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Ursula N Broder, Tina Jaeger, Urs Jenal
Virulence of pathogenic bacteria is a tightly controlled process to facilitate invasion and survival in host tissues. Although pathways controlling virulence have been defined in detail, signals modulating these processes are poorly understood. The opportunistic pathogen Pseudomonas aeruginosa causes acute and chronic infections in humans. Disease progression is typically associated with a loss of acute virulence and the emergence of biofilms and chronic behaviour. The acute-to-chronic switch is governed by the global Gac/Rsm pathway...
October 24, 2016: Nature Microbiology
Florian Graef, Branko Vukosavljevic, Jean-Philippe Michel, Marius Wirth, Oliver Ries, Chiara De Rossi, Maike Windbergs, Véronique Rosilio, Christian Ducho, Sarah Gordon, Claus-Michael Lehr
Gram-negative bacteria possess a unique and complex cell envelope, composed of an inner and outer membrane separated by an intermediate cell wall-containing periplasm. This tripartite structure acts intrinsically as a significant biological barrier, often limiting the permeation of anti-infectives, and so preventing such drugs from reaching their target. Furthermore, identification of the specific permeation-limiting envelope component proves difficult in the case of many anti-infectives, due to the challenges associated with isolation of individual cell envelope structures in bacterial culture...
October 18, 2016: Journal of Controlled Release: Official Journal of the Controlled Release Society
Narges Abdali, Jerry Matthew Parks, Keith Haynes, Julie L Chaney, Adam T Green, David Wolloscheck, John K Walker, Valentin V Rybenkov, Jerome Yves Baudry, Jeremy C Smith, Helen I Zgurskaya
Antibiotic resistance is a major threat to human welfare. Inhibitors of multidrug efflux pumps (EPIs) are promising alternative therapeutics that could revive activities of antibiotics and reduce bacterial virulence. Identification of new druggable sites for inhibition is critical for development of effective EPIs, especially in light of constantly emerging resistance. Here, we describe EPIs that interact with periplasmic membrane fusion proteins, critical components of efflux pumps that are responsible for the activation of the transporter and the recruitment of the outer-membrane channel...
October 21, 2016: ACS Infectious Diseases
Haseong Kim, Gui Hwan Han, Yaoyao Fu, Jongsik Gam, Seung Goo Lee
Recent improvements in Förster resonance energy transfer (FRET) sensors have enabled their use to detect various small molecules including ions and amino acids. However, the innate weak signal intensity of FRET sensors is a major challenge that prevents their application in various fields and makes the use of expensive, high-end fluorometers necessary. Previously, we built a cost-effective, high-performance FRET analyzer that can specifically measure the ratio of two emission wavelength bands (530 and 480 nm) to achieve high detection sensitivity...
October 1, 2016: Journal of Visualized Experiments: JoVE
Mark Shepherd, Maud E S Achard, Adi Idris, Makrina Totsika, Minh-Duy Phan, Kate M Peters, Sohinee Sarkar, Cláudia A Ribeiro, Louise V Holyoake, Dimitrios Ladakis, Glen C Ulett, Matthew J Sweet, Robert K Poole, Alastair G McEwan, Mark A Schembri
Nitric oxide (NO) is a toxic free radical produced by neutrophils and macrophages in response to infection. Uropathogenic Escherichia coli (UPEC) induces a variety of defence mechanisms in response to NO, including direct NO detoxification (Hmp, NorVW, NrfA), iron-sulphur cluster repair (YtfE), and the expression of the NO-tolerant cytochrome bd-I respiratory oxidase (CydAB). The current study quantifies the relative contribution of these systems to UPEC growth and survival during infection. Loss of the flavohemoglobin Hmp and cytochrome bd-I elicit the greatest sensitivity to NO-mediated growth inhibition, whereas all but the periplasmic nitrite reductase NrfA provide protection against neutrophil killing and promote survival within activated macrophages...
October 21, 2016: Scientific Reports
Norah Lynn-Anne Mund, Wycliffe Omurwa Masanta, Anne-Marie Goldschmidt, Raimond Lugert, Uwe Groß, Andreas E Zautner
Campylobacter jejuni's flagellar locomotion is controlled by eleven chemoreceptors. Assessment of the distribution of the relevant chemoreceptor genes in the C. jejuni genomes deposited in the National Center for Biotechnology Information (NCBI) database led to the identification of two previously unknown tlp genes and a tlp5 pseudogene. These two chemoreceptor genes share the same locus in the C. jejuni genome with tlp4 and tlp11, but the gene region encoding the periplasmic ligand binding domain differs significantly from other chemoreceptor genes...
