Artykuły w czasopismach: „ClyA Toxin”

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Sathyanarayana, Pradeep, Satyaghosh Maurya, Amit Behera, Monisha Ravichandran, Sandhya S. Visweswariah, K. Ganapathy Ayappa i Rahul Roy. "Cholesterol promotes Cytolysin A activity by stabilizing the intermediates during pore formation". Proceedings of the National Academy of Sciences 115, nr 31 (16.07.2018): E7323—E7330. http://dx.doi.org/10.1073/pnas.1721228115.

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Pore-forming toxins (PFTs) form nanoscale pores across target membranes causing cell death. Cytolysin A (ClyA) from Escherichia coli is a prototypical α-helical toxin that contributes to cytolytic phenotype of several pathogenic strains. It is produced as a monomer and, upon membrane exposure, undergoes conformational changes and finally oligomerizes to form a dodecameric pore, thereby causing ion imbalance and finally cell death. However, our current understanding of this assembly process is limited to studies in detergents, which do not capture the physicochemical properties of biological membranes. Here, using single-molecule imaging and molecular dynamics simulations, we study the ClyA assembly pathway on phospholipid bilayers. We report that cholesterol stimulates pore formation, not by enhancing initial ClyA binding to the membrane but by selectively stabilizing a protomer-like conformation. This was mediated by specific interactions by cholesterol-interacting residues in the N-terminal helix. Additionally, cholesterol stabilized the oligomeric structure using bridging interactions in the protomer–protomer interfaces, thereby resulting in enhanced ClyA oligomerization. This dual stabilization of distinct intermediates by cholesterol suggests a possible molecular mechanism by which ClyA achieves selective membrane rupture of eukaryotic cell membranes. Topological similarity to eukaryotic membrane proteins suggests evolution of a bacterial α-toxin to adopt eukaryotic motifs for its activation. Broad mechanistic correspondence between pore-forming toxins hints at a wider prevalence of similar protein membrane insertion mechanisms.

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Bräuning, Bastian, i Michael Groll. "Structural and Mechanistic Features of ClyA-Like α-Pore-Forming Toxins". Toxins 10, nr 9 (23.08.2018): 343. http://dx.doi.org/10.3390/toxins10090343.

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Recent technological advances have seen increasing numbers of complex structures from diverse pore-forming toxins (PFT). The ClyA family of α-PFTs comprises a broad variety of assemblies including single-, two- and three-component toxin systems. With crystal structures available for soluble subunits of all major groups in this extended protein family, efforts now focus on obtaining molecular insights into physiological pore formation. This review provides an up-to-date discussion on common and divergent structural and functional traits that distinguish the various ClyA family PFTs. Open questions of this research topic are outlined and discussed.

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Murase, Kazunori. "Cytolysin A (ClyA): A Bacterial Virulence Factor with Potential Applications in Nanopore Technology, Vaccine Development, and Tumor Therapy". Toxins 14, nr 2 (21.01.2022): 78. http://dx.doi.org/10.3390/toxins14020078.

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Cytolysin A (ClyA) is a pore-forming toxin that is produced by some bacteria from the Enterobacteriaceae family. This review provides an overview of the current state of knowledge regarding ClyA, including the prevalence of the encoding gene and its transcriptional regulation, the secretion pathway used by the protein, and the mechanism of protein assembly, and highlights potential applications of ClyA in biotechnology. ClyA expression is regulated at the transcriptional level, primarily in response to environmental stressors, and ClyA can exist stably both as a soluble monomer and as an oligomeric membrane complex. At high concentrations, ClyA induces cytolysis, whereas at low concentrations ClyA can affect intracellular signaling. ClyA is secreted in outer membrane vesicles (OMVs), which has important implications for biotechnology applications. For example, the native pore-forming ability of ClyA suggests that it could be used as a component of nanopore-based technologies, such as sequencing platforms. ClyA has also been exploited in vaccine development owing to its ability to present antigens on the OMV surface and provoke a robust immune response. In addition, ClyA alone or OMVs carrying ClyA fusion proteins have been investigated for their potential use as anti-tumor agents.

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Roderer, Daniel, i Rudi Glockshuber. "Assembly mechanism of the α-pore–forming toxin cytolysin A from Escherichia coli". Philosophical Transactions of the Royal Society B: Biological Sciences 372, nr 1726 (19.06.2017): 20160211. http://dx.doi.org/10.1098/rstb.2016.0211.

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The cytolytic toxin cytolysin A (ClyA) from Escherichia coli is probably one of the best-characterized examples of bacterial, α-pore–forming toxins (α-PFTs). Like other PFTs, ClyA exists in a soluble, monomeric form that assembles to an annular, homo-oligomeric pore complex upon contact with detergent or target membranes. Comparison of the three-dimensional structures of the 34 kDa monomer and the protomer in the context of the dodecameric pore complex revealed that ClyA undergoes one of the largest conformational transitions described for proteins so far, in which 55% of the residues change their position and 16% of the residues adopt a different secondary structure in the protomer. Studies on the assembly of ClyA revealed a unique mechanism that differs from the assembly mechanism of other PFTs. The rate-liming step of pore formation proved to be the unimolecular conversion of the monomer to an assembly-competent protomer, during which a molten globule-like off-pathway intermediate accumulates. The oligomerization of protomers to pore complexes is fast and follows a kinetic scheme in which mixtures of linear oligomers of different size are formed first, followed by very rapid and specific association of pairs of oligomers that can directly perform ring closure to the dodecameric pore complex. This article is part of the themed issue ‘Membrane pores: from structure and assembly, to medicine and technology’.

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Ludwig, Albrecht, Christine von Rhein, Susanne Bauer, Christian Hüttinger i Werner Goebel. "Molecular Analysis of Cytolysin A (ClyA) in Pathogenic Escherichia coli Strains". Journal of Bacteriology 186, nr 16 (15.08.2004): 5311–20. http://dx.doi.org/10.1128/jb.186.16.5311-5320.2004.

