The Experts below are selected from a list of 102 Experts worldwide ranked by ideXlab platform
Maite Muniesa - One of the best experts on this subject based on the ideXlab platform.
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Antibiotic Resistance Genes in the Bacteriophage DNA Fraction of Human Fecal Samples
Antimicrobial agents and chemotherapy, 2013Co-Authors: Pablo Quirós, Marta Colomer-lluch, Juan Jofre, Alexandre Martínez-castillo, Elisenda Miró, Marc Argente, Ferran Navarro, Maite MuniesaAbstract:A group of antibiotic resistance genes (ARGs) (blaTEM, blaCTX-M-1, mecA, armA, qnrA, and qnrS) were analyzed by real-time quantitative PCR (qPCR) in Bacteriophage DNA isolated from feces from 80 healthy humans. Seventy-seven percent of the samples were positive in phage DNA for one or more ARGs. blaTEM, qnrA, and, blaCTX-M-1 were the most abundant, and armA, qnrS, and mecA were less prevalent. Free Bacteriophages carrying ARGs may contribute to the mobilization of ARGs in intra- and extraintestinal environments.
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Antibiotic resistance genes in the Bacteriophage DNA fraction of environmental samples
PLoS ONE, 2011Co-Authors: Marta Colomer-lluch, Juan Jofre, Maite MuniesaAbstract:Antibiotic resistance is an increasing global problem resulting from the pressure of antibiotic usage, greater mobility of the population, and industrialization. Many antibiotic resistance genes are believed to have originated in microorganisms in the environment, and to have been transferred to other bacteria through mobile genetic elements. Among others, β-lactam antibiotics show clinical efficacy and low toxicity, and they are thus widely used as antimicrobials. Resistance to β-lactam antibiotics is conferred by β-lactamase genes and penicillin-binding proteins, which are chromosomal- or plasmid-encoded, although there is little information available on the contribution of other mobile genetic elements, such as phages. This study is focused on three genes that confer resistance to β-lactam antibiotics, namely two β-lactamase genes (blaTEM and blaCTX-M9) and one encoding a penicillin-binding protein (mecA) in Bacteriophage DNA isolated from environmental water samples. The three genes were quantified in the DNA isolated from Bacteriophages collected from 30 urban sewage and river water samples, using quantitative PCR amplification. All three genes were detected in the DNA of phages from all the samples tested, in some cases reaching 104 gene copies (GC) of blaTEM or 102 GC of blaCTX-M and mecA. These values are consistent with the amount of fecal pollution in the sample, except for mecA, which showed a higher number of copies in river water samples than in urban sewage. The bla genes from phage DNA were transferred by electroporation to sensitive host bacteria, which became resistant to ampicillin. blaTEM and blaCTX were detected in the DNA of the resistant clones after transfection. This study indicates that phages are reservoirs of resistance genes in the environment.
Jerry A. Harpst - One of the best experts on this subject based on the ideXlab platform.
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Effects of Na+ on the persistence length and excluded volume of T7 Bacteriophage DNA.
Biopolymers, 1991Co-Authors: E. S. Sobel, Jerry A. HarpstAbstract:Total intensity, Rayleigh light scattering has been used to measure the rms radius, second virial coefficient, persistence length, and excluded volume of homogeneous T7 Bacteriophage DNA as a function of Na+ concentration (0.005 to 3.0 M). All parameters decrease sharply as [Na+] increases, and tend to level off at high Na+. The variation of persistence length with [Na+] is consistent with predictions from counterion condensation theory.
Marta Colomer-lluch - One of the best experts on this subject based on the ideXlab platform.
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Antibiotic Resistance Genes in the Bacteriophage DNA Fraction of Human Fecal Samples
Antimicrobial agents and chemotherapy, 2013Co-Authors: Pablo Quirós, Marta Colomer-lluch, Juan Jofre, Alexandre Martínez-castillo, Elisenda Miró, Marc Argente, Ferran Navarro, Maite MuniesaAbstract:A group of antibiotic resistance genes (ARGs) (blaTEM, blaCTX-M-1, mecA, armA, qnrA, and qnrS) were analyzed by real-time quantitative PCR (qPCR) in Bacteriophage DNA isolated from feces from 80 healthy humans. Seventy-seven percent of the samples were positive in phage DNA for one or more ARGs. blaTEM, qnrA, and, blaCTX-M-1 were the most abundant, and armA, qnrS, and mecA were less prevalent. Free Bacteriophages carrying ARGs may contribute to the mobilization of ARGs in intra- and extraintestinal environments.
