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https://www.readbyqxmd.com/read/29350941/immotile-active-matter-activity-from-death-and-reproduction
#1
Arben Kalziqi, David Yanni, Jacob Thomas, Siu Lung Ng, Skanda Vivek, Brian K Hammer, Peter J Yunker
Unlike equilibrium atomic solids, biofilms-soft solids composed of bacterial cells-do not experience significant thermal fluctuations at the constituent level. However, living cells stochastically reproduce and die, provoking a mechanical response. We investigate the mechanical consequences of cellular death and reproduction by measuring surface-height fluctuations of biofilms containing two mutually antagonistic strains of Vibrio cholerae that kill one another on contact via the type VI secretion system. While studies of active matter typically focus on activity via constituent mobility, here, activity is mediated by reproduction and death events in otherwise immobilized cells...
January 5, 2018: Physical Review Letters
https://www.readbyqxmd.com/read/29349568/class-iii-bacteriocin-helveticin-m-causes-sublethal-damage-on-target-cells-through-impairment-of-cell-wall-and-membrane
#2
Zhilan Sun, Xiaomeng Wang, Xinxiao Zhang, Haihong Wu, Ye Zou, Pengpeng Li, Chong Sun, Weimin Xu, Fang Liu, Daoying Wang
Helveticin-M, a novel Class III bacteriocin produced by Lactobacillus crispatus exhibited an antimicrobial activity against Staphylococcus aureus, S. saprophyticus, and Enterobacter cloacae. To understand how Helveticin-M injured target cells, Helveticin-M was cloned and heterologously expressed in Escherichia coli. Subsequently, the cell wall organization and cell membrane integrity of target cells were determined. The mechanism of cellular damage differed according to bacterial species. Based on morphology analysis, Helveticin-M disrupted the cell wall of Gram-positive bacteria and disorganized the outer membrane of Gram-negative bacteria, therefore, altering surface structure...
January 18, 2018: Journal of Industrial Microbiology & Biotechnology
https://www.readbyqxmd.com/read/29348582/nanostructured-titanium-surfaces-exhibit-recalcitrance-towards-staphylococcus-epidermidis-biofilm-formation
#3
Yunyi Cao, Bo Su, Subash Chinnaraj, Saikat Jana, Leon Bowen, Sam Charlton, Pengfei Duan, Nicholas S Jakubovics, Jinju Chen
Titanium-based implants are ubiquitous in the healthcare industries and often suffer from bacterial attachment which results in infections. An innovative method of reducing bacterial growth is to employ nanostructures on implant materials that cause contact-dependent cell death by mechanical rupture of bacterial cell membranes. To achieve this, we synthesized nanostructures with different architectures on titanium surfaces using hydrothermal treatment processes and then examined the growth of Staphylococcus epidermidis on these surfaces...
January 18, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29348168/the-phospholipid-repair-system-lplt-aas-in-gram-negative-bacteria-protects-the-bacterial-membrane-envelope-from-host-phospholipase-a2-attack
#4
Yibin Lin, Mikhail Bogdanov, Shuo Lu, Ziqiang Guan, William Margolin, Jerrold P Weiss, Lei Zheng
Secretory phospholipases A2 (sPLA2) are potent components of mammalian innate-immunity antibacterial mechanisms. sPLA2 enzymes attack bacteria by hydrolyzing bacterial membrane phospholipids, causing membrane disorganization and cell lysis. However, most Gram-negative bacteria are naturally resistant to sPLA2. Here we report a novel resistance mechanism to mammalian sPLA2 in Escherichia coli, mediated by a phospholipid repair system consisting of the lysophospholipid transporter LplT and the acyltransferase Aas in the cytoplasmic membrane...
January 18, 2018: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/29348055/high-resolution-structures-of-mitochondrial-ribosomes-and-their-functional-implications
#5
REVIEW
Philipp Bieri, Basil J Greber, Nenad Ban
Mitochondrial ribosomes (mitoribosomes) almost exclusively synthesize essential components of the oxidative phosphorylation machinery. Dysfunction of mitochondrial protein biosynthesis leads to human diseases and plays an important role in the altered metabolism of cancer cells. Recent developments in cryo-electron microscopy enabled the structural characterization of complete yeast and mammalian mitoribosomes at near-atomic resolution. Despite originating from ancestral bacterial ribosomes, mitoribosomes have diverged in their composition and architecture...
