51,529 research outputs found

    Challenges for the development of a biotic ligand model predicting copper toxicity in estuaries and seas

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    This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2011 SETAC.An effort is ongoing to develop a biotic ligand model (BLM) that predicts copper (Cu) toxicity in estuarine and marine environments. At present, the BLM accounts for the effects of water chemistry on Cu speciation, but it does not consider the influence of water chemistry on the physiology of the organisms. We discuss how chemistry affects Cu toxicity not only by controlling its speciation, but also by affecting the osmoregulatory physiology of the organism, which varies according to salinity. In an attempt to understand the mechanisms of Cu toxicity and predict its impacts, we explore the hypothesis that the common factor linking the main toxic effects of Cu is the enzyme carbonic anhydrase (CA), because it is a Cu target with multiple functions and salinity-dependent expression and activity. According to this hypothesis, the site of action of Cu in marine fish may be not only the gill, but also the intestine, because in this tissue CA plays an important role in ion transport and water adsorption. Therefore, the BLM of Cu toxicity to marine fish should also consider the intestine as a biotic ligand. Finally, we underline the need to incorporate the osmotic gradient into the BLM calculations to account for the influence of physiology on Cu toxicity.Brunel Universit

    Identification of a key residue for Oligomerisation and pore-formation of Clostridium perfringens NetB

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    Necrotic enteritis toxin B (NetB) is a β-pore-forming toxin produced by Clostridium perfringens and has been identified as a key virulence factor in the pathogenesis of avian necrotic enteritis, a disease causing significant economic damage to the poultry industry worldwide. In this study, site-directed mutagenesis was used to identify amino acids that play a role in NetB oligomerisation and pore-formation. NetB K41H showed significantly reduced toxicity towards LMH cells and human red blood cells relative to wild type toxin. NetB K41H was unable to oligomerise and form pores in liposomes. These findings suggest that NetB K41H could be developed as a genetic toxoid vaccine to protect against necrotic enteritis

    Small but crucial : the novel small heat shock protein Hsp21 mediates stress adaptation and virulence in Candida albicans

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    Quantitative RNA-seq Analysis Unveils Osmotic and Thermal Adaptation Mechanisms Relevant for Ectoine Production in Chromohalobacter salexigens

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    Quantitative RNA sequencing (RNA-seq) and the complementary phenotypic assays were implemented to investigate the transcriptional responses of Chromohalobacter salexigens to osmotic and heat stress. These conditions trigger the synthesis of ectoine and hydroxyectoine, two compatible solutes of biotechnological interest. Our findings revealed that both stresses make a significant impact on C. salexigens global physiology. Apart from compatible solute metabolism, the most relevant adaptation mechanisms were related to “oxidative- and protein-folding- stress responses,” “modulation of respiratory chain and related components,” and “ion homeostasis.” A general salt-dependent induction of genes related to the metabolism of ectoines, as well as repression of ectoine degradation genes by temperature, was observed. Different oxidative stress response mechanisms, secondary or primary, were induced at low and high salinity, respectively, and repressed by temperature. A higher sensitivity to H2O2 was observed at high salinity, regardless of temperature. Low salinity induced genes involved in “protein-folding-stress response,” suggesting disturbance of protein homeostasis. Transcriptional shift of genes encoding three types of respiratory NADH dehydrogenases, ATP synthase, quinone pool, Na+/H+ antiporters, and sodium-solute symporters, was observed depending on salinity and temperature, suggesting modulation of the components of the respiratory chain and additional systems involved in the generation of H+ and/or Na+ gradients. Remarkably, the Na+ intracellular content remained constant regardless of salinity and temperature. Disturbance of Na+- and H+-gradients with specific ionophores suggested that both gradients influence ectoine production, but with differences depending on the solute, salinity, and temperature conditions. Flagellum genes were strongly induced by salinity, and further induced by temperature. However, salt-induced cell motility was reduced at high temperature, possibly caused by an alteration of Na+ permeability by temperature, as dependence of motility on Na+-gradient was observed. The transcriptional induction of genes related to the synthesis and transport of siderophores correlated with a higher siderophore production and intracellular iron content only at low salinity. An excess of iron increased hydroxyectoine accumulation by 20% at high salinity. Conversely, it reduced the intracellular content of ectoines by 50% at high salinity plus high temperature. These findings support the relevance of iron homeostasis for osmoadaptation, thermoadaptation and accumulation of ectoines, in C. salexigens.España Ministerio de Economía y Competitividad BIO2015-63949-RJunta de Andalucía P11-CVI-729

    Effects of selected insecticides on osmotically treated entomopathogenic nematodes

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    Combining environmentally friendly insecticides with entomopathogenic nematodes may constitute an effective alternative to conventional chemical control of many insect pests. The objective of this laboratory study was to evaluate the effects of selected insecticides which are commonly used for pest control in vegetables in China on osmotically treated and untreated infective juveniles of Steinernema carpocapsae strain All. The insecticides azadirachtin, chlorpyrifos, cypermethrin, fipronil, imidacloprid, malathion, thiamethoxam and chlorantraniliprole-thiamethoxam had no adverse effects on nematode survival and infectivity. In contrast, bisultap, emamectin benzoate, phoxim and rotenone proved harmful to S. carpocapsae All mainly by reducing infectivity of the infective juveniles to larvae of the greater wax moth, Galleria mellonella. Osmotic induction is a promising way to induce entomopathogenic nematodes into partial anhydrobiosis and thus increase environmental stress tolerance of the nematodes as well as their shelf life after production. The present results showed that osmotic treatment did not adversely affect fitness of the nematode in terms of its susceptibility to insecticides and even increased its tolerance to chlorpyrifos and rotenone. The results of this laboratory study indicate that several of the tested insecticides can be safely combined with S. carpocapsae All within an integrated pest management approach

    Hsp90 orchestrates transcriptional regulation by Hsf1 and cell wall remodelling by MAPK signalling during thermal adaptation in a pathogenic yeast

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    Acknowledgments We thank Rebecca Shapiro for creating CaLC1819, CaLC1855 and CaLC1875, Gillian Milne for help with EM, Aaron Mitchell for generously providing the transposon insertion mutant library, Jesus Pla for generously providing the hog1 hst7 mutant, and Cathy Collins for technical assistance.Peer reviewedPublisher PD

    Influence of polar co-solutes and salt on the hydration of lipid membranes

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    The influence of the co-solutes TMAO, urea, and NaCl on the hydration repulsion between lipid membranes is investigated in a combined experimental/simulation approach. Pressure–hydration curves obtained via sorption experiments reveal that the repulsion significantly increases when the membranes are loaded with co-solutes, most strongly for TMAO. As a result, the co-solutes retain additional water molecules and therefore provide membranes with a fluid and more physiological environment. The experimental data are quantitatively reproduced in complementary solvent-explicit atomistic molecular dynamics simulations, which yield the chemical potential of water. Simulation analysis reveals that the additional repulsion arises from the osmotic pressure generated by the co-solutes, an effect which is maximal for TMAO, due to its unfavorable interactions with the lipid headgroup layer and its extraordinarily high osmotic coefficient
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