (STEC) O86:HNM isolates from a patient with hemolytic uremic syndrome (HUS) or bloody diarrhea. Both of them did not possess the eaeA gene. However, the isolate from a HUS patient carried genetic markers of enteroaggregative E. coli (EAEC) and showed aggregative adherence pattern to HEp-2 cells. The other isolate from bloody diarrhea, which was negative with EAEC markers, was diffusely adhered to HEp-2 cells. The stx2 gene in both E. coli O86:HNM strains was encoded in each infectious phage, which was partially homologous to that of strain EDL933, a STEC O157:H7. These results will help to explain the genotypic divergences of STEC. [source] DNA bending and looping in the transcriptional control of bacteriophage ,29FEMS MICROBIOLOGY REVIEWS, Issue 5 2010Ana Camacho Abstract Recent studies on the regulation of phage ,29 gene expression reveal new ways to accomplish the processes required for the orderly gene expression in prokaryotic systems. These studies revealed a novel DNA-binding domain in the phage main transcriptional regulator and the nature and dynamics of the multimeric DNA,protein complex responsible for the switch from early to late gene expression. This review describes the features of the regulatory mechanism that leads to the simultaneous activation and repression of transcription, and discusses it in the context of the role of the topological modification of the DNA carried out by two phage-encoded proteins working synergistically with the DNA. [source] Genetically Engineered Phage Fibers and Coatings for Antibacterial ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 2 2010Joan Y. Mao Abstract Multifunctionality can be imparted to protein-based fibers and coatings via either synthetic or biological approaches. Here, potent antimicrobial functionality of genetically engineered, phage-based fibers and fiber coatings, processed at room temperature, is demonstrated. Facile genetic engineering of the M13 virus (bacteriophage) genome leverages the well-known antibacterial properties of silver ions to kill bacteria. Predominant expression of negatively charged glutamic acid (E3) peptides on the pVIII major coat proteins of M13 bacteriophage enables solution-based, electrostatic binding of silver ions and subsequent reduction to metallic silver along the virus length. Antibacterial fibers of micrometer-scale diameters are constructed from such an E3-modified phage via wet-spinning and glutaraldehyde-crosslinking of the E3-modified viruses. Silverization of the free-standing fibers is confirmed via energy dispersive spectroscopy and inductively coupled plasma atomic emission spectroscopy, showing ,0.61,µg cm,1 of silver on E3,Ag fibers. This degree of silverization is threefold greater than that attainable for the unmodified M13,Ag fibers. Conferred bactericidal functionality is determined via live,dead staining and a modified disk-diffusion (Kirby,Bauer) measure of zone of inhibition (ZoI) against Staphylococcus epidermidis and Escherichia coli bacterial strains. Live,dead staining and ZoI distance measurements indicate increased bactericidal activity in the genetically engineered, silverized phage fibers. Coating of Kevlar fibers with silverized E3 phage exhibits antibacterial effects as well, with relatively smaller ZoIs attributable to the lower degree of silver loading attainable in these coatings. Such antimicrobial functionality is amenable to rapid incorporation within fiber-based textiles to reduce risks of infection, biofilm formation, or odor-based detection, with the potential to exploit the additional electronic and thermal conductivity of fully silverized phage fibers and coatings. [source] Genetic transduction in freshwater ecosystemsFRESHWATER BIOLOGY, Issue 6 2008OLADELE A. OGUNSEITAN Summary 1. Lateral genetic exchange is a profound consequence of the co-existence of viruses (bacteriophages) and bacteria in freshwater ecosystems. Transduction is distinct from other mechanisms of genetic exchange because it is driven by potentially lethal agents external to the donor and recipient cells. Therefore, transduction is reputed to be a major driving force behind the diversity in natural populations and communities of bacteria. 2. Both generalized transduction (where every segment of the donor's genome has equal chance of being transferred to a recipient cell) and specialized transduction (where certain donor gene sequences are transferred at higher frequencies than others based on their proximity to the integration site of the transducing bacteriophage genome) have been demonstrated for various freshwater bacteria. However, these genetic exchange events occur at frequencies that vary widely, from 10,2 to 10,10 transductants per recipient, depending on the influence of various physical, chemical and biotic environmental factors on the outcome of phage,host encounters. Methodological constraints limit the interpretation of results from early studies of transduction in freshwaters because those studies introduced exogenous organisms in microcosms and excluded, to different extents, naturally occurring environmental conditions and their variability. 