scholarly journals Important Late-Stage Symbiotic Role of theSinorhizobium melilotiExopolysaccharide Succinoglycan

2018 ◽  
Vol 200 (13) ◽  
pp. e00665-17 ◽  
Author(s):  
Markus F. F. Arnold ◽  
Jon Penterman ◽  
Mohammed Shabab ◽  
Esther J. Chen ◽  
Graham C. Walker
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Late Stage ◽  
Sinorhizobium Meliloti ◽  
Antimicrobial Action ◽  
Protective Function ◽  
Content Type ◽  
Early Stages ◽  
Symbiotic Interactions ◽  
Legume Symbiosis

ABSTRACTSinorhizobium melilotienters into beneficial symbiotic interactions withMedicagospecies of legumes. Bacterial exopolysaccharides play critical signaling roles in infection thread initiation and growth during the early stages of root nodule formation. After endocytosis ofS. melilotiby plant cells in the developing nodule, plant-derived nodule-specific cysteine-rich (NCR) peptides mediate terminal differentiation of the bacteria into nitrogen-fixing bacteroids. Previous transcriptional studies showed that the intensively studied cationic peptide NCR247 induces expression of theexogenes that encode the proteins required for succinoglycan biosynthesis. In addition, genetic studies have shown that someexomutants exhibit increased sensitivity to the antimicrobial action of NCR247. Therefore, we investigated whether the symbiotically activeS. melilotiexopolysaccharide succinoglycan can protectS. melilotiagainst the antimicrobial activity of NCR247. We discovered that high-molecular-weight forms of succinoglycan have the ability to protectS. melilotifrom the antimicrobial action of the NCR247 peptide but low-molecular-weight forms of wild-type succinoglycan do not. The protective function of high-molecular-weight succinoglycan occurs via direct molecular interactions between anionic succinoglycan and the cationic NCR247 peptide, but this interaction is not chiral. Taken together, our observations suggest thatS. melilotiexopolysaccharides not only may be critical during early stages of nodule invasion but also are upregulated at a late stage of symbiosis to protect bacteria against the bactericidal action of cationic NCR peptides. Our findings represent an important step forward in fully understanding the complete set of exopolysaccharide functions during legume symbiosis.IMPORTANCESymbiotic interactions between rhizobia and legumes are economically important for global food production. The legume symbiosis also is a major part of the global nitrogen cycle and is an ideal model system to study host-microbe interactions. Signaling between legumes and rhizobia is essential to establish symbiosis, and understanding these signals is a major goal in the field. Exopolysaccharides are important in the symbiotic context because they are essential signaling molecules during early-stage symbiosis. In this study, we provide evidence suggesting that theSinorhizobium melilotiexopolysaccharide succinoglycan also protects the bacteria against the antimicrobial action of essential late-stage symbiosis plant peptides.

SiO2 modified graphene oxide hybrids for improving fretting wear performance of ultra-high molecular weight polyethylene

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiaocui Xin ◽  
Yunxia Wang ◽  
Zhaojie Meng ◽  
Fengyuan Yan
Keyword(s):  
Molecular Weight ◽  
Wear Resistance ◽  
High Molecular Weight ◽  
Design Methodology ◽  
Fretting Wear ◽  
Wear Performance ◽  
Content Type ◽  
Modified Graphene Oxide ◽  
Modified Graphene ◽  
Ultra High Molecular Weight

Purpose The purpose of this paper is to investigate the fretting wear performance of ultra-high-molecular-weight-polyethene (UHMWPE) with addition of GO and SiO2. Design/methodology/approach In this study, GO were synthesized and SiO2 nanoparticles were grafted onto GO. The effect of nanofiller on fretting wear performance of UHMWPE was investigated. Findings The results indicated that GO was successfully synthesized and SiO2 nanoparticles successfully grafted onto GO. Incorporation of GS was beneficial for the reduction in friction and the improvement in wear resistance of UHMWPE. GO was beneficial for reducing friction coefficient, while SiO2 was good for improving wear resistance. There existed a tribological synergistic effect between GO nanosheet and SiO2 nanoparticles. Research limitations/implications The hybrids of GS were promising nanofiller for improving the fretting wear performance of UHMWPE. Originality/value The main originality of the research is to reveal the effect of GO and SiO2 nanoparticles on fretting behavior of UHMWPE. The result indicated hybrids of GS were promising nanofiller for improving the fretting wear performance of UHMWPE.

