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Wanida Phetsang, Ruby Pelingon, Mark S Butler, Sanjaya Kc, Miranda E Pitt, Geraldine Kaeslin, Matthew A Cooper, Mark A T Blaskovich
Reduced susceptibility to antimicrobials in Gram-negative bacteria may result from multiple resistance mechanisms, including increased efflux pump activity or reduced porin protein expression. Up-regulation of the efflux pump system is closely associated with multidrug resistance (MDR). To help investigate the role of efflux pumps on compound accumulation, a fluorescence-based assay was developed using fluorescent derivatives of trimethoprim (TMP), a broad-spectrum synthetic antibiotic that inhibits an intracellular target, dihydrofolate reductase (DHFR)...
October 14, 2016: ACS Infectious Diseases
P Benjamin Stranges, Mirkó Palla, Sergey Kalachikov, Jeff Nivala, Michael Dorwart, Andrew Trans, Shiv Kumar, Mintu Porel, Minchen Chien, Chuanjuan Tao, Irina Morozova, Zengmin Li, Shundi Shi, Aman Aberra, Cleoma Arnold, Alexander Yang, Anne Aguirre, Eric T Harada, Daniel Korenblum, James Pollard, Ashwini Bhat, Dmitriy Gremyachinskiy, Arek Bibillo, Roger Chen, Randy Davis, James J Russo, Carl W Fuller, Stefan Roever, Jingyue Ju, George M Church
Scalable, high-throughput DNA sequencing is a prerequisite for precision medicine and biomedical research. Recently, we presented a nanopore-based sequencing-by-synthesis (Nanopore-SBS) approach, which used a set of nucleotides with polymer tags that allow discrimination of the nucleotides in a biological nanopore. Here, we designed and covalently coupled a DNA polymerase to an α-hemolysin (αHL) heptamer using the SpyCatcher/SpyTag conjugation approach. These porin-polymerase conjugates were inserted into lipid bilayers on a complementary metal oxide semiconductor (CMOS)-based electrode array for high-throughput electrical recording of DNA synthesis...
October 11, 2016: Proceedings of the National Academy of Sciences of the United States of America
Christina M Beck, Julia L E Willett, David A Cunningham, Jeff J Kim, David A Low, Christopher S Hayes
Many Gram-negative bacterial pathogens express contact-dependent growth inhibition (CDI) systems that promote cell-cell interaction. CDI+ bacteria express surface CdiA effector proteins, which transfer their C-terminal toxin domains into susceptible target cells upon binding to specific receptors. CDI+ cells also produce immunity proteins that neutralize the toxin domains delivered from neighboring siblings. Here, we show that CdiAEC536 from uropathogenic Escherichia coli 536 (EC536) uses OmpC and OmpF as receptors to recognize target bacteria...
October 2016: PLoS Pathogens
Yasemin Cag, Hulya Caskurlu, Yanyan Fan, Bin Cao, Haluk Vahaboglu
By definition, the terms sepsis and septic shock refer to a potentially fatal infectious state in which the early administration of an effective antibiotic is the most significant determinant of the outcome. Because of the global spread of resistant bacteria, the efficacy of antibiotics has been severely compromised. S. pneumonia, Escherichia coli (E. coli), Klebsiella, Acinetobacter, and Pseudomonas are the predominant pathogens of sepsis and septic shock. It is common for E. coli, Klebsiella, Acinetobacter and Pseudomonas to be resistant to multiple drugs...
September 2016: Annals of Translational Medicine
Inamullah Hakeem Said, Rohan Lakshmidas Shah, Matthias S Ullrich, Nikolai Kuhnert
A liquid chromatography-mass spectrometry-based method for the quantification of intracellular concentrations of dietary phenolics in bacteria was developed. Using this assay, the time-dependent uptake of quercetin and two of its glycosides into gut microbiota model organisms (Escherichia coli and Bifidobacterium bifidum) under aerobic and anaerobic conditions was studied. For the first time, quantitative data on the uptake of dietary phenols were obtained indicating a time-dependent differential uptake of the dietary compounds...
September 14, 2016: Food & Function
Verena Ducret, Manuel R Gonzalez, Tiziana Scrignari, Karl Perron
The metal-specific CzcRS two-component system in Pseudomonas aeruginosa is involved in the repression of the OprD porin, causing in turn carbapenem antibiotic resistance in the presence of high zinc concentration. It has also been shown that CzcR is able to directly regulate the expression of multiple genes including virulence factors. CzcR is therefore an important regulator connecting (i) metal response, (ii) pathogenicity and (iii) antibiotic resistance in P. aeruginosa. Recent data have suggested that other regulators could negatively control oprD expression in the presence of zinc...
