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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
Jing Yang, Jiajia Yu, Jing Jiang, Chen Liang, Yongjun Feng
D-amino acids have been proved to disassemble biofilms by disassociating the matrix. Pantoea agglomerans is characterized by the formation of another kind of multicellular structure called symplasmata, which also remains the ability to form biofilms. In this study, a rice diazotrophic endophyte P. agglomerans YS19 was selected as a model strain to explore the effects of D-amino acids on these two kinds of cell aggregate structures. It was discovered that D-tyrosine disassociates biofilm, yet promotes symplasmata formation...
September 22, 2016: Journal of Basic Microbiology
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
Alita R Burmeister, Richard E Lenski, Justin R Meyer
The origin of new and complex structures and functions is fundamental for shaping the diversity of life. Such key innovations are rare because they require multiple interacting changes. We sought to understand how the adaptive landscape led to an innovation whereby bacteriophage λ evolved the new ability to exploit a receptor, OmpF, on Escherichia coli cells. Previous work showed that this ability evolved repeatedly, despite requiring four mutations in one virus gene. Here, we examine how this innovation evolved by studying six intermediate genotypes of λ isolated during independent transitions to exploit OmpF and comparing them to their ancestor...
September 28, 2016: Proceedings. Biological Sciences
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
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
Anna M Stenkova, Evgeniya P Bystritskaya, Konstantin V Guzev, Alexander V Rakin, Marina P Isaeva
The genus Yersinia includes species with a wide range of eukaryotic hosts (from fish, insects, and plants to mammals and humans). One of the major outer membrane proteins, the porin OmpC, is preferentially expressed in the host gut, where osmotic pressure, temperature, and the concentrations of nutrients and toxic products are relatively high. We consider here the molecular evolution and phylogeny of Yersinia ompC. The maximum likelihood gene tree reflects the macroevolution processes occurring within the genus Yersinia...
2016: Evolutionary Bioinformatics Online
Feng Zhao, Yongtao Wang, Haoran An, Yanling Hao, Xiaosong Hu, Xiaojun Liao
UNLABELLED: The formation of viable but nonculturable (VBNC) Escherichia coli O157:H7 induced by high-pressure CO2 (HPCD) was investigated using RNA sequencing (RNA-Seq) transcriptomics and isobaric tag for relative and absolute quantitation (iTRAQ) proteomic methods. The analyses revealed that 97 genes and 56 proteins were significantly changed upon VBNC state entry. Genes and proteins related to membrane transport, central metabolisms, DNA replication, and cell division were mainly downregulated in the VBNC cells...
2016: MBio
Matthias Bieligmeyer, Franjo Artukovic, Stephan Nussberger, Thomas Hirth, Thomas Schiestel, Michaela Müller
Structure and function of many transmembrane proteins are affected by their environment. In this respect, reconstitution of a membrane protein into a biomimetic polymer membrane can alter its function. To overcome this problem we used membranes formed by poly(1,4-isoprene-block-ethylene oxide) block copolymers blended with 1,2-diphytanoyl-sn-glycero-3-phosphocholine. By reconstituting the outer membrane protein OmpF from Escherichia coli into these membranes, we demonstrate functionality of this protein in biomimetic lipopolymer membranes, independent of the molecular weight of the block copolymers...
2016: Beilstein Journal of Nanotechnology
Wenwen Liu, Negar H Golshan, Xuliang Deng, Daniel J Hickey, Katherine Zeimer, Hongyi Li, Thomas J Webster
Since implants often fail due to infection and uncontrolled inflammatory responses, we designed an in vitro study to investigate the antibacterial and anti-inflammatory properties of titanium dioxide nanotubes (TNTs) incorporated with selenium nanoparticles (SeNPs). Selenium incorporation was achieved by the reaction of sodium selenite (Na2SeO3) with glutathione (GSH) under a vacuum in the presence of TNTs. Two types of bacteria and macrophages were cultured on the samples to determine their respective antibacterial and anti-inflammatory properties...
August 25, 2016: Nanoscale
María Queralt-Martín, Carlos Peiró-González, Marcel Aguilella-Arzo, Antonio Alcaraz
We combine electrophysiological experiments with the structure-based Poisson-Nernst-Planck 3D calculations to investigate the transport properties of the bacterial porin OmpF under large pH gradients and particularly low salt concentrations. We show that under extreme pH conditions protons and hydroxyls contribute decisively to the overall measured current, challenging the traditional interpretation of some electrokinetic parameters such as channel selectivity and rectification properties. We analyze with unprecedented detail the two intertwined factors ruling the ionic permeation through the channel, namely the differences between cation and anion mobilities and the electrostatic exclusion due to the interaction between permeating ions and channel ionizable residues...
August 3, 2016: Physical Chemistry Chemical Physics: PCCP
Anaïs Brosse, Anna Korobeinikova, Susan Gottesman, Maude Guillier
Two-component systems (TCS) and small regulatory RNAs (sRNAs) are both widespread regulators of gene expression in bacteria. TCS are in most cases transcriptional regulators. A large class of sRNAs act as post-transcriptional regulators of gene expression that modulate the translation and/or stability of target-mRNAs. Many connections have been recently unraveled between these two types of regulators, resulting in mixed regulatory circuits with poorly characterized properties. This study focuses on the negative feedback circuit that exists between the EnvZ-OmpR TCS and the OmrA/B sRNAs...