January 15, 2018: Current Opinion in Structural Biology
https://www.readbyqxmd.com/read/29347628/opposing-effects-of-cationic-antimicrobial-peptides-and-divalent-cations-on-bacterial-lipopolysaccharides
#6
Matthew Smart, Aruna Rajagopal, Wing-Ki Liu, Bae-Yeun Ha
The permeability of the bacterial outer membrane, enclosing Gram-negative bacteria, depends on the interactions of the outer, lipopolysaccharide (LPS) layer, with surrounding ions and molecules. We present a coarse-grained model for describing how cationic amphiphilic molecules (e.g., antimicrobial peptides) interact with and perturb the LPS layer in a biologically relevant medium, containing monovalent and divalent salt ions (e.g., Mg^{2+}). In our approach, peptide binding is driven by electrostatic and hydrophobic interactions and is assumed to expand the LPS layer, eventually priming it for disruption...
October 2017: Physical Review. E
https://www.readbyqxmd.com/read/29346438/colonization-of-the-cervicovaginal-space-with-gardnerella-vaginalis-leads-to-local-inflammation-and-cervical-remodeling-in-pregnant-mice
#7
Luz-Jeannette Sierra, Amy G Brown, Guillermo O Barilá, Lauren Anton, Carrie E Barnum, Snehal S Shetye, Louis J Soslowsky, Michal A Elovitz
The role of the cervicovaginal (CV) microbiome in regulating cervical function during pregnancy is poorly understood. Gardnerella vaginalis (G. vaginalis) is the most common bacteria associated with the diagnosis of bacterial vaginosis (BV). While BV has been associated with preterm birth (PTB), clinical trials targeting BV do not decrease PTB rates. It remains unknown if G. vaginalis is capable of triggering molecular, biomechanical and cellular events that could lead to PTB. The objective of this study was to determine if cervicovaginal colonization with G...
2018: PloS One
https://www.readbyqxmd.com/read/29346329/anti-phytopathogenic-and-cytotoxic-activities-of-crude-extracts-and-secondary-metabolites-of-marine-derived-fungi
#8
Dong-Lin Zhao, Dan Wang, Xue-Ying Tian, Fei Cao, Yi-Qiang Li, Cheng-Sheng Zhang
Thirty-one isolates belonging to eight genera in seven orders were identified from 141 strains that were isolated from several marine plants. Alternaria sp. and Fusarium sp. were found to be the predominant fungi. Evaluation of the anti-phytopathogenic bacterial and fungal activities, as well as the cytotoxicity of these 31 extracts, revealed that most of them displayed different levels of bioactivities. Due to their interesting bioactivities, two fungal strains-Fusarium equiseti (P18) and Alternaria sp. (P8)-were selected for chemical investigation and compounds 1-4 were obtained...
January 18, 2018: Marine Drugs
https://www.readbyqxmd.com/read/29345850/effects-of-glutaraldehyde-didecyldimethylammonium-bromide-combined-disinfectant-on-the-cell-surface-of-staphylococcus-aureus
#9
Wenshu Lin, Jialin Yi, Yuelin Zhang, Zhirui Deng, Qin Chen, Bing Niu
AIMS: The effects of a new glutaraldehyde-didecyldimethylammonium bromide combination disinfectant (GD) on the cell surface of Staphylococcus aureus, a representative Gram-positive bacterium, were investigated in this study. METHODS AND RESULTS: Results of bacterial surface structural analysis showed that GD significantly changed the bacterial morphology. The membrane fluidity decreased and outer membrane permeabilization increased after contact with GD. Furthermore, the integrity of the cytoplasmic membrane was destroyed by over 99% after exposure to GD for a short time...