scholarly journals Early-Stage Staphylococcus aureus Bloodstream Infection Causes Changes in the Concentrations of Lipoproteins and Acute-Phase Proteins and Is Associated with Low Antibody Titers against Bacterial Virulence Factors

mSystems ◽  
2020 ◽  
Vol 5 (1) ◽  
Author(s):  
Stephan Michalik ◽  
Nandakumar Sundaramoorthy ◽  
Annette Murr ◽  
Maren Depke ◽  
Uwe Völker ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Bloodstream Infection ◽  
Acute Phase ◽  
Acute Phase Proteins ◽  
High Density Lipoproteins ◽  
Protective Function ◽  
Content Type ◽  
Early Stages ◽  
Serum Igg ◽  
Igg Binding

ABSTRACT Systemic and quantitative investigations of human plasma proteins (proteomics) and Staphylococcus aureus-specific antibodies (immunoproteomics) provide complementary information and hold promise for the discovery of biomarkers in Staphylococcus aureus bloodstream infection (SABSI). Usually, data-dependent acquisition (DDA) is used for proteome analysis of serum or plasma, but data-independent acquisition (DIA) is more comprehensive and reproducible. In this prospective cohort study, we aimed to identify biomarkers associated with the early stages of SABSI using a serum DIA proteomic and immunoproteomic approach. Sera from 49 SABSI patients and 43 noninfected controls were analyzed. In total, 608 human serum proteins were identified with DIA. A total of 386 proteins could be quantified, of which 9 proteins, mainly belonging to acute-phase proteins, were significantly increased, while 7 high-density lipoproteins were lower in SABSI. In SABSI, total anti-S. aureus serum IgG was reduced compared with controls as shown by immunoproteomic quantification of IgG binding to 143 S. aureus antigens. IgG binding to 48 of these anti-S. aureus proteins was significantly lower in SABSI, while anti-Ecb IgG was the only one increased in SABSI. Serum IgG binding to autoinducing peptide MsrB, FadB, EsxA, Pbp2, FadB, SspB, or SodA was very low in SABSI. This marker panel discriminated early SABSI from controls with 95% sensitivity and 100% specificity according to random forest prediction. This holds promise for patient stratification according to their risk of S. aureus infection, underlines the protective function of the adaptive immune system, and encourages further efforts in the development of a vaccine against S. aureus. IMPORTANCE S. aureus sepsis has a high complication and mortality rate. Given the limited therapeutic possibilities, effective prevention strategies, e.g., a vaccine, or the early identification of high-risk patients would be important but are not available. Our study showed an acute-phase response in patients with S. aureus bloodstream infection and evidence that lipoproteins are downregulated in plasma. Using immunoproteomics, stratification of patients appears to be achievable, since at the early stages of systemic S. aureus infection patients had low preexisting anti-S. aureus antibody levels. This strengthens the notion that a robust immune memory for S. aureus protects against infections with the pathogen.

scholarly journals Biofilm and Planktonic Bacterial and Fungal Communities Transforming High-Molecular-Weight Polycyclic Aromatic Hydrocarbons

2016 ◽  
Vol 82 (8) ◽  
pp. 2288-2299 ◽  
Author(s):  
Benjamin D. Folwell ◽  
Terry J. McGenity ◽  
Corinne Whitby
Keyword(s):  
Molecular Weight ◽  
Polycyclic Aromatic Hydrocarbons ◽  
High Molecular Weight ◽  
Community Composition ◽  
Aromatic Hydrocarbons ◽  
Fungal Community ◽  
Bacterial Species ◽  
Bacterial Community Composition ◽  
Content Type ◽  
Polycyclic Aromatic

ABSTRACTHigh-molecular-weight polycyclic aromatic hydrocarbons (HMW-PAHs) are natural components of fossil fuels that are carcinogenic and persistent in the environment, particularly in oil sands process-affected water (OSPW). Their hydrophobicity and tendency to adsorb to organic matter result in low bioavailability and high recalcitrance to degradation. Despite the importance of microbes for environmental remediation, little is known about those involved in HMW-PAH transformations. Here, we investigated the transformation of HMW-PAHs using samples of OSPW and compared the bacterial and fungal community compositions attached to hydrophobic filters and in suspension. It was anticipated that the hydrophobic filters with sorbed HMW-PAHs would select for microbes that specialize in adhesion. Over 33 days, more pyrene was removed (75% ± 11.7%) than the five-ring PAHs benzo[a]pyrene (44% ± 13.6%) and benzo[b]fluoranthene (41% ± 12.6%). For both bacteria and fungi, the addition of PAHs led to a shift in community composition, but thereafter the major factor determining the fungal community composition was whether it was in the planktonic phase or attached to filters. In contrast, the major determinant of the bacterial community composition was the nature of the PAH serving as the carbon source. The main bacteria enriched by HMW-PAHs werePseudomonas,Bacillus, andMicrobacteriumspecies. This report demonstrates that OSPW harbors microbial communities with the capacity to transform HMW-PAHs. Furthermore, the provision of suitable surfaces that encourage PAH sorption and microbial adhesion select for different fungal and bacterial species with the potential for HMW-PAH degradation.