October 3, 2016: Genes
Luana G M Ferrara, Gregor D Wallat, Lucile Moynié, Naresh N Dhanasekar, Soumeya Aliouane, Silvia Acosta-Gutiérrez, Jean-Marie Pagès, Jean-Michel Bolla, Mathias Winterhalter, Matteo Ceccarelli, James H Naismith
The Gram-negative organism Campylobacter jejuni is the major cause of food poisoning. Unlike Escherichia coli, which has two major porins, OmpC and OmpF, C. jejuni has one, termed major outer membrane protein (MOMP) through which nutrients and antibiotics transit. We report the 2.1-Å crystal structure of C. jejuni MOMP expressed in E. coli and a lower resolution but otherwise identical structure purified directly from C. jejuni. The 2.1-Å resolution structure of recombinant MOMP showed that although the protein has timeric arrangement similar to OmpC, it is an 18-stranded, not 16-stranded, β-barrel...
September 30, 2016: Journal of Molecular Biology
Emma V Ainsworth, Colin Wj Lockwood, Gaye F White, Ee Taek Hwang, Tsubasa Sakai, Manuela A Gross, David J Richardson, Thomas A Clarke, Lars Jc Jeuken, Erwin Reisner, Julea N Butt
The transfer of photoenergized electrons from extracellular photosensitizers across a bacterial cell envelope to drive intracellular chemical transformations represents an attractive way to harness Nature's catalytic machinery for solar to chemicals conversion. In Shewanella oneidensis MR-1 (MR-1) trans-outermembrane electron transfer is performed by the extracellular cytochromes MtrC and OmcA acting together with the outermembrane spanning porin:cytochrome complex (MtrAB). Here we demonstrate photoreduction of solutions of MtrC, OmcA and the MtrCAB complex by soluble photosensitizers, namely, eosin Y, fluorescein, proflavine, flavin adenine dinucleotide and two compounds secreted by MR-1, riboflavin and flavin mononucleotide...
September 29, 2016: Chembiochem: a European Journal of Chemical Biology
Samuel I Miller
The Gram-negative outer membrane is an important barrier that provides protection against toxic compounds, which include antibiotics and host innate immune molecules such as cationic antimicrobial peptides. Recently, significant research progress has been made in understanding the biogenesis, regulation, and functioning of the outer membrane, including a recent paper from the laboratory of Dr. Brett Finlay at the University of British Columbia (J. van der Heijden et al., mBio 7:e01238-16, 2016, http://dx.doi...
September 27, 2016: MBio
Baharak Babouee Flury, Matthew J Ellington, Katie L Hopkins, Jane F Turton, Michel Doumith, Neil Woodford
Mechanisms leading to carbapenem and cephalosporin resistance were sought in Enterobacter aerogenes isolates that were highly resistant to carbapenems but had no known carbapenemase. Results were compared with recent work examining carbapenem-resistant Enterobacter cloacae. Eighteen carbapenem-resistant E. aerogenes were screened for known β-lactamase and carbapenemase genes, and novel carbapenemases were sought in whole-genome sequencing (WGS) data of the three most resistant isolates. For all isolates, ampC, ampR, ampD and the porin genes omp35 and omp36 were investigated by Sanger sequencing or from available WGS data...
September 12, 2016: International Journal of Antimicrobial Agents
Chaman Ranjit, Kenneth M Noll
Thermotoga maritima cells are distinguished by a sheath-like structure called the toga that loosely encloses single or multiple cells. During growth, and particularly at late phases of population growth, the toga distends from the poles of many cells. Little is known about this phenomenon so this study presents basic information about this process. We first provide quantitative data demonstrating that cells showing toga distensions increase in number during growth and that the phenomenon is not due to acidification of their growth medium...
October 2016: FEMS Microbiology Letters
Etsuko Sugawara, Seiji Kojima, Hiroshi Nikaido
: Klebsiella pneumoniae, one of the most important nosocomial pathogens, is becoming a major problem in health care because of its resistance to multiple antibiotics including cephalosporins of the latest generation and more recently even carbapenems. This is largely due to the spread of plasmid-coded extended spectrum β-lactamases. However, antimicrobial agents must first penetrate through the outer membrane barrier in order to reach their targets, and hydrophilic and charged β-lactams presumably diffuse through the porin channels...
September 19, 2016: Journal of Bacteriology
Tackmin Kwon
The efficiency of Agrobacterium-mediated transformation in plants depends on the virulence of Agrobacterium strains, the plant tissue culture conditions, and the susceptibility of host plants. Understanding the molecular interactions between Agrobacterium and host plant cells is crucial when manipulating the susceptibility of recalcitrant crop plants and protecting orchard trees from crown gall disease. It was discovered that Arabidopsis voltage-dependent anion channel 1 (atvdac1) mutant has drastic effects on Agrobacterium-mediated tumorigenesis and growth developmental phenotypes, and that these effects are dependent on a Ws-0 genetic background...