September 29, 2016: European Journal of Microbiology & Immunology
Kyle A Tipton, Marjan Farokhyfar, Philip N Rather
Colony opacity phase variation in Acinetobacter baumannii strain AB5075 is regulated by a reversible high-frequency switch. Transposon mutagenesis was used to generate mutations that decreased the opaque to translucent switch and a gene encoding a predicted periplasmic membrane fusion component of a resistance-nodulation-cell division (RND)-type efflux system was isolated. This gene was designated arpA and immediately downstream was a gene designated arpB that encodes a predicted membrane transporter of RND-type systems...
October 19, 2016: MicrobiologyOpen
Maite L Ortiz-Suarez, Firdaus Samsudin, Thomas J Piggot, Peter J Bond, Syma Khalid
OmpA is a multidomain protein found in the outer membranes of most Gram-negative bacteria. Despite a wealth of reported structural and biophysical studies, the structure-function relationships of this protein remain unclear. For example, it is still debated whether it functions as a pore, and the precise molecular role it plays in attachment to the peptidoglycan of the periplasm is unknown. The absence of a consensus view is partly due to the lack of a complete structure of the full-length protein. To address this issue, we performed molecular-dynamics simulations of the full-length model of the OmpA dimer proposed by Robinson and co-workers...
October 18, 2016: Biophysical Journal
Antonino Baez, Joseph Shiloach
The damaging effect of high oxygen concentration on growth of Escherichia coli is well established. Over-oxygenation increases the intracellular concentration of reactive oxygen species (ROS), causing the destruction of the [4Fe-4S] cluster of dehydratases and limiting the biosynthesis of both branched-chain amino acids and nicotinamide adenine dinucleotide. A key enzyme that reduces the damaging effect of superoxide is superoxide dismutase (SOD). Its transcriptional regulation is controlled by global transcription regulators that respond to changes in oxygen and iron concentrations and pH...
October 18, 2016: Antonie Van Leeuwenhoek
Irfan Ahmad, Syed Fazle Rouf, Lei Sun, Annika Cimdins, Sulman Shafeeq, Soazig Le Guyon, Marco Schottkowski, Mikael Rhen, Ute Römling
BACKGROUND: Cellulose, a 1,4 beta-glucan polysaccharide, is produced by a variety of organisms including bacteria. Although the production of cellulose has a high biological, ecological and economical impact, regulatory mechanisms of cellulose biosynthesis are mostly unknown. Family eight cellulases are regularly associated with cellulose biosynthesis operons in bacteria; however, their function is poorly characterized. In this study, we analysed the role of the cellulase BcsZ encoded by the bcsABZC cellulose biosynthesis operon of Salmonella enterica serovar Typhimurium (S...
October 19, 2016: Microbial Cell Factories
Laura M Faure, Jean-Bernard Fiche, Leon Espinosa, Adrien Ducret, Vivek Anantharaman, Jennifer Luciano, Sébastien Lhospice, Salim T Islam, Julie Tréguier, Mélanie Sotes, Erkin Kuru, Michael S Van Nieuwenhze, Yves V Brun, Olivier Théodoly, Aravind L, Marcelo Nollmann, Tâm Mignot
Various rod-shaped bacteria mysteriously glide on surfaces in the absence of appendages such as flagella or pili. In the deltaproteobacterium Myxococcus xanthus, a putative gliding motility machinery (Agl-Glt) localizes to so-called Focal Adhesion sites (FA) that form stationary contact points with the underlying surface. We discovered that the Agl-Glt machinery contains an inner-membrane motor complex that moves intracellularly along a right-handed helical path, and when it becomes stationary at FA sites, it powers a left-handed rotation of the cell around its long axis...
October 5, 2016: Nature
Benjamin A Webb, K Karl Compton, Rafael Castañeda Saldaña, Timofey Arapov, W Keith Ray, Richard F Helm, Birgit E Scharf
The bacterium Sinorhizobium meliloti is attracted to seed exudates of its host plant alfalfa (Medicago sativa). Since quaternary ammonium compounds (QACs) are exuded by germinating seeds, we assayed chemotaxis of S. meliloti towards betonicine, choline, glycine betaine, stachydrine, and trigonelline. The wild type displayed a positive response to all QACs. Using LC-MS, we determined that each germinating alfalfa seed exuded QACs in the nanogram range. Compared to the closely related non-host species, spotted medic (Medicago arabica), unique profiles were released...
October 17, 2016: Molecular Microbiology
F H Matsubara, G O Meissner, V Herzig, H C Justa, B C L Dias, D Trevisan-Silva, L H Gremski, W Gremski, A Senff-Ribeiro, O M Chaim, G F King, S S Veiga
Loxosceles intermedia venom comprises a complex mixture of proteins, glycoproteins and low molecular mass peptides that act synergistically to immobilize envenomed prey. Analysis of a venom-gland transcriptome from L. intermedia revealed that knottins, also known as inhibitor cystine knot peptides, are the most abundant class of toxins expressed in this species. Knottin peptides contain a particular arrangement of intramolecular disulphide bonds, and these peptides typically act upon ion channels or receptors in the insect nervous system, triggering paralysis or other lethal effects...