3. To assist the design and extrapolation of empirical observations, mathematical models including application of Group Theory are useful to estimate boundaries of the impact of transduction in generating and maintaining microbial diversity in freshwater. These theoretical excursions generate hypotheses and questions that can only be answered through refinement of current empirical estimates of transduction frequency, polarity of gene mobilization, bacteriophage host ranges, and the influence of gradients in environmental parameters that characterize freshwater ecosystems. [source] Evidence for cyanophages active against bloom-forming freshwater cyanobacteriaFRESHWATER BIOLOGY, Issue 6 2008LI DENG Summary 1. A total of 35 putative cyanophages able to infect non-axenic cultures of bloom-forming freshwater cyanobacteria in the genera Microcystis, Anabaena and Planktothrix were isolated from Lake Zurich (Switzerland) and lakes in the Cotswold Water Park (U.K.). Eleven lytic cyanophage isolates were isolated on Microcystis and 12 each on Anabaena and Planktothrix. Cyanophage isolation protocols varied when using these different cyanobacterial hosts. 2. The collection of putative cyanophage isolates encompassed a variety of morphotypes, including the first filamentous cyanophage from any environment and the second siphocyanophage reported from fresh water. 3. PCR primer sets for gp20, gp23 and MCP genes, which have been previously found to be conserved in other cyanophages, were used in an attempt to determine genetic diversity among the phage isolates. The failure to obtain specific amplification products from most isolates suggests that the cyanophages isolated in this study were different from those previously characterized from both marine and freshwater environments. 4. Some putative cyanophages within the collection of isolates proved to have a very broad host range and were able to infect Anabaena, Microcystis and Planktothrix. The ability to infect a wide range of host taxa extends the potential reproductive period for lytic propagation, and also has implications for the transfer of genetic information between deeply separated cyanobacterial lineages. [source] Gene products encoded in the ninR region of phage , participate in Red-mediated recombinationGENES TO CELLS, Issue 4 2002Trudee A. Tarkowski Background:, The ninR region of phage , contains two recombination genes, orf (ninB) and rap (ninG), that were previously shown to have roles when the RecF and RecBCD recombination pathways of E. coli, respectively, operate on phage ,. Results:, When , DNA replication is blocked, recombination is focused at the termini of the virion chromosome. Deletion of the ninR region of , decreases the sharpness of the focusing without diminishing the overall rate of recombination. The phenotype is accounted for in large part by the deletion of rap and of orf. Mutation of the recJ gene of the host partially suppresses the Rap, phenotype. Conclusion: ninR functions Orf and Rap participate in Red recombination, the primary pathway operating when wild-type , grows lytically in rec+ cells. The ability of recJ mutation to suppress the Rap, phenotype indicates that RecJ exonuclease can participate in Red-mediated recombination, at least in the absence of Rap function. A model is presented for Red-mediated RecA-dependent recombination that includes these newly identified participants. [source] Liquid Crystal Emulsions as the Basis of Biological Sensors for the Optical Detection of Bacteria and VirusesADVANCED FUNCTIONAL MATERIALS, Issue 14 2009Sri Sivakumar Abstract A versatile sensing method based on monodisperse liquid crystal (LC) emulsion droplets detects and distinguishes between different types of bacteria (Gram +ve and ,ve) and viruses (enveloped and non-enveloped). LCs of 4-cyano-4'-pentylbiphenyl transition from a bipolar to radial configuration when in contact with Gram ,ve bacteria (E. coli) and lipid-enveloped viruses (A/NWS/Tokyo/67). This transition is consistent with the transfer of lipid from the organisms to the interfaces of the micrometer-sized LC droplets. In contrast, a transition to the radial configuration is not observed in the presence of Gram +ve bacteria (Bacillus subtilis and Micrococcus luteus) and non-enveloped viruses (M13 helper phage). The LC droplets can detect small numbers of E. coli bacteria (1,5) and low concentrations (104,pfu mL,1) of A/NWS/Tokyo/67 virus. Monodisperse LC emulsions incubated with phosholipid liposomes (similar to the E. coli cell wall lipid) reveal that the orientational change is triggered at an area per lipid molecule of ,46,Å2 on an LC droplet (,1.6,×,108 lipid molecules per droplet). This approach represents a novel means to sense and differentiate between types of bacteria and viruses based on their cell-wall/envelope structure, paving the way for the development of a new class of LC microdroplet-based biological sensors. [source] Phage display of human antibodies from a patient suffering from coeliac disease and selection of isotype-specific scFv against gliadinIMMUNOLOGY, Issue 2 2003Claudio Rhyner Summary Coeliac disease (CD), a gastrointestinal illness characterized by intestinal malabsorption, results from gluten intolerance accompanied with immunological responses towards gliadin, an ethanol-soluble protein fraction of wheat and other cereals. The role of gliadin in eliciting immune responses in CD is still partly unclear; however, the occurrence of anti-gliadin in the sera of patients suffering from CD correlates well with clinical symptoms. In this work we report