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ABSTRACT Cytolysin A (ClyA) of Escherichia coli is a pore-forming hemolytic protein encoded by the clyA (hlyE, sheA) gene that was first identified in E. coli K-12. In this study we examined various clinical E. coli isolates with regard to the presence and integrity of clyA. PCR and DNA sequence analyses demonstrated that 19 of 23 tested Shiga toxin-producing E. coli (STEC) strains, all 7 tested enteroinvasive E. coli (EIEC) strains, 6 of 8 enteroaggregative E. coli (EAEC) strains, and 4 of 7 tested enterotoxigenic E. coli (ETEC) strains possess a complete clyA gene. The remaining STEC, EAEC, and ETEC strains and 9 of the 17 tested enteropathogenic E. coli (EPEC) strains were shown to harbor mutant clyA derivatives containing 1-bp frameshift mutations that cause premature termination of the coding sequence. The other eight EPEC strains and all tested uropathogenic and new-born meningitis-associated E. coli strains (n = 14 and 3, respectively) carried only nonfunctional clyA fragments due to the deletion of two sequences of 493 bp and 204 or 217 bp at the clyA locus. Expression of clyA from clinical E. coli isolates proved to be positively controlled by the transcriptional regulator SlyA. Several tested E. coli strains harboring a functional clyA gene produced basal amounts of ClyA when grown under standard laboratory conditions, but most of them showed a clyA-dependent hemolytic phenotype only when SlyA was overexpressed. The presented data indicate that cytolysin A can play a role only for some of the pathogenic E. coli strains.

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Ludwig, Albrecht, Guido Völkerink, Christine von Rhein, Susanne Bauer, Elke Maier, Birgit Bergmann, Werner Goebel i Roland Benz. "Mutations Affecting Export and Activity of Cytolysin A from Escherichia coli". Journal of Bacteriology 192, nr 15 (28.05.2010): 4001–11. http://dx.doi.org/10.1128/jb.01283-09.

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ABSTRACT Cytolysin A (known as ClyA, HlyE, and SheA) is a cytolytic pore-forming protein toxin found in several Escherichia coli and Salmonella enterica strains. The structure of its water-soluble monomeric form and that of dodecameric ClyA pores is known, but the mechanisms of ClyA export from bacterial cells and of pore assembly are only partially understood. Here we used site-directed mutagenesis to study the importance of different regions of the E. coli ClyA protein for export and activity. The data indicate that ClyA translocation to the periplasm requires several protein segments located closely adjacent to each other in the “tail” domain of the ClyA monomer, namely, the N- and C-terminal regions and the hydrophobic sequence ranging from residues 89 to 101. Deletion of most of the “head” domain of the monomer (residues 181 to 203), on the other hand, did not strongly affect ClyA secretion, suggesting that the tail domain plays a particular role in export. Furthermore, we found that the N-terminal amphipathic helix αA1 of ClyA is crucial for the formation and the properties of the transmembrane channel, and hence for hemolytic activity. Several mutations affecting the C-terminal helix αG, the “β-tongue” region in the head domain, or the hydrophobic region in the tail domain of the ClyA monomer strongly impaired the hemolytic activity and reduced the activity toward planar lipid bilayer membranes but did not totally prevent formation of wild-type-like channels in these artificial membranes. The latter regions thus apparently promote membrane interaction without being directly required for pore formation in a lipid bilayer.

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von Rhein, Christine, Klaus-Peter Hunfeld i Albrecht Ludwig. "Serologic Evidence for Effective Production of Cytolysin A in Salmonella enterica Serovars Typhi and Paratyphi A during Human Infection". Infection and Immunity 74, nr 11 (21.08.2006): 6505–8. http://dx.doi.org/10.1128/iai.00779-06.

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ABSTRACT ClyASTy and ClyASPaA are closely related pore-forming cytolysins of Salmonella enterica serovars Typhi and Paratyphi A whose expression is strongly repressed under standard in vitro growth conditions. We show here that human infections by these pathogens cause a specific antibody response to ClyA, indicating effective toxin production during infection.

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Vaidyanathan, M. S., Pradeep Sathyanarayana, Prabal K. Maiti, Sandhya S. Visweswariah i K. G. Ayappa. "Lysis dynamics and membrane oligomerization pathways for Cytolysin A (ClyA) pore-forming toxin". RSC Advances 4, nr 10 (2014): 4930. http://dx.doi.org/10.1039/c3ra45159c.

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Dingfelder, Fabian, Stephan Benke, Daniel Nettels i Benjamin Schuler. "Mapping an Equilibrium Folding Intermediate of the Cytolytic Pore Toxin ClyA with Single-Molecule FRET". Journal of Physical Chemistry B 122, nr 49 (29.08.2018): 11251–61. http://dx.doi.org/10.1021/acs.jpcb.8b07026.

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Huang, Jinbo, Zeyuan Guan, Liting Wan, Tingting Zou i Ming Sun. "Crystal structure of Cry6Aa: A novel nematicidal ClyA-type α-pore-forming toxin from Bacillus thuringiensis". Biochemical and Biophysical Research Communications 478, nr 1 (wrzesień 2016): 307–13. http://dx.doi.org/10.1016/j.bbrc.2016.07.002.

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Highet, Amanda R., Anne M. Berry, Karl A. Bettelheim i Paul N. Goldwater. "The frequency of molecular detection of virulence genes encoding cytolysin A, high-pathogenicity island and cytolethal distending toxin of Escherichia coli in cases of sudden infant death syndrome does not differ from that in other infant deaths and healthy infants". Journal of Medical Microbiology 58, nr 3 (1.03.2009): 285–89. http://dx.doi.org/10.1099/jmm.0.005322-0.

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Consistent pathological findings in sudden infant death syndrome (SIDS) are seen which display similarities to the pathogenesis of toxaemic shock and/or sepsis. A key candidate infectious agent that is possibly involved is Escherichia coli, given its universal early colonization of the intestinal tract of infants and an increased frequency of toxigenic and mouse-lethal isolates from SIDS compared with comparison infants. An explanation for these findings has yet to be identified. Using PCR, we screened E. coli isolates from 145 SIDS and 101 dead control and healthy infants for three new candidate pathogenicity-related genes: clyA (cytolysin A), irp2 [high-pathogenicity island (HPI)-specific gene] and cdt (cytolethal distending toxin). The results failed to show a positive correlation with SIDS, instead proving that clyA and irp2 genes were common to the infant intestinal E. coli. Interestingly we observed a high rate of carriage of these two potentially pathogenic genes in E. coli from healthy infants in the absence of diarrhoeal disease, and we report that in a number of cases, the detection of HPI-specific genes was predictable by serotype. Despite the lack of associations defined so far, there remains the likelihood that genetic determinants influence the interactions between E. coli and the host, so these factors may be part of the multi-factorial aspect of SIDS.