July 20, 2016: Nucleic Acids Research
Carlos G Leon-Velarde, Lotta Happonen, Maria Pajunen, Katarzyna Leskinen, Andrew M Kropinski, Laura Mattinen, Monika Rajtor, Joanna Zur, Darren Smith, Shu Chen, Ayesha Nawaz, Roger P Johnson, Joseph A Odumeru, Mansel W Griffiths, Mikael Skurnik
UNLABELLED: Bacteriophages present huge potential both as a resource for developing novel tools for bacterial diagnostics and for use in phage therapy. This potential is also valid for bacteriophages specific for Yersinia enterocolitica To increase our knowledge of Y. enterocolitica-specific phages, we characterized two novel yersiniophages. The genomes of the bacteriophages vB_YenM_TG1 (TG1) and vB_YenM_ϕR1-RT (ϕR1-RT), isolated from pig manure in Canada and from sewage in Finland, consist of linear double-stranded DNA of 162,101 and 168,809 bp, respectively...
September 1, 2016: Applied and Environmental Microbiology
Wanchana Ungphakorn, Thomas Tängdén, Linus Sandegren, Elisabet I Nielsen
OBJECTIVES: Resistant subpopulations with reduced expression of outer membrane porins have been observed in ESBL-producing Escherichia coli during exposure to ertapenem. The aim of this work was to develop a pharmacokinetic-pharmacodynamic (PKPD) model to characterize the emergence of resistant E. coli during exposure to ertapenem and to predict bacterial killing following different dosing regimens of ertapenem. METHODS: Data from in vitro time-kill experiments were used to develop a mechanism-based PKPD model for three E...
September 2016: Journal of Antimicrobial Chemotherapy
Mariano Andrea Scorciapino, Tommaso D'Agostino, Silvia Acosta-Gutierrez, Giuliano Malloci, Igor Bodrenko, Matteo Ceccarelli
BACKGROUND: In Gram-negative bacteria, the outer-membrane represents an additional barrier for antibiotics to permeate inside pathogens. Our inability to come up with novel effective antibiotics mostly relies upon insufficient understanding of the molecular basis behind outer-membrane penetration. RESULTS: Polar antibiotics can permeate through water-filled porins, such as OmpF and OmpC from Escherichia coli. Through molecular modeling, permeation of imipenem and meropenem was found to be strongly dependent upon capability of drugs to properly align their electric dipole to the internal electric field in the restricted region of the pore...
June 2016: Future Medicinal Chemistry
Nicolas Coudray, Ralph Lasala, Zhening Zhang, Kathy M Clark, Mark E Dumont, David L Stokes
Helical reconstruction represents a convenient and powerful approach for structure determination of macromolecules that assemble into helical arrays. In the case of membrane proteins, formation of tubular crystals with helical symmetry represents an attractive alternative, especially when their small size precludes the use of single-particle analysis. An essential first step for helical reconstruction is to characterize the helical symmetry. This process is often daunting, due to the complexity of helical diffraction and to the low signal-to-noise ratio in images of individual assemblies...
August 2016: Journal of Structural Biology
Hui Huang, Yawei Sun, Li Yuan, Yushan Pan, Yanlin Gao, Caihui Ma, Gongzheng Hu
The two-component signal transduction system CpxAR is especially widespread in Gram-negative bacteria. It has been reported that CpxAR contributes to the multidrug resistance (MDR) in Escherichia coli. CpxR is a response regulator in the two-component CpxAR system. The aim of this study was to explore the role of cpxR in the MDR of S. enterica serovar Typhimurium. The minimal inhibitory concentrations (MICs) of various antibiotics commonly used in veterinary medicine for strains JS (a multidrug-susceptible standard strain of S...
2016: Frontiers in Microbiology
Colleen R Eade, Chien-Che Hung, Brian Bullard, Geoffrey Gonzalez-Escobedo, John S Gunn, Craig Altier
Salmonella spp. are carried by and can acutely infect agricultural animals and humans. After ingestion, salmonellae traverse the upper digestive tract and initiate tissue invasion of the distal ileum, a virulence process carried out by the type III secretion system encoded within Salmonella pathogenicity island 1 (SPI-1). Salmonellae coordinate SPI-1 expression with anatomical location via environmental cues, one of which is bile, a complex digestive fluid that causes potent repression of SPI-1 genes. The individual components of bile responsible for SPI-1 repression have not been previously characterized, nor have the bacterial signaling processes that modulate their effects been determined...
August 2016: Infection and Immunity
Annika Heininger, Rahmi Yusuf, Robert J Lawrence, Roger R Draheim
The Escherichia coli sensor kinase EnvZ modulates porin expression in response to various stimuli, including extracellular osmolarity, the presence of procaine and interaction with an accessory protein, MzrA. Two major outer membrane porins, OmpF and OmpC, act as passive diffusion-limited pores that allow compounds, including certain classes of antibiotics such as β-lactams and fluoroquinolones, to enter the bacterial cell. Even though the mechanisms by which EnvZ detects and processes the presence of various stimuli are a fundamental component of microbial physiology, they are not yet fully understood...
August 2016: Biochimica et Biophysica Acta
Ling-Fu Huang, Chao-Tai Lee, Lin-Hui Su, Chin-Lu Chang
Enterobacter cloacae is one of the most common carbapenem-resistant Enterobacteriaceae (CRE) global wide. Resistance to tigecycline, one of the few therapeutic options for CRE infections, in carbapenem-resistant E. cloacae is of clinical significance. Fourteen E. cloacae clinical isolates (EC1-EC14) co-resistant to tigecycline and carbapenems were studied. Two tigecycline-susceptible/carbapenem-resistant isolates (TS1-TS2) were used for comparison. Genotyping by pulsed-field gel electrophoresis and multilocus sequence typing identified seven pulsotypes and three sequence types (STs)...
May 2, 2016: Microbial Drug Resistance: MDR: Mechanisms, Epidemiology, and Disease
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