scholarly journals The Succinyl and Acetyl Modifications of Succinoglycan Influence Susceptibility of Succinoglycan to Cleavage by the Rhizobium meliloti Glycanases ExoK and ExsH

1998 ◽  
Vol 180 (16) ◽  
pp. 4184-4191 ◽  
Author(s):  
Gregory M. York ◽  
Graham C. Walker
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Meliloti ◽  
Low Molecular Weight ◽  
Wild Type ◽  
Mutant Strains ◽  
Acetyl Group

ABSTRACT In Rhizobium meliloti (Sinorhizobium meliloti) cultures, the endo-1,3-1,4-β-glycanases ExoK and ExsH depolymerize nascent high-molecular-weight (HMW) succinoglycan to yield low-molecular-weight (LMW) succinoglycan. We report here that the succinyl and acetyl modifications of succinoglycan influence the susceptibility of succinoglycan to cleavage by these glycanases. It was previously shown that exoH mutants, which are blocked in the succinylation of succinoglycan, exhibit a defect in the production of LMW succinoglycan. We have determined that exoZ mutants, which are blocked in the acetylation of succinoglycan, exhibit an increase in production of LMW succinoglycan. For both wild-type andexoZ mutant strains, production of LMW succinoglycan is dependent on the exoK + andexsH + genes, implying that the ExoK and ExsH glycanases cleave HMW succinoglycan to yield LMW succinoglycan. By supplementing cultures of glycanase-deficient strains with exogenously added ExoK or ExsH, we have demonstrated directly that the absence of the acetyl group increases the susceptibility of succinoglycan to cleavage by ExoK and ExsH, that the absence of the succinyl group decreases the susceptibility of succinoglycan to cleavage, and that the succinyl effect outweighs the acetyl effect for succinoglycan lacking both modifications. Strikingly, nonsuccinylated succinoglycan actually can be cleaved by ExoK and ExsH to yield LMW succinoglycan, but only when the glycanases are added to cultures at greater than physiologically relevant concentrations. Thus, we conclude that the molecular weight distribution of succinoglycan in R. meliloti cultures is determined by both the levels of ExoK and ExsH glycanase expression and the susceptibility of succinoglycan to cleavage.

Fretting wear behavior of WS2/ultra-high molecular weight polyethylene nanocomposites

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Xiaocui Xin ◽  
Yunxia Wang ◽  
Zhaojie Meng ◽  
Hao Liu ◽  
Yunfeng Yan ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Peer Review ◽  
High Molecular Weight ◽  
Fretting Wear ◽  
Specific Wear Rate ◽  
Wear Performance ◽  
Content Type ◽  
Ultra High Molecular Weight

Purpose This paper aims to focus on studying the addition of nano-tungsten disulfide (WS2) on fretting wear performance of ultra-high-molecular-weight-polyethylene (UHMWPE). Design/methodology/approach In this study, the effect of WS2 content on fretting wear performance of UHMWPE was investigated. The fretting wear performance of the UHMWPE and WS2/UHMWPE nanocomposites were evaluated on oscillating reciprocating friction and wear tester. The data of the friction coefficient and the specific wear rate were obtained. The worn surfaces of composites were observed. The transfer film and its component were analyzed. Findings With the addition of 0.5% WS2, the friction coefficient and specific wear rate increased. With the content increased to 1% and 1.5%, the friction coefficient and specific wear rate decreased. The lowest friction coefficient and specific wear rate were obtained with the addition of 1.5% nano-WS2. Continuingly increasing content, the friction coefficient and wear rate increased but lower than that of pure UHMWPE. Research limitations/implications The research indicated the fretting wear performance related to the content of nano-WS2 with the incorporation of WS2 into UHMWPE. Practical implications The result may help to choose the appropriate content. Originality/value The main originality of the research is to reveal the fretting behavior of UHMWPE and WS2/UHMWPE nanocomposites. It makes us realize the nano-WS2 had an effect on the fretting wear performance of UHMWPE. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2020-0151/

scholarly journals Activity of Chitosan and Its Derivatives against Leishmania major and Leishmania mexicana In Vitro