September 2016: Molecules and Cells
Jaewoon Jung, Akira Naurse, Chigusa Kobayashi, Yuji Sugita
The graphics processing unit (GPU) has become a popular computational platform for molecular dynamics (MD) simulations of biomolecules. A significant speedup in the simulations of small- or medium-size systems using only a few computer nodes with a single or multiple GPUs has been reported. Because of GPU memory limitation and slow communication between GPUs on different computer nodes, it is not straightforward to accelerate MD simulations of large biological systems that contain a few million or more atoms on massively parallel supercomputers with GPUs...
October 11, 2016: Journal of Chemical Theory and Computation
Katherine A Rhodes, Herbert P Schweizer
The genus Burkholderia comprises metabolically diverse and adaptable Gram-negative bacteria, which thrive in often adversarial environments. A few members of the genus are prominent opportunistic pathogens. These include Burkholderia mallei and Burkholderia pseudomallei of the B. pseudomallei complex, which cause glanders and melioidosis, respectively. Burkholderia cenocepacia, Burkholderia multivorans, and Burkholderia vietnamiensis belong to the Burkholderia cepacia complex and affect mostly cystic fibrosis patients...
September 2016: Drug Resistance Updates: Reviews and Commentaries in Antimicrobial and Anticancer Chemotherapy
Joachim Lauterwasser, Franziska Todt, Ralf M Zerbes, Thanh Ngoc Nguyen, William Craigen, Michael Lazarou, Martin van der Laan, Frank Edlich
The pro-apoptotic Bcl-2 protein Bax can permeabilize the outer mitochondrial membrane and therefore commit human cells to apoptosis. Bax is regulated by constant translocation to the mitochondria and retrotranslocation back into the cytosol. Bax retrotranslocation depends on pro-survival Bcl-2 proteins and stabilizes inactive Bax. Here we show that Bax retrotranslocation shuttles membrane-associated and membrane-integral Bax from isolated mitochondria. We further discover the mitochondrial porin voltage-dependent anion channel 2 (VDAC2) as essential component and platform for Bax retrotranslocation...
2016: Scientific Reports
S Ghafourian
The main mechanism of quinolone resistance in K pneumoniae caused via mutation on porin-related proteins and efflux pumps. The current study aimed investigates the prevalence of ciprofloxacin resistant K pneumoniae in burn patients and understanding the role of AcrAB multidrug efflux system on minimal inhibitory concentration of ciprofloxacin. For this reason, 52 K pneumoniae collected from burn patients and evaluated for mechanism of ciprofloxacin resistance. The results demonstrated 40 K pneumoniae were ciprofloxacin resistant K pneumonia and 35 showed the mutation on gyrA...
March 10, 2016: West Indian Medical Journal
Luisa Samaniego-Barrón, Sarahí Luna-Castro, Carolina Piña-Vázquez, Francisco Suárez-Güemes, Mireya de la Garza
Mannheimia haemolytica is a Gram negative bacterium that is part of the bovine respiratory disease, which causes important economic losses in the livestock industry. In the present work, the interaction between M. haemolytica A1 and bovine lactoferrin (BLf) was studied. This iron-chelating glycoprotein is part of the mammalian innate-immune system and is present in milk and mucosal secretions; Lf is also contained in neutrophils secondary granules, which release this glycoprotein at infection sites. It was evidenced that M...
2016: Veterinary Research
Mohamed H Al-Agamy, Katy Jeannot, Taghrid S El-Mahdy, Hassan A Samaha, Atef M Shibl, Patrick Plésiat, Patrice Courvalin
Background. This study described various molecular and epidemiological characters determining antibiotic resistance patterns in Pseudomonas aeruginosa isolates. Methods. A total of 34 carbapenem-resistant P. aeruginosa clinical isolates were isolated from samples collected at a tertiary hospital in Riyadh, Saudi Arabia, from January to December 2011. Susceptibility testing, serotyping, molecular characterization of carbapenem resistance, and pulsed-field gel electrophoresis (PFGE) were performed. Results. All isolates were resistant to ceftazidime, and more than half were highly resistant (minimum inhibitory concentration (MIC) > 256 mg/L)...
2016: Canadian Journal of Infectious Diseases & Medical Microbiology
Hiba Shaban, Insing Na, Angelina A Kislichkina, Svetlana V Dentovskaya, Andrey P Anisimov, Vladimir N Uversky
The Yersinia pestis outer membrane porin F (OmpF) is a transmembrane protein located in the outer membrane of this Gram-negative bacterium which is the causative agent of plague, where it plays a significant role in controlling the selective permeability of the membrane. The amino acid sequences of OmpF proteins from 48 Y. pestis strains representing all currently available phylogenetic groups of this Gram-negative bacterium were recently deduced. Comparison of these amino acid sequences revealed that the OmpF can be present in four isoforms, the pestis-pestis type, and the pestis-microtus types I, II, and III...
September 3, 2016: Journal of Biomolecular Structure & Dynamics
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