the construction of isotype-specific, phage-displayed scFv libraries from peripheral blood lymphocytes of a patient with CD and from a healthy control individual. VH and VL chains were amplified by reverse transcription,polymerase chain reaction (RT,PCR) using a set of oligonucleotides recognizing all human variable gene families. The three scFv libraries (IgA, IgG and IgM) were selectively enriched for gliadin-binding phage. After four rounds of affinity selection, polyclonal enrichment of gliadin-binding phage was observed in all libraries from the CD patient but in none from the healthy donor. Phagemid particles generated from single clones were demonstrated to be gliadin-specific, as shown by strongly positive enzyme-linked immunosorbent assay (ELISA) and BiaCore signals. The VH and VL chains from samples of these monoclonal isotype-specific phage were sequenced to identify the most common variable regions used by the immune system to elicit antibody responses against gliadin. [source] Screening for natural defence mechanisms of Lactococcus lactis strains isolated from traditional starter culturesINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 7 2007Andreja Mikli Summary Three different bacterial defence mechanisms were identified in the seventeen Lactococcus lactis isolates from starter cultures in three Slovenian dairy plants. Isolates MB18, KR7, PT4, PT13 and PT19 inhibited phage adsorption by means of exopolysaccharides production. The most extensive polysaccharides production was detected in PT19 isolate, which was susceptible only to phage ,PT19. Eight isolates exhibited nuclease activity, and seven of them were susceptible up to four phages out of thirteen from our collection. Eight isolates possessed the abiB gene, fourteen isolates abiH, two isolates abiJ and one isolate abiQ. Isolates PT27 and PT28 possessed AbiB, AbiH and AbiJ mechanisms as well as inhibition of phage adsorption. Isolate MB18, which was susceptible to one phage only, possessed the abiQ gene, nuclease activity and ability to prevent adsorption of most phages. Isolates PT67 and PT70, possessing only AbiH mechanism, were susceptible to only two phages. [source] Quantitative PCR assays to survey the bovine adenovirus levels in environmental samplesJOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2010K. Wong Abstract Aims:, Previous studies suggested bovine adenoviruses (BAdVs) could be used as cattle faecal indicators. The main aim of this study was to survey the levels of BAdV in environmental samples using quantitative polymerase chain reaction (qPCR). Methods and Results:, Two qPCR assays were developed to identify and quantify BAdVs in environmental samples. BAdVs were detected in all dairy manure, and in most cases, the sample concentrations were around 103,104 copies ml,1. Farm tile drainage samples were also detected, but the concentrations were about 1,3 log10 lower than the BAdV concentrations in the manure samples. The genome equivalent copy (GEC) levels of BAdV and the phage forming unit (PFU) levels of somatic phage in manure samples were comparable. Four of twenty individual cattle faeces were positive with concentrations similar to that found in the manure samples. Sequencing results confirmed the presence of BAdV in the environmental samples, and phylogenetic analysis indicated that BAdV 2 and 4 were the most prevalent serotypes in all the manure samples tested. The qPCR assays developed in this study showed higher sensitivity in detecting BAdV 1 and 2 than the previous published nested assay. Conclusion:, The high levels of BAdV in the environmental samples may suggest it could be used for bovine faecal indicator. The significant levels of BAdV in the drainage samples may indicate the potential of surface water pollution by the manure applied to farm fields. Significance and Impact of the Study:, This is the first study that reports the quantitative level of BAdV in environmental samples. These results could be useful when it comes to determining whether BAdV could be utilized as a bovine faecal indicator. [source] Host range and lytic capability of four bacteriophages against bovine and clinical human isolates of Shiga toxin-producing Escherichia coli O157:H7JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2009Y.D. Niu Abstract Aims:, To evaluate host range and lytic capability of four bacteriophages (rV5, wV7, wV8 and wV11) against Escherichia coli O157:H7 (STEC O157:H7) from cattle and humans. Methods and Results:, Four hundred and twenty-two STEC O157:H7 isolates (297 bovine; 125 human) were obtained in Alberta, Canada. The four phages were serially diluted and incubated for 5 h with overnight cultures of STEC O157:H7 to estimate their multiplicity of infection (MOI). All bovine STEC O157:H7 were subjected to pulsed-field gel electrophoresis (PFGE) and phage typing (PT). Phage wV7 lysed all human and bovine isolates irrespective of PFGE genotype or PT phenotype and exhibited the lowest MOI (0·004,0·006, P < 0·0001) of all phages. Phages rV5 and wV11 exhibited a lower MOI (0·002,0·04, P < 0·0001) than did phage wV8 (25,29) and they had a narrower host range than wV7 or wV8. Phages rV5, wV11 and wV8 lysed 342 (81·0%), 321 (76·1%) and 407 (96·4%), respectively, of the 422 isolates. Susceptibility of bovine STEC O157:H7 to rV5, w11 and wV8 was influenced by PFGE genotype and/or