2019 ◽  
Vol 64 (3) ◽  
Author(s):  
Alaa Riezk ◽  
John G. Raynes ◽  
Vanessa Yardley ◽  
Sudaxshina Murdan ◽  
Simon L. Croft
Keyword(s):  
Nitric Oxide ◽  
Reactive Oxygen Species ◽  
Molecular Weight ◽  
High Molecular Weight ◽  
Leishmania Major ◽  
Oxygen Species ◽  
Leishmania Mexicana ◽  
Content Type ◽  
High Molecular Weight Chitosan

ABSTRACT There is an urgent need for safe, efficacious, affordable, and field-adapted drugs for the treatment of cutaneous leishmaniasis, which newly affects around 1.5 million people worldwide annually. Chitosan, a biodegradable cationic polysaccharide, has previously been reported to have antimicrobial, antileishmanial, and immunostimulatory activities. We investigated the in vitro activity of chitosan and several of its derivatives and showed that the pH of the culture medium plays a critical role in antileishmanial activity of chitosan against both extracellular promastigotes and intracellular amastigotes of Leishmania major and Leishmania mexicana. Chitosan and its derivatives were approximately 7 to 20 times more active at pH 6.5 than at pH 7.5, with high-molecular-weight chitosan being the most potent. High-molecular-weight chitosan stimulated the production of nitric oxide and reactive oxygen species by uninfected and Leishmania-infected macrophages in a time- and dose-dependent manner at pH 6.5. Despite the in vitro activation of bone marrow macrophages by chitosan to produce nitric oxide and reactive oxygen species, we showed that the antileishmanial activity of chitosan was not mediated by these metabolites. Finally, we showed that rhodamine-labeled chitosan is taken up by pinocytosis and accumulates in the parasitophorous vacuole of Leishmania-infected macrophages.

Unit-cell-based derivation of the material models for armor-grade composites with different architectures of ultra-high molecular-weight polyethylene fibers

2016 ◽  
Vol 7 (4) ◽  
pp. 458-489 ◽  
Author(s):  
Mica Grujicic ◽  
Jennifer Snipes ◽  
S Ramaswami ◽  
Vasudeva Avuthu ◽  
Chian-Fong Yen ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Fiber Reinforcement ◽  
Experimental Investigations ◽  
Transverse Impact ◽  
Ballistic Performance ◽  
Material Models ◽  
Content Type ◽  
Ultra High Molecular Weight ◽  
Polyethylene Fibers

Purpose – Traditionally, an armor-grade composite is based on a two-dimensional (2D) architecture of its fiber reinforcements. However, various experimental investigations have shown that armor-grade composites based on 2D-reinforcement architectures tend to display inferior through-the-thickness mechanical properties, compromising their ballistic performance. To overcome this problem, armor-grade composites based on three-dimensional (3D) fiber-reinforcement architectures have recently been investigated experimentally. The paper aims to discuss these issues. Design/methodology/approach – In the present work, continuum-level material models are derived, parameterized and validated for armor-grade composite materials, having four (two 2D and two 3D) prototypical reinforcement architectures based on oriented ultra-high molecular-weight polyethylene fibers. To properly and accurately account for the effect of the reinforcement architecture, the appropriate unit cells (within which the constituent materials and their morphologies are represented explicitly) are constructed and subjected to a series of virtual mechanical tests (VMTs). The results obtained are used within a post-processing analysis to derive and parameterize the corresponding homogenized-material models. One of these models (specifically, the one for 0°/90° cross-collimated fiber architecture) was directly validated by comparing its predictions with the experimental counterparts. The other models are validated by examining their physical soundness and details of their predictions. Lastly, the models are integrated as user-material subroutines, and linked with a commercial finite-element package, in order to carry out a transient non-linear dynamics analysis of ballistic transverse impact of armor-grade composite-material panels with different reinforcement architectures. Findings – The results obtained clearly revealed the role the reinforcement architecture plays in the overall ballistic limit of the armor panel, as well as in its structural and damage/failure response. Originality/value – To the authors’ knowledge, the present work is the first reported attempt to assess, computationally, the utility and effectiveness of 3D fiber-reinforcement architectures for ballistic-impact applications.