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Roderer, Daniel, Stephan Benke, Marcus Müller, Helene Fäh-Rechsteiner, Nenad Ban, Benjamin Schuler i Rudi Glockshuber. "Characterization of Variants of the Pore-Forming Toxin ClyA from Escherichia coli Controlled by a Redox Switch". Biochemistry 53, nr 40 (30.09.2014): 6357–69. http://dx.doi.org/10.1021/bi5007578.

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Galen, James E., Jin Yuan Wang, Magaly Chinchilla, Christopher Vindurampulle, Jeffrey E. Vogel, Haim Levy, William C. Blackwelder, Marcela F. Pasetti i Myron M. Levine. "A New Generation of Stable, Nonantibiotic, Low-Copy-Number Plasmids Improves Immune Responses to Foreign Antigens in Salmonella enterica Serovar Typhi Live Vectors". Infection and Immunity 78, nr 1 (2.11.2009): 337–47. http://dx.doi.org/10.1128/iai.00916-09.

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ABSTRACTWe hypothesized that adequately engineered attenuatedSalmonella entericaserovar Typhi strains can serve as multivalent mucosal live vector vaccines to immunize against unrelated human pathogens. Toward this ultimate goal, we have developed a novel genetic stabilization system for antigen-expressing plasmids, engineered to encode the single-stranded binding protein (SSB), an essential protein involved in DNA metabolism which was deleted from the live vector chromosome. We utilized full-length protective antigen (PA83) of anthrax toxin fromBacillus anthracisas a foreign antigen and expressed PA83 as a fusion with the ClyA export protein, which allows export of ClyA-PA83 to the surface ofS. Typhi live vectors. A series of SSB-encoding multicopy expression plasmids were introduced into reengineeredS. Typhi strains previously tested in clinical trials, i.e., CVD 908-htrAand its less attenuated parent CVD 908. Immunogenicity was examined using a mouse model of intranasal immunization with live vector, followed by parenteral boosting with purified PA83. PA-specific antibody responses markedly improved as the copy number of the SSB-encoding plasmids decreased, and this effect was dramatically enhanced when the foreign antigen was delivered by the less attenuated live vector CVD 908ssb. These results suggest that antibody responses to antigens delivered byS. Typhi live vectors are inversely related to the metabolic burden imposed by expression of the foreign antigen and that these responses can be improved when antigens are expressed from low-copy-number plasmids and exported out of the cytoplasm of less attenuated live vectors.

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Wyborn, Neil R., Melanie R. Stapleton, Valia A. Norte, Ruth E. Roberts, Jamie Grafton i Jeffrey Green. "Regulation of Escherichia coli Hemolysin E Expression by H-NS and Salmonella SlyA". Journal of Bacteriology 186, nr 6 (15.03.2004): 1620–28. http://dx.doi.org/10.1128/jb.186.6.1620-1628.2004.

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ABSTRACT The Escherichia coli hlyE gene (also known as clyA or sheA) codes for a novel pore-forming toxin. Previous work has shown that the global transcription factors FNR and CRP positively regulate hlyE expression by binding at the same site. Here in vivo transcription studies reveal that FNR occupies the hlyE promoter more frequently than CRP, providing a mechanism for the moderate upregulation of hlyE expression in response to two distinct environmental signals (oxygen and glucose starvation). It has been reported that H-NS interacts with two large regions of the hlyE promoter (PhlyE), one upstream of the −35 element and one downstream of the −10 element. Here we identify two high-affinity H-NS sites, H-NS I, located at the 3′ end of the extended upstream footprint, and H-NS II, located at the 5′ end of the extended downstream footprint. It is suggested that these high-affinity sites initiate the progressive formation of higher order complexes, allowing a range of H-NS-mediated regulatory effects at PhlyE. Finally, the identification of a SlyA binding site that overlaps the H-NS I site in PhlyE suggests a mechanism to explain how SlyA overproduction enhances hlyE expression by antagonizing the negative effects of H-NS.

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Sannigrahi, Achinta, Vishwesh Haricharan Rai, Muhsin Vannan Chalil, Debayani Chakraborty, Subrat Kumar Meher i Rahul Roy. "A Versatile Suspended Lipid Membrane System for Probing Membrane Remodeling and Disruption". Membranes 12, nr 12 (25.11.2022): 1190. http://dx.doi.org/10.3390/membranes12121190.

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Artificial membrane systems can serve as models to investigate molecular mechanisms of different cellular processes, including transport, pore formation, and viral fusion. However, the current, such as SUVs, GUVs, and the supported lipid bilayers suffer from issues, namely high curvature, heterogeneity, and surface artefacts, respectively. Freestanding membranes provide a facile solution to these issues, but current systems developed by various groups use silicon or aluminum oxide wafers for fabrication that involves access to a dedicated nanolithography facility and high cost while conferring poor membrane stability. Here, we report the development, characterization and applications of an easy-to-fabricate suspended lipid bilayer (SULB) membrane platform leveraging commercial track-etched porous filters (PCTE) with defined microwell size. Our SULB system offers a platform to study the lipid composition-dependent structural and functional properties of membranes with exceptional stability. With dye entrapped in PCTE microwells by SULB, we show that sphingomyelin significantly augments the activity of pore-forming toxin, Cytolysin A (ClyA) and the pore formation induces lipid exchange between the bilayer leaflets. Further, we demonstrate high efficiency and rapid kinetics of membrane fusion by dengue virus in our SULB platform. Our suspended bilayer membrane mimetic offers a novel platform to investigate a large class of biomembrane interactions and processes.