January 18, 2018: Journal of Applied Microbiology
https://www.readbyqxmd.com/read/29345379/sphingolipids-role-in-the-regulation-of-inflammatory-response-from-leukocyte-biology-to-bacterial-infection
#10
REVIEW
Elena Chiricozzi, Nicoletta Loberto, Domitilla Schiumarini, Maura Samarani, Giulia Mancini, Anna Tamanini, Giuseppe Lippi, Maria Cristina Dechecchi, Rosaria Bassi, Paola Giussani, Massimo Aureli
Sphingolipids (SLs) are amphiphilic molecules mainly associated with the external leaflet of eukaryotic plasma membrane, and are structural membrane components with key signaling properties. Since the beginning of the last century, a large number of papers described the involvement of these molecules in several aspects of cell physiology and pathology. Several lines of evidence support the critical role of SLs in inflammatory diseases, by acting as anti- or pro-inflammatory mediators. They are involved in control of leukocyte activation and migration, and are recognized as essential players in host response to pathogenic infection...
January 9, 2018: Journal of Leukocyte Biology
https://www.readbyqxmd.com/read/29344915/mechanistic-investigation-of-visible-light-driven-photocatalytic-inactivation-of-e-coli-by-ag-agcl-znfe2o4
#11
Akhanda Raj Upreti, Nirina Khadgi, Yi Li
In this study, photocatalytic inactivation of Escherichia coli was investigated over magnetic nanocomposite Ag-AgCl/ZnFe2O4. The nanocomposite demonstrated efficient photocatalytic activity by complete inactivation of the bacteria within 60 min of visible light irradiation. The anions HPO42- and SO42- were found to play the most important role in the inhibition of photocatalytic inactivation of E. coli. A systematic investigation of mechanism of photocatalytic bacterial inactivation was carried out based on cell membrane injury test, scanning electron microscopy (SEM) of bacterial morphology changes, Fourier transform infrared (FTIR) spectroscopy of E...
January 17, 2018: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/29343818/a-surfactant-polymer-dressing-potentiates-antimicrobial-efficacy-in-biofilm-disruption
#12
Piya Das Ghatak, Shomita S Mathew-Steiner, Priyanka Pandey, Sashwati Roy, Chandan K Sen
A 100% water-soluble surfactant polymer dressing (SPD) that is bio-compatible and non-ionic has been reported to improve wound closure in preliminary clinical studies. The mechanism of action of SPD in wound healing remains unclear. Biofilm infection is a significant problem that hinders proper wound closure. The objective of this study was to characterize the mechanism of action of SPD inhibition of bacterial biofilm development. Static biofilms (48 h) of the primary wound pathogens Pseudomonas aeruginosa (PA01), Staphylococcus aureus (USA300) were grown on polycarbonate membranes and treated with SPD with and without antibiotics for an additional 24 h...
January 17, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29343670/anti-sigma-factor-mediated-cell-surface-stress-responses-in-bacillus-subtilis
#13
Kei Asai
Proteins belonging to the sigma factor family in eubacteria initiate transcription by associating with RNA polymerase. A subfamily, the extracytoplasmic function (ECF) sigma factors, which form a widely distributed bacterial signal transduction system comprising a sigma factor and a cognate membrane-embedded anti-sigma factor, regulates genes in response to stressors that threaten cell envelope integrity including the cell wall and membrane. The Gram-positive soil bacterium Bacillus subtilis provides a valuable model for investigation of the ECF sigma factors...
January 17, 2018: Genes & Genetic Systems
https://www.readbyqxmd.com/read/29343668/configuration-of-the-sugar-head-of-glycolipids-in-thylakoid-membranes
#14
Egi Tritya Apdila, Koichiro Awai
Glycolipids constitute the majority of membrane components in oxygenic photosynthetic organisms, whereas they are minor lipids in other organisms. In cyanobacteria, three glycolipids comprise ~90 mol% of the total lipids in thylakoid membranes, where photosynthetic electron transport occurs. Among these glycolipids, 80 mol% are galactolipids (monogalactosyldiacylglycerol and digalactosyldiacylglycerol). Galactolipids are well conserved in oxygenic photosynthetic organisms and are believed to be essential for the integrity of the membrane system...
January 17, 2018: Genes & Genetic Systems
https://www.readbyqxmd.com/read/29343645/crystal-structure-of-the-mammalian-lipopolysaccharide-detoxifier
#15
Alexei Gorelik, Katalin Illes, Bhushan Nagar
LPS is a potent bacterial endotoxin that triggers the innate immune system. Proper recognition of LPS by pattern-recognition receptors requires a full complement of typically six acyl chains in the lipid portion. Acyloxyacyl hydrolase (AOAH) is a host enzyme that removes secondary (acyloxyacyl-linked) fatty acids from LPS, rendering it immunologically inert. This activity is critical for recovery from immune tolerance that follows Gram-negative infection. To understand the molecular mechanism of AOAH function, we determined its crystal structure and its complex with LPS...