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Antibiotic resistance genes in the Bacteriophage DNA fraction of environmental samples
PLoS ONE, 2011Co-Authors: Marta Colomer-lluch, Juan Jofre, Maite MuniesaAbstract:Antibiotic resistance is an increasing global problem resulting from the pressure of antibiotic usage, greater mobility of the population, and industrialization. Many antibiotic resistance genes are believed to have originated in microorganisms in the environment, and to have been transferred to other bacteria through mobile genetic elements. Among others, β-lactam antibiotics show clinical efficacy and low toxicity, and they are thus widely used as antimicrobials. Resistance to β-lactam antibiotics is conferred by β-lactamase genes and penicillin-binding proteins, which are chromosomal- or plasmid-encoded, although there is little information available on the contribution of other mobile genetic elements, such as phages. This study is focused on three genes that confer resistance to β-lactam antibiotics, namely two β-lactamase genes (blaTEM and blaCTX-M9) and one encoding a penicillin-binding protein (mecA) in Bacteriophage DNA isolated from environmental water samples. The three genes were quantified in the DNA isolated from Bacteriophages collected from 30 urban sewage and river water samples, using quantitative PCR amplification. All three genes were detected in the DNA of phages from all the samples tested, in some cases reaching 104 gene copies (GC) of blaTEM or 102 GC of blaCTX-M and mecA. These values are consistent with the amount of fecal pollution in the sample, except for mecA, which showed a higher number of copies in river water samples than in urban sewage. The bla genes from phage DNA were transferred by electroporation to sensitive host bacteria, which became resistant to ampicillin. blaTEM and blaCTX were detected in the DNA of the resistant clones after transfection. This study indicates that phages are reservoirs of resistance genes in the environment.
Harold G. Craighead - One of the best experts on this subject based on the ideXlab platform.
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Individually Resolved DNA Molecules Stretched and Embedded in Electrospun Polymer Nanofibers
Nano letters, 2006Co-Authors: Leon M. Bellan, Joshua D. Cross, Elizabeth A. Strychalski, Jose M. Moran-mirabal, Harold G. CraigheadAbstract:We have used the flow characteristics of an electrospinning jet to elongate and fix DNA molecules. We embedded and observed fluorescently labeled λ Bacteriophage DNA molecules in polyethylene oxide nanofibers. The embedded DNA molecules were imaged using fluorescence microscopy and found to be stretched to lengths approaching the full dyed contour length.
Philip Serwer - One of the best experts on this subject based on the ideXlab platform.
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A Hypothesis for Bacteriophage DNA Packaging Motors
Viruses, 2010Co-Authors: Philip SerwerAbstract:The hypothesis is presented that Bacteriophage DNA packaging motors have a cycle comprised of bind/release thermal ratcheting with release-associated DNA pushing via ATP-dependent protein folding. The proposed protein folding occurs in crystallographically observed peptide segments that project into an axial channel of a protein 12-mer (connector) that serves, together with a coaxial ATPase multimer, as the entry portal. The proposed cycle begins when reverse thermal motion causes the connector’s peptide segments to signal the ATPase multimer to bind both ATP and the DNA molecule, thereby producing a dwell phase recently demonstrated by single-molecule procedures. The connector-associated peptide segments activate by transfer of energy from ATP during the dwell. The proposed function of connector/ATPase symmetry mismatches is to reduce thermal noise-induced signaling errors. After a dwell, ATP is cleaved and the DNA molecule released. The activated peptide segments push the released DNA molecule, thereby producing a burst phase recently shown to consist of four mini-bursts. The constraint of four mini-bursts is met by proposing that each mini-burst occurs via pushing by three of the 12 subunits of the connector. If all four mini-bursts occur, the cycle repeats. If the mini-bursts are not completed, a second cycle is superimposed on the first cycle. The existence of the second cycle is based on data recently obtained with Bacteriophage T3. When both cycles stall, energy is diverted to expose the DNA molecule to maturation cleavage.
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Models of Bacteriophage DNA packaging motors.
Journal of structural biology, 2003Co-Authors: Philip SerwerAbstract:An ATP-dependent motor drives a DNA genome into a Bacteriophage capsid during morphogenesis of double-stranded DNA Bacteriophages both in vivo and in vitro. The DNA molecule enters the capsid through a channel in the center of a symmetric protein ring called a connector. Mechanisms in two classes have been proposed for this motor: (1) An ATP-driven rotating connector pulls a DNA molecule via serial power strokes. (2) The connector rectifies DNA motion that is either thermal, biased thermal, or oscillating electrical field-induced (motor-ratchet hypothesis). Mechanisms in the first class have previously been proposed to explain the detailed structure of DNA packaging motors. The present study demonstrates that the motor-ratchet hypothesis also explains the current data, including data in the following categories: biochemical genetics, energetics, structure, and packaging dynamics.