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Fagerlund, Annette, Toril Lindbäck, Anne K. Storset, Per Einar Granum i Simon P. Hardy. "Bacillus cereus Nhe is a pore-forming toxin with structural and functional properties similar to the ClyA (HlyE, SheA) family of haemolysins, able to induce osmotic lysis in epithelia". Microbiology 154, nr 5 (1.05.2008): 1554. http://dx.doi.org/10.1099/mic.0.29847-0.

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Fagerlund, Annette, Toril Lindbäck, Anne K. Storset, Per Einar Granum i Simon P. Hardy. "Bacillus cereus Nhe is a pore-forming toxin with structural and functional properties similar to the ClyA (HlyE, SheA) family of haemolysins, able to induce osmotic lysis in epithelia". Microbiology 154, nr 3 (1.03.2008): 693–704. http://dx.doi.org/10.1099/mic.0.2007/014134-0.

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Leung, D. Y., M. Gately, A. Trumble, B. Ferguson-Darnell, P. M. Schlievert i L. J. Picker. "Bacterial superantigens induce T cell expression of the skin-selective homing receptor, the cutaneous lymphocyte-associated antigen, via stimulation of interleukin 12 production." Journal of Experimental Medicine 181, nr 2 (1.02.1995): 747–53. http://dx.doi.org/10.1084/jem.181.2.747.

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T lymphocyte infiltration is a prominent feature of the skin inflammation associated with infections by toxin (superantigen)-secreting Staphylococcus aureus or Streptococcus bacteria. The cutaneous lymphocyte-associated antigen (CLA) has been hypothesized to be a homing receptor (HR) involved in selective migration of memory/effector T cells to the skin. Since the expression of this putative skin-selective HR is known to be under strict microenvironmental control, we sought to determine the effect of staphylococcal and streptococcal toxins on T cell expression of CLA. After in vitro stimulation of peripheral blood mononuclear cells with staphylococcal enterotoxin B, toxic shock syndrome toxin-1, and streptococcal pyrogenic exotoxins A and C, there was a significant increase in the numbers of CLA+ T cell blasts (p < 0.01), but not blasts bearing the mucosa-associated adhesion molecule alpha e beta 7-integrin, compared with T cells stimulated with phytohemaglutinin (PHA) or anti-CD3. Bacterial toxins were also found to specifically induce interleukin (IL) 12 production. More importantly, induction of toxin-induced CLA expression was blocked by anti-IL-12, and the addition of IL-12 to PHA-stimulated T cells induced CLA, but not alpha e beta 7-integrin, expression. These data suggest that bacterial toxins induce the expansion of skin-homing CLA+ T cells in an IL-12-dependent manner, and thus may contribute to the development of skin rashes in superantigen-mediated diseases.

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Tapp, H., i G. Stotzky. "Monitoring the insecticidal toxins fromBacillus thuringiensisin soil with flow cytometry". Canadian Journal of Microbiology 43, nr 11 (1.11.1997): 1074–78. http://dx.doi.org/10.1139/m97-153.

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The accumulation and persistance in soil and other natural habitats of the insecticidal toxins from Bacillus thuringiensis may result in environmental hazards, such as toxicity to nontarget species and the selection of toxin-resistant target species. We describe the use of flow cytometry as a method for detecting and tracking the fate of these insecticidal toxins in soil that does not require their extraction and purification. The toxins from B. thuringiensis subspp. tenebrionis and kurstaki were bound on clay- or silt-sized particles separated from Kitchawan soil that was unamended (naturally contains predominantly kaolinite) or amended to 6% v/v with the clay minerals montmorillonite or kaolinite (as an internal control). The particle–toxin mixtures were suspended in 0.1 M phosphate buffer (pH 7) containing 3% nonfat milk powder to block nonspecific binding of antibody, resuspended in a solution of antibody to the toxin from B. thuringiensis subsp. tenebrionis, and then resuspended in a solution of anti-rabbit antibody conjugated with fluorescein isothiocyanate (FITC–Ab). Controls consisted of the particles alone and bound complexes of the particles with the toxin from B. thuringiensis subsp. kurstaki. All particles that bound the toxin from B. thuringiensis subsp. tenebrionis showed a significant shift in the peak of fluorescence to the right on the x axis as compared with the nonspecific fluorescence from the control FITC–Ab complexes with particles in the absence of the toxin. There was also a slight shift in the peak to the right for some particles that bound the toxin from B. thuringiensis subsp. tenebrionis, as there is some cross-reactivity between the toxins from B. thuringiensis subspp. tenebrionis and kurstaki and the antibodies that they induce. This method is more sensitive and rapid than the dot-blot ELISA, and processing of many samples is easily accomplished.Key words: flow cytometry, soil, insecticidal toxins, Bacillus thuringiensis, clay, silt.

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Miller, M. J., i H. J. Fallowfield. "Degradation of cyanobacterial hepatotoxins in batch experiments". Water Science and Technology 43, nr 12 (1.06.2001): 229–32. http://dx.doi.org/10.2166/wst.2001.0745.

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Bank filtration offers a cost effective and low maintenance technique for the removal of cyanobacterial hepatotoxins from drinking water. For bank filtration to be effective, the toxins must be degraded. The broad aim of this research was to determine whether the hepatotoxins, nodularin and microcystin-LR, could be completely removed from the soil/water matrix of three soils by microbial degradation. The results indicated that complete toxin removal was possible within 10-16 d in 2/3 soils that were incubated in the dark at 20°C. The soils with the highest organic carbon content (2.9%) and the highest clay content (16.1%) were the most effective at removing the toxins in batch experiments. However, the sandy soil (98.5% sand) was incapable of degrading either toxin. The half-lives of toxin losses due to adsorption, desorption and degradation were calculated and for all soils. The degradation process had the highest half-life for both toxins. This suggested that degradation was likely to be the rate-limiting step of complete toxin removal. It was concluded that when a bank filtration site was being chosen, the degradation potential and the textural properties of the riverbank soil would be important when considering complete removal of cyanobacterial hepatotoxins.