January 17, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/29343618/retention-of-acholeplasma-laidlawii-by-sterile-filtration-membranes-effect-of-cultivation-medium-and-filtration-temperature
#16
Alexander Helling, Hannes König, Felix Seiler, Ralph Berkholz, Volkmar Thom, Milan Polakovic
This experimental study compares cell size, zeta potential and the ability to penetrate tailor-made size exclusion membrane filters of mycoplasma A. laidlawii cultivated in five different cultivation media. The influence of relevant filtration process parameters, in particular transmembrane pressure and filtration temperature, on their respective retention was tested. The impact of the filtration temperature was further evaluated for the Gram-negative bacteria species Brevundimonas diminuta, the Gram-positive bacteria species Staphylococcus epidermidis, the Pseudomonas phage PP7 and the mycoplasma species M...
January 17, 2018: PDA Journal of Pharmaceutical Science and Technology
https://www.readbyqxmd.com/read/29342349/membrane-allostery-and-unique-hydrophobic-sites-promote-enzyme-substrate-specificity
#17
Varnavas D Mouchlis, Yuan Chen, J Andrew McCammon, Edward A Dennis
We demonstrate that lipidomics coupled with molecular dynamics reveals unique phospholipase A2 specificity toward membrane phospholipid substrates. We discovered unexpected head-group and acyl-chain specificity for three-major human phospholipases A2. These differences between each enzyme's specificity coupled with molecular dynamicsbased structural and binding studies revealed unique active site and interfacial surface binding moieties for each enzyme that explains the observed specificity at a hitherto inaccessible structural level...
January 17, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29342145/the-gram-negative-bacterial-periplasm-size-matters
#18
Samuel I Miller, Nina R Salama
Gram-negative bacteria are surrounded by two membrane bilayers separated by a space termed the periplasm. The periplasm is a multipurpose compartment separate from the cytoplasm whose distinct reducing environment allows more efficient and diverse mechanisms of protein oxidation, folding, and quality control. The periplasm also contains structural elements and important environmental sensing modules, and it allows complex nanomachines to span the cell envelope. Recent work indicates that the size or intermembrane distance of the periplasm is controlled by periplasmic lipoproteins that anchor the outer membrane to the periplasmic peptidoglycan polymer...
January 2018: PLoS Biology
https://www.readbyqxmd.com/read/29340775/global-versus-local-mechanisms-of-temperature-sensing-in-ion-channels
#19
REVIEW
Cristina Arrigoni, Daniel L Minor
Ion channels turn diverse types of inputs, ranging from neurotransmitters to physical forces, into electrical signals. Channel responses to ligands generally rely on binding to discrete sensor domains that are coupled to the portion of the channel responsible for ion permeation. By contrast, sensing physical cues such as voltage, pressure, and temperature arises from more varied mechanisms. Voltage is commonly sensed by a local, domain-based strategy, whereas the predominant paradigm for pressure sensing employs a global response in channel structure to membrane tension changes...
January 17, 2018: Pflügers Archiv: European Journal of Physiology
https://www.readbyqxmd.com/read/29340383/alamethicin-self-assembling-in-lipid-membranes-concentration-dependence-from-pulsed-epr-of-spin-labels
#20
Victoria N Syryamina, Marta De Zotti, Claudio Toniolo, Fernando Formaggio, Sergei A Dzuba
The antimicrobial action of the peptide antibiotic alamethicin (Alm) is commonly related to peptide self-assembling resulting in the formation of voltage-dependent channels in bacterial membranes, which induces ion permeation. To obtain a deeper insight into the mechanism of channel formation, it is useful to know the dependence of self-assembling on peptide concentration. With this aim, we studied Alm F50/5 spin-labeled analogs in a model 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membrane, for peptide-to-lipid (P/L) ratios varying between 1/1500 and 1/100...
January 17, 2018: Physical Chemistry Chemical Physics: PCCP
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