PT phenotype. Conclusions:, Phages exhibited activity against the majority of bovine and human STEC O157:H7 isolates. PFGE genotype and/or PT phenotype of the host-target influenced their vulnerability to phage attack. Susceptibility of bovine STEC O157:H7 to phage may also differ among farms. Both lytic capability and host range should be considered in the selection of therapeutic phage for on-farm control of STEC O157:H7. Significance and Impact of the Study:, The present work indicates that a four-phage cocktail should be equally effective at mitigating STEC O157:H7 isolates both of bovine and of human origin. Given that some STEC O157:H7 exhibited resistance to some but not all phages, a phage cocktail is the logical approach to efficacious on-farm therapy. [source] The newly isolated lytic bacteriophages st104a and st104b are highly virulent against Salmonella entericaJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2006G. O'Flynn Abstract Aims:, To screen Irish faecal samples from a variety of sources with a view to isolating novel anti- Salmonella phages and to subsequently evaluate their lytic capability. Methods and Results:, Two novel anti- Salmonella phages st104a and st104b were isolated from a screening programme based on their lytic capability. The phages produced significantly larger plaques (2 mm) on the chosen indicator Salmonella enterica strain, DPC6046, when compared with the well-known control phage, Felix 01 (0·5 mm). Both phages st104a and st104b were found to have a broad host range within the Salm. enterica species. During in vitro trials, both phages (st104a and st104b) reduced Salm. enterica numbers more than 99% within 1 h. In vivo studies, involving the addition of the phage to porcine gastric juice (pH 2·5) demonstrated that phage st104a and phage Felix 01 were capable of surviving (10 and 30% survival respectively) the acidic conditions, unlike st104b, which was undetectable after 2 h exposure. Conclusions:, Two novel lytic anti- Salmonella phages were isolated and characterized. Significance and Impact of the Study:, With the exception of phage Felix 01, there has been relatively little phage therapy work performed using lytic Salmonella phage. In this study, the lytic phages st104a and st104b were isolated as a result of a faecal screening programme. Subsequently, phage st104a was found to have potential for biocontrol of Salm. enterica numbers if administered orally to pigs given their survival in porcine gastric juice, whereas, phage st104b may have potential in reducing cell numbers if applied by alternative approaches. [source] Coinfection with Campylobacter species: an epidemiological problem?JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2001J.F. Richardson Aims: To determine the frequency of coinfection with multiple strains in sporadic cases of human Campylobacter infection. Method and Results: During 1999 10 single colonies of Campylobacter were cultured from each of 53 positive faecal samples. Five isolates were taken from nonselective agar after passive filtration of faecal suspensions and five isolates were taken from selective agar plates. All isolates were sero- and phage typed and their antibiotic resistance determined. Pulsed-field gel electrophoresis and flagellin gene typing were performed on selected isolates. One patient was infected with Camp. coli, the remainder with strains of Camp. jejuni. The majority of patients was infected with a single strain of Campylobacter, but from each of four samples, 7·5%, two strains of Camp. jejuni, confirmed by molecular typing, were identified. Conclusions: Coinfection occurs in sporadic cases of campylobacteriosis. Significance and Impact of the Study: This study has implications in outbreak investigation when distinct strains have been isolated from epidemiologically related patients and/or the suspected source or vehicle. [source] Activity of Serratia plymuthica IC1270 gene chiA promoter region in Escherichia coli mutants deficient in global regulators of transcriptionJOURNAL OF BASIC MICROBIOLOGY, Issue 6 2005I. A. Khmel To study the regulation of expression of the Serratia plymuthica gene chiA encoding a 58-kDa endochitinase, its 586-bp-long upstream regulatory region was cloned, sequenced and fused to a promoterless lac operon in phage ,RS45 to obtain a single-copy transcriptional fusion (PF1chiA - lac ) in lysogens of Escherichia coli wild-type strains or their mutants deficient in various global regulators of transcription. The level of PF1chiA - lac expression increased about 20- and 90-fold, respectively, in E. coli K12 ,hns and double ,hns stpA mutants deficient in H-NS, and in both H-NS and StpA DNA-binding histone-like proteins, as compared to levels in the wild-type strain. In a ,lrp mutant deficient in the leucine-responsive transcriptional regulator Lrp, the level of PF1chiA - lac expression increased only up to threefold, whereas even smaller differences relative to the wild-type strain were observed in rpoS and ,crp mutants deficient in the ,S subunit of RNA polymerase and catabolite-repression protein (CRP), respectively. Deletion of the inverted-repeat sequences and curved DNA regions located in the upstream region of chiA essentially did not influence strain IC1270's chiA promoter activity in E. coli . (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||||||||||||||