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Waryah, Charlene Babra, Jully Gogoi-Tiwari, Kelsi Wells, Karina Yui Eto, Elnaz Masoumi, Paul Costantino, Michael Kotiw i Trilochan Mukkur. "Diversity of Virulence Factors Associated with West Australian Methicillin-SensitiveStaphylococcus aureusIsolates of Human Origin". BioMed Research International 2016 (2016): 1–10. http://dx.doi.org/10.1155/2016/8651918.

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An extensive array of virulence factors associated withS. aureushas contributed significantly to its success as a major nosocomial pathogen in hospitals and community causing variety of infections in affected patients. Virulence factors include immune evading capsular polysaccharides, poly-N-acetyl glucosamine, and teichoic acid in addition to damaging toxins including hemolytic toxins, enterotoxins, cytotoxins, exfoliative toxin, and microbial surface components recognizing adhesive matrix molecules (MSCRAMM). In this investigation, 31 West AustralianS. aureusisolates of human origin and 6 controls were analyzed for relative distribution of virulence-associated genes using PCR and/or an immunoassay kit and MSCRAMM by PCR-based typing. Genes encoding MSCRAMM, namely, Spa, ClfA, ClfB, SdrE, SdrD, IsdA, and IsdB, were detected in >90% of isolates. Gene encodingα-toxin was detected in >90% of isolates whereas genes encodingβ-toxin and SEG were detectable in 50–60% of isolates. Genes encoding toxin proteins, namely, SEA, SEB, SEC, SED, SEE, SEH, SEI, SEJ, TSST, PVL, ETA, and ETB, were detectable in >50% of isolates. Use of RAPD-PCR for determining the virulence factor-based genetic relatedness among the isolates revealed five cluster groups confirming genetic diversity among the MSSA isolates, with the greatest majority of the clinicalS. aureus(84%) isolates clustering in group IIIa.

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Jaynes, William F., Richard E. Zartman, Cary J. Green, Michael J. San Francisco i John C. Zak. "Castor toxin adsorption to clay minerals". clays and clay minerals 53, nr 3 (1.06.2005): 268–77. http://dx.doi.org/10.1346/ccmn.2005.0530306.

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Akbar, Saba. "Efficacy of clay minerals for controlling aflatoxin B1 toxicity in commercial broilers". Pakistan Journal of Agricultural Sciences 59, nr 02 (1.03.2022): 231–39. http://dx.doi.org/10.21162/pakjas/22.1060.

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Aflatoxin occurrence in poultry feed causes aflatoxicosis in birds and poses health hazards to the consumers. Aflatoxin B1 (AfB1) is the most predominant and toxic metabolite that is controlled through addition of argillaceous clays as non-nutritive additives. Non-smectitic indigenous clay reserves need testing as AfB1 adsorbent. With detailed mineral and adsorption characteristics, three indigenous non-smectitic clays: (i) palygorskite, (ii) palygorskite-smectite mix, and (iii) interstratified smectite with hydroxy interlayered smectite were tested against 250 µg kg-1 AfB1 contamination in a poultry feeding trial with three replications at 1% and 2% (w/w) with positive and negative controls. A total of 330 Ross-308 male broiler chicks, initially reared on clean feed under controlled conditions of light and humidity, were distributed into eleven treatment combinations in a completely randomized design with 30 birds in each treatment on an equal weight basis with three replications at day 14 and fed on experimental feeds for three weeks. Three birds from each pen were randomly slaughtered at day 35 and for each replicated treatment, body weight gain, feed intake, and internal organs weight and morphology were recorded. AfB1 contamination reduced weight gain (p 0.0001), feed conversion ratio (p 0.0001) and feed intake (p 0.0001) while clays addition in the toxin feed effectively controlled AfB1 toxicity as suggested by improved body weight, weight gain rate and feed consumption compared to the toxin fed birds. The liver morphology was comparatively better in palygorskite-smectite mix treatment when applied at 1% and the darkish colour was also improved with addition of the clay in the toxin feed. AfB1 feeding caused a 75% reduction in weight gain compared to the clean feed. Palygorskite and palygorskite-smectite mix clays were better than interstratified clay in increasing weight gain and caused a 60% and 65% increase over toxin feed treatment when applied at 1% and 2%, respectively. In conclusion, the indigenous clay sources overall and palygorskite-smectite mix in particular has the potential for use as a mycotoxin binder for controlling AfB1 incidence in poultry

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Lee, LanNa, Deepak Saxena i G. Stotzky. "Activity of Free and Clay-Bound Insecticidal Proteins from Bacillus thuringiensis subsp. israelensis against the Mosquito Culex pipiens". Applied and Environmental Microbiology 69, nr 7 (lipiec 2003): 4111–15. http://dx.doi.org/10.1128/aem.69.7.4111-4115.2003.

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ABSTRACT Bacillus thuringiensis subsp. israelensis produces parasporal insecticidal crystal proteins (ICPs) that have larvicidal activity against some members of the order Diptera, such as blackflies and mosquitoes. Hydrolysis of the ICPs in the larval gut results in four major proteins with a molecular mass of 27, 65, 128, and 135 kDa. Toxicity is caused by synergistic interaction between the 25-kDa protein (proteolytic product of the 27-kDa protein) and one or more of the higher-molecular-mass proteins. Equilibrium adsorption of the proteins on the clay minerals montmorillonite and kaolinite, which are homoionic to various cations, was rapid (<30 min for maximal adsorption), increased with protein concentration and then reached a plateau (68 to 96% of the proteins was adsorbed), was significantly lower on kaolinite than on montmorillonite, and was not significantly affected by the valence of the cation to which the clays were homoionic. Binding of the toxins decreased as the pH was increased from 6 to 11, and there was 35 to 66% more binding in phosphate buffer at pH 6 than in distilled water at pH 6 or 7.2. Only 2 to 12% of the adsorbed proteins was desorbed by two washes with water; additional washings desorbed no more toxins, indicating that they were tightly bound. Formation of clay-toxin complexes did not alter the structure of the proteins, as indicated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the equilibrium supernatants and desorption washes and by dot blot enzyme-linked immunosorbent assay of the complexes, which was confirmed by enhanced chemiluminescence Western blot analysis. Free and clay-bound toxins resulted in 85 to 100% mortality of the mosquito Culex pipiens. Persistence of the bound toxins in nonsterile water after 45 days was significantly greater (mortality of 63% ± 12.7%) than that of the free toxins (mortality of 25% ± 12.5%).