October 15, 2016: Insect Molecular Biology
Yu Yang, Wendy Ballent, Brooke K Mayer
Phosphorus (P) is a critical, nonrenewable nutrient; yet excess discharges can lead to eutrophication and deterioration of water quality. Thus, P removal from water must be coupled with P recovery to achieve sustainable P management. P-specific proteins provide a novel, promising approach to recover P from water. Bacterial phosphate binding proteins (PBP) are able to effectively remove phosphate, achieving extremely low levels in water (i.e., 0.015 mg-P L(-1)). A prerequisite of using PBP for P recovery, however, is not only removal, but also controlled P release, which has not yet been reported...
October 14, 2016: FEMS Microbiology Letters
Dimitri Chérier, Sean Giacomucci, Delphine Patin, Ahmed Bouhss, Thierry Touzé, Didier Blanot, Dominique Mengin-Lecreulx, Hélène Barreteau
Colicins are bacterial toxins produced by some Escherichia coli strains. They exhibit either enzymatic or pore-forming activity towards a very limited number of bacterial species, due to the high specificity of their reception and translocation systems. Yet, we succeeded in making the colicin M homologue from Pectobacterium carotovorum, pectocin M1 (PcaM1), capable of inhibiting E. coli cell growth by bypassing these reception and translocation steps. This goal was achieved through periplasmic expression of this pectocin...
October 8, 2016: Antibiotics
Aleksandra Margetić, Zoran Vujčić
Yeast Saccharomyces cerevisiae is the most significant source of enzyme invertase. It is mainly used in the food industry as a soluble or immobilized enzyme. The greatest amount of invertase is located in the periplasmic space in yeast. In this work it was isolated two forms of enzyme from yeastS. cerevisiae cell, soluble and cell wall invertase (CWI). Both forms of enzyme showed same temperature optimum (60°C), similar pH optimum and kinetic parameters. The significant difference between these biocatalysts was observed in their thermal stability, stability in urea and methanol solution...
October 13, 2016: Preparative Biochemistry & Biotechnology
Juan Manuel Belardinelli, Amira Yazidi, Liang Yang, Lucien Fabre, Wei Li, Benoit Jacques, Shiva Kumar Angala, Isabelle Rouiller, Helen I Zgurskaya, Jurgen Sygusch, Mary Jackson
The MmpL family of proteins translocates complex (glyco)lipids and siderophores across the cell envelope of mycobacteria and closely related Corynebacteriaceae and plays important roles in the biogenesis of the outer membrane of these organisms. Despite their significance in the physiology and virulence of Mycobacterium tuberculosis, and from the perspective of developing novel antituberculosis agents, little is known about their structure and mechanism of translocation. In this study, the essential mycobacterial mycolic acid transporter, MmpL3, and its orthologue in Corynebacterium glutamicum, CmpL1, were investigated as prototypical MmpL proteins to gain insight into the transmembrane topology, tertiary and quaternary structures, and functional regions of this transporter family...
October 14, 2016: ACS Infectious Diseases
Sarah K McDonald, Karen Gibson Fleming
Hysteresis in equilibrium protein folding titrations is an experimental barrier that must be overcome to extract meaningful thermodynamic quantities. Traditional approaches to solving this problem involve testing a spectrum of solution conditions to find ones that achieve path independence. Through this procedure, a specific pH of 3.8 was required to achieve path-independence for the water-to-bilayer equilibrium folding of outer membrane protein OmpLA. We hypothesized that the neutralization of negatively charged side chains (Asp and Glu) at pH 3...
October 12, 2016: Biochemistry
Chanchal Kumar, Jitendra Wagh, G Archana, G Naresh Kumar
Enterobacter asburiae PSI3 solubilizes mineral phosphates in the presence of glucose by the secretion of gluconic acid generated by the action of a periplasmic pyrroloquinoline quinone dependent glucose dehydrogenase. In order to achieve mineral phosphate solubilization phenotype in the presence of sucrose, plasmids pCNK4 and pCNK5 containing genes encoding the invertase enzyme of Zymomonas mobilis (invB) and of Saccharomyces cerevisiae (suc2) under constitutive promoters were constructed with malE signal sequence (in case of invB alone as the suc2 is secreted natively)...
December 2016: World Journal of Microbiology & Biotechnology
J Szewczyk, J-F Collet
Bacterial lipoproteins are a very diverse group of proteins characterized by the presence of an N-terminal lipid moiety that serves as a membrane anchor. Lipoproteins have a wide variety of crucial functions, ranging from envelope biogenesis to stress response. In Gram-negative bacteria, lipoproteins can be targeted to various destinations in the cell, including the periplasmic side of the cytoplasmic or outer membrane, the cell surface or the external milieu. The sorting mechanisms have been studied in detail in Escherichia coli, but exceptions to the rules established in this model bacterium exist in other bacteria...
2016: Advances in Microbial Physiology
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