scholarly journals Transcriptome Response to Heavy Metals in Sinorhizobium meliloti CCNWSX0020 Reveals New Metal Resistance Determinants That Also Promote Bioremediation by Medicago lupulina in Metal-Contaminated Soil

2017 ◽  
Vol 83 (20) ◽  
Author(s):  
Mingmei Lu ◽  
Shuo Jiao ◽  
Enting Gao ◽  
Xiuyong Song ◽  
Zhefei Li ◽  
...  
Keyword(s):  
Heavy Metal ◽  
Contaminated Soils ◽  
Sinorhizobium Meliloti ◽  
Heavy Metal Resistance ◽  
Metal Resistance ◽  
Content Type ◽  
Resistance Determinants ◽  
Medicago Lupulina ◽  
Legume Symbiosis ◽  
Cu And Zn

ABSTRACT The symbiosis of the highly metal-resistant Sinorhizobium meliloti CCNWSX0020 and Medicago lupulina has been considered an efficient tool for bioremediation of heavy metal-polluted soils. However, the metal resistance mechanisms of S. meliloti CCNWSX00200 have not been elucidated in detail. Here we employed a comparative transcriptome approach to analyze the defense mechanisms of S. meliloti CCNWSX00200 against Cu or Zn exposure. Six highly upregulated transcripts involved in Cu and Zn resistance were identified through deletion mutagenesis, including genes encoding a multicopper oxidase (CueO), an outer membrane protein (Omp), sulfite oxidoreductases (YedYZ), and three hypothetical proteins (a CusA-like protein, a FixH-like protein, and an unknown protein), and the corresponding mutant strains showed various degrees of sensitivity to multiple metals. The Cu-sensitive mutant (ΔcueO) and three mutants that were both Cu and Zn sensitive (ΔyedYZ, ΔcusA-like, and ΔfixH-like) were selected for further study of the effects of these metal resistance determinants on bioremediation. The results showed that inoculation with the ΔcueO mutant severely inhibited infection establishment and nodulation of M. lupulina under Cu stress, while inoculation with the ΔyedYZ and ΔfixH-like mutants decreased just the early infection frequency and nodulation under Cu and Zn stresses. In contrast, inoculation with the ΔcusA-like mutant almost led to loss of the symbiotic capacity of M. lupulina to even grow in uncontaminated soil. Moreover, the antioxidant enzyme activity and metal accumulation in roots of M. lupulina inoculated with all mutants were lower than those with the wild-type strain. These results suggest that heavy metal resistance determinants may promote bioremediation by directly or indirectly influencing formation of the rhizobium-legume symbiosis. IMPORTANCE Rhizobium-legume symbiosis has been promoted as an appropriate tool for bioremediation of heavy metal-contaminated soils. Considering the plant-growth-promoting traits and survival advantage of metal-resistant rhizobia in contaminated environments, more heavy metal-resistant rhizobia and genetically manipulated strains were investigated. In view of the genetic diversity of metal resistance determinants in rhizobia, their effects on phytoremediation by the rhizobium-legume symbiosis must be different and depend on their specific assigned functions. Our work provides a better understanding of the mechanism of heavy metal resistance determinants involved in the rhizobium-legume symbiosis, and in further studies, genetically modified rhizobia harboring effective heavy metal resistance determinants may be engineered for the practical application of rhizobium-legume symbiosis for bioremediation in metal-contaminated soils.

scholarly journals Draft Genome Sequence of Pseudomonas fragi Strain DBC, Which Has the Ability To Degrade High-Molecular-Weight Polyaromatic Hydrocarbons

2017 ◽  
Vol 5 (49) ◽  
Author(s):  
L. Paikhomba Singha ◽  
Rhitu Kotoky ◽  
Piyush Pandey
Keyword(s):  
Molecular Weight ◽  
Quorum Sensing ◽  
Crude Oil ◽  
High Molecular Weight ◽  
Contaminated Soil ◽  
Polyaromatic Hydrocarbons ◽  
Draft Genome ◽  
Gc Content ◽  
Pseudomonas Fragi ◽  
Content Type

ABSTRACT Pseudomonas fragi strain DBC was isolated from crude oil-contaminated soil. The genome of P. fragi DBC is comprised of 5,072,304 bp with 54.09% GC content. Genes for degradation of polyaromatic hydrocarbons were found in the genome, in addition to genetic elements for related physiological functions such as chemotaxis, detoxification, and quorum sensing.

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