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Olopade, Bunmi K., Solomon U. Oranusi, Obinna C. Nwinyi, Isiaka A. Lawal, Sefater Gbashi i Patrick B. Njobeh. "Decontamination of T-2 Toxin in Maize by Modified Montmorillonite Clay". Toxins 11, nr 11 (24.10.2019): 616. http://dx.doi.org/10.3390/toxins11110616.

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Montmorillonite clay has a wide range of applications, one of which includes the binding of mycotoxins in foods and feeds through adsorption. T-2 toxin, produced by some Fusarium, Myrothecium, and Stachybotrys species, causes dystrophy in the brain, heart, and kidney. Various formulations that include lemongrass essential oil-modified montmorillonite clay (LGEO-MMT), lemongrass powder (LGP), montmorillonite clay washed with 1 mM NaCl (Na-MMT), montmorillonite clay (MMT), and lemongrass powder mixed with montmorillonite clay (LGP-MMT) were applied to maize at concentrations of 8% and 12% and stored for a period of one month at 30 °C. Unmodified montmorillonite clay and LGP served as the negative controls alongside untreated maize. Fourier Transform Infrared (FTIR) spectra of the various treatments showed the major functional groups as Si-O and -OH. All treatment formulations were effective in the decontamination of T-2 toxin in maize. Accordingly, it was revealed that the inclusion of Na-MMT in maize at a concentration of 8% was most effective in decontaminating T-2 toxin by 66% in maize followed by LGP-MMT at 12% inclusion level recording a 56% decontamination of T-2 toxin in maize (p = 0.05). Montmorillonite clay can be effectively modified with plant extracts for the decontamination of T-2 toxin.

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Vejvodova, Katerina, Ondřej Drábek, Christopher Ash, Václav Tejnecký, Karel Němeček i Luboš Borůvka. "Effect of clay on the fractions of potentially toxic elements in contaminated soil". Soil and Water Research 16, No. 1 (11.12.2020): 1–10. http://dx.doi.org/10.17221/13/2020-swr.

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The aim of the study was to evaluate the effect of clay as an amendment to decrease the mobility and plant availability of potentially toxic elements (PTEs). Kaolinite and vermiculite were added at a 9% application rate to a contaminated garden soil from Kutná Hora. Half of the original soil was acidified by the addition of HNO<sub>3</sub>, to observe the effect of the pH on the adsorption of the PTEs. The samples were analysed four times over an eight-week period to evaluate the effect of the clay additions on the As, Cd, Pb and Zn plant availability and different fractions of the BCR sequential extraction. The results indicate that the PTEs were mainly bound by ion/cation exchange on the edges of the clay minerals and onto the Fe/Mn oxides and organic fractions in the soils. The significance (P < 0.05) of the pH was observed for the plant availability of the PTE, especially on the As and Cd. A comparison of the vermiculite in the form of chunks and as powder displayed the most statistically significant results, where the vermiculite powder significantly decreased the plant availability of the As, Cd and Pb, while the opposite effect was observed for the Zn.

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Miller, Megge J., John Hutson i Howard J. Fallowfield. "The adsorption of cyanobacterial hepatoxins as a function of soil properties". Journal of Water and Health 3, nr 4 (1.12.2005): 339–47. http://dx.doi.org/10.2166/wh.2005.049.

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Cyanobacterial hepatotoxins present a risk to public health when present in drinking water supplies. Existing removal strategies, although efficient, are not economically viable or practical for remote Australian communities and developing nations. Bank filtration is a natural process and a potential low cost, toxin removal strategy. Batch studies were conducted in 12 texturally diverse soils to examine the soil properties influencing the adsorption of the cyanobacterial hepatotoxins, microcystin-LR and nodularin. Sorption isotherms were measured. Freundlich and linear isotherms were observed for both toxins with adsorption coefficients not exceeding 2.75 l kg−1 for nodularin and 3.8 l kg−1 for microcystin. Significant positive correlations were identified between hepatotoxin sorption and clay and silt contents of the soils. Desorption of toxins was also measured in three different soils. Pure nodularin and microcystin-LR readily desorbed from all soils.

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Kim, Eun Jin, Hyun Jin Yu, Je Hee Lee, Jae-Ouk Kim, Seung Hyun Han, Cheol-Heui Yun, Jongsik Chun, G. Balakrish Nair i Dong Wook Kim. "Replication ofVibrio choleraeclassical CTX phage". Proceedings of the National Academy of Sciences 114, nr 9 (14.02.2017): 2343–48. http://dx.doi.org/10.1073/pnas.1701335114.

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The toxigenic classical and El Tor biotypeVibrio choleraeserogroup O1 strains are generated by lysogenization of host-type–specific cholera toxin phages (CTX phages). Experimental evidence of the replication and transmission of an El Tor biotype-specific CTX phage, CTX-1, has explained the evolution ofV. choleraeEl Tor biotype strains. The generation of classical biotype strains has not been demonstrated in the laboratory, and the classical biotype-specific CTX phage, CTX-cla, is considered to be defective with regard to replication. However, the identification of atypical El Tor strains that contain CTX-cla–like phage, CTX-2, indicates that CTX-cla and CTX-2 replicate and can be transmitted toV. choleraestrains. The replication of CTX-cla and CTX-2 phages and the transduction of El Tor biotype strains by various CTX phages under laboratory conditions are demonstrated in this report. We have established a plasmid-based CTX phage replication system that supports the replication of CTX-1, CTX-cla, CTX-2, and CTX-O139. The replication of CTX-2 from the tandem repeat of lysogenic CTX-2 in Wave 2 El Tor strains is also presented. El Tor biotype strains can be transduced by CTX phages in vitro by introducing a point mutation intoxT, the transcriptional activator of thetcp(toxin coregulated pilus) gene cluster and the cholera toxin gene. This mutation also increases the expression of cholera toxin in El Tor strains in a sample single-phase culture. Our results thus constitute experimental evidence of the genetic mechanism of the evolution ofV. cholerae.

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Zhou, X. Y., H. F. Liu, X. Z. Lu, J. C. Hao, L. L. Shi i Q. Hu. "Effect of Zn on the adsorption and desorption of Cry1Ab toxin from Bacillus thuringiensis on clay minerals". Clay Minerals 48, nr 4 (wrzesień 2013): 605–12. http://dx.doi.org/10.1180/claymin.2013.048.4.04.

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AbstractThe influence of Zn on the adsorption and desorption of Cry1Ab toxin from Bacillus thuringiensis (Bt) on palygorskite and montmorillonite was studied. The adsorption of the toxin gradually increased with increasing Zn concentration from 0 to 1.0 mmol L–1, and then decreased with further increase in Zn concentration. The adsorption isotherms of the toxin in the absence and presence of Zn were well described by the Langmuir equation (R2 > 0.9810–0.9991). The separation factor (RL) decreased with increase of Zn concentration, suggesting that the irreversibility of the adsorption increases. The XRD results showed that the treatment by Tris buffer or Zn(NO3)2 solution caused an expansion of the interlayer space of montmorillonite but did not affect palygorskite. The IR spectra suggest that Zn was likely to be combined with amino groups on the surface of the toxin. The presence of Zn during the adsorption of the toxin decreased desorption, suggesting that the residual risk of toxin would be exacerbated if soil is polluted by zinc.

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Alabdullah, Hussain A., Elise Overgaard, Danielle Scarbrough, Janet E. Williams, Omid Mohammad Mousa, Gary Dunn, Laura Bond, Mark A. McGuire i Juliette K. Tinker. "Evaluation of the Efficacy of a Cholera Toxin-Based Staphylococcus aureus Vaccine against Bovine Intramammary Challenge". Vaccines 9, nr 1 (24.12.2020): 6. http://dx.doi.org/10.3390/vaccines9010006.

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Staphylococcus aureus (S. aureus) is a primary agent of bovine mastitis and a source of significant economic loss for the dairy industry. We previously reported antigen-specific immune induction in the milk and serum of dairy cows following vaccination with a cholera toxin A2 and B subunit (CTA2/B) based vaccine containing the iron-regulated surface determinant A (IsdA) and clumping factor A (ClfA) antigens of S. aureus (IsdA + ClfA-CTA2/B). The goal of the current study was to assess the efficacy of this vaccine to protect against S. aureus infection after intramammary challenge. Six mid-lactation heifers were randomized to vaccinated and control groups. On days 1 and 14 animals were inoculated intranasally with vaccine or vehicle control, and on day 20 animals were challenged with S. aureus. Clinical outcome, milk quality, bacterial shedding, and somatic cell count (SCC) were followed for ten days post-challenge. Vaccinated animals did not show signs of clinical S. aureus mastitis and had lower SCCs compared to control animals during the challenge period. Reductions in bacterial shedding were observed but were not significant between groups. Antibody analysis of milk and serum indicated that, upon challenge, vaccinated animals produced enhanced IsdA- and ClfA-CTA2/B specific immunoglobulin G (IgG) responses, while responses to CTA2/B alone were not different between groups. Responses after challenge were largely IgG1 against the IsdA antigen and mixed IgG1/IgG2 against the ClfA antigen. In addition, there was a significant increase in interferon gamma (IFN-γ) expression from blood cells in vaccinated animals on day 20. While preliminary, these findings support evidence of the induction of active immunity by IsdA + ClfA-CTA2/B, and further assessment of this vaccine is warranted.

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Morley, Graeme F., i Geoffrey M. Gadd. "Sorption of toxic metals by fungi and clay minerals". Mycological Research 99, nr 12 (grudzień 1995): 1429–38. http://dx.doi.org/10.1016/s0953-7562(09)80789-2.

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RAMU, J., K. CLARK, G. N. WOODE, A. B. SARR i T. D. PHILLIPS. "Adsorption of Cholera and Heat-Labile Escherichia coli Enterotoxins by Various Adsorbents: an In Vitro Study". Journal of Food Protection 60, nr 4 (1.04.1997): 358–62. http://dx.doi.org/10.4315/0362-028x-60.4.358.

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A variety of common inorganic adsorbents representing aluminas, zeolites, phyllosilicate clays, silica, and carbon were compared for their abilities to adsorb cholera toxin (CT) and heat-labile (LT)Escherichia coli enterotoxin. An appropriate assay system for the enterotoxins was developed using the Y-1 mouse-adrenal-tumor cell line, End points were determined by counting the number of rounded (cytotonic) cells at the relevant dilution. The adsorption varied between 177.0 × 106 and 109.6 × 102 CYTU (cytotonic titer unit) for CT with charcoal and boehmite respectively, and between 60.7 × 104 and 180.4 × 101 CYTU for LT with charcoal and boehmite respectively. Several of the other materials adsorbed CT and LT well, particularly attapulgite and sodium bentonite. The tightness of CT and LT binding to sodium bentonite and charcoal was determined by washing the adsorbent-enterotoxin pellets. Both toxins were strongly adsorbed, with dissociation of only 46.3 × 10° CYTU (<0.01 %) of the bound CT from sodium bentonite and 18.0× 101 CYTU (0.06%) of the bound LT from charcoal. The clay and charcoal pellets were assayed for their cytotonicity. Most of the activity of the adsorbed enterotoxins was lost: 93.1 and 89.6% for CT with sodium bentonite and charcoal, respectively, and 93.8 and 85.9% for LT with sodium bentonite and charcoal, respectively. The effect of dietary protein (casein) in enterotoxin adsorption by clay was also investigated. One percent casein (when adsorbed to sodium bentonite clay) completely blocked the adsorption of CT. When this protein-clay complex was treated with enzymes present in pancreatin, the digestive effect on the casein was sufficient to permit the adsorption of 137.6 × 101 CYTU of CT, although most of the blocking effect of casein remained. Further in vitro studies are needed to model the stomach, pancreatic, and intestinal digestive systems for determining if dietary proteins can block CT adsorption by clay in vivo. These results extend and support previously published data, obtained experimentally in rabbit and rat intestinal loops and from studies of children suffering spontaneous diarrhea, on the beneficial role of clays and other inorganic adsorbents in controlling enterotoxin activity.

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Acosta, Atzel C., Pollyanne Raysa F. Oliveira, Laís Albuquerque, Isamara F. Silva, Elizabeth S. Medeiros, Mateus M. Costa, José Wilton Pinheiro Junior i Rinaldo A. Mota. "Frequency of Staphylococcus aureus virulence genes in milk of cows and goats with mastitis". Pesquisa Veterinária Brasileira 38, nr 11 (listopad 2018): 2029–36. http://dx.doi.org/10.1590/1678-5150-pvb-5786.

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ABSTRACT: The present study determined the frequency of Staphylococcus aureus virulence genes in 2,253 milk samples of cows (n=1000) and goats (n=1253) raised in three different geographical regions of the state Pernambuco, Brazil. The presence of genes of virulence factors associated to adhesion to host cells (fnbA, fnbB, clfA and clfB), toxinosis (sea, seb, sec, sed, seg, seh, sei, tsst, hla and hlb), and capsular polysaccharide (cap5 and cap8) was evaluated by PCR. A total of 123 and 27 S. aureus strains were isolated from cows’ and goats’ milk, respectively. The sec and tsst genes were detected exclusively in goats’ isolates, while the seh gene was only identified in cows’ isolates. The number of toxin genes per strain showed that goats’ isolates are likely more toxic than bovines’ isolates. The cap5 genotype predominated in both host species, especially in strains collected from cows raised in the Agreste region. The cap8 genotype is likely more virulent due to the number of virulence genes per strain. The results of the present study demonstrate that S. aureus may pose a potential threat to human health in Brazil, and, therefore, these results should support actions related to mastitis control programs.

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P S, Dr Anju, i Dr Jaya D S. "Impacts of Clay Mining Activities on Aquatic Ecosystems: A Critical Review". International Journal of Engineering and Advanced Technology 11, nr 4 (30.04.2022): 128–34. http://dx.doi.org/10.35940/ijeat.d3495.0411422.

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The unconsolidated earth surface is a rich source of minerals, of which clay is one of the richest natural minerals, having various natural and anthropogenic properties. Natural clay is widely available as a cheaper resource, which is non toxic to ecosystems and has the property of preserving ground water and aquifers. At the same time, the ubiquitous and widespread occurrence of clay will have the property to control toxic materials. The uncontrolled exploitation or mining of clay minerals will affect the aquatic ecosystem's sustainability in many ways. Water quality is very essential for the healthy environment and human life, whereas unpredictable conditions like flooding, drought, groundwater loss, loss of biodiversity, and health impacts on the surrounding inhabitants are some of the signs of ecosystem loss. The unwanted mined clay is deposited into the surrounding area of the mining environment, resulting in top soil, ground water, and surface water pollution. The review paper describes the pollution aspects of the aquatic ecosystem with special emphasis on ground water, aquifers, fresh water (lotic and lentic), sediment, and marine ecology and hydrology.

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Withey, Jeffrey H., Dhrubajyoti Nag, Sarah C. Plecha, Ritam Sinha i Hemanta Koley. "Conjugated Linoleic Acid Reduces Cholera Toxin ProductionIn VitroandIn Vivoby Inhibiting Vibrio cholerae ToxT Activity". Antimicrobial Agents and Chemotherapy 59, nr 12 (21.09.2015): 7471–76. http://dx.doi.org/10.1128/aac.01029-15.

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ABSTRACTThe severe diarrheal disease cholera is endemic in over 50 countries. Current therapies for cholera patients involve oral and/or intravenous rehydration, often combined with the use of antibiotics to shorten the duration and intensity of the disease. However, as antibiotic resistance increases, treatment options will become limited. Linoleic acid has been shown to be a potent negative effector ofV. choleraevirulence that acts on the major virulence transcription regulator protein, ToxT, to inhibit virulence gene expression. ToxT activates transcription of the two major virulence factors required for disease, cholera toxin (CT) and toxin-coregulated pilus (TCP). A conjugated form of linoleic acid (CLA) is currently sold over the counter as a dietary supplement and is generally recognized as safe by the U.S. Food and Drug Administration. This study examined whether CLA could be used as a new therapy to reduce CT production, which, in turn, would decrease disease duration and intensity in cholera patients. CLA could be used in place of traditional antibiotics and would be very unlikely to generate resistance, as it affects only virulence factor production and not bacterial growth or survival.

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36

Boruah, Jayanta S., i Devasish Chowdhury. "Advances in Carbon Nanomaterial–Clay Nanocomposites for Diverse Applications". Minerals 13, nr 1 (23.12.2022): 26. http://dx.doi.org/10.3390/min13010026.

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Clay materials are widely used in sheet-type platforms with peculiar characteristics and diverse applications. However, due to some disadvantages—such as weak mechanical strength and low reactivity—they are often subjected to modifications. Such tuning leads to better output than pure clay materials. This review describes some of the clay hybrids in the form of nanocomposites with carbon nanomaterials. Generally, graphene oxide or its derivatives—such as reduced graphene oxide, carbon nanotubes, carbon dots, carbon nanoclusters, and polymeric components—have been utilized so far to make efficient clay composites that have applications such as catalysis, wastewater treatment for toxin removal, cargo delivery, stimulus-responsive advanced tools, optoelectronics, mechanically stable films for filtration, etc. It is interesting to note that nearly all of these applications tend to show the efficacy of modified clay nanocomposites as being significantly greater than that of pure clay, especially in terms of mechanical strength, loading capacity, increased surface area, and tunable functionality. According to the literature, the evidence proves the beneficial effects of these clay nanocomposites with carbon nanomaterials.

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37

Venkateswerlu, G., i G. Stotzky. "Binding of the protoxin and toxin proteins ofBacillus thuringiensis subsp.kurstaki on clay minerals". Current Microbiology 25, nr 4 (październik 1992): 225–33. http://dx.doi.org/10.1007/bf01570723.

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Williams, Lynda B. "Geomimicry: harnessing the antibacterial action of clays". Clay Minerals 52, nr 1 (marzec 2017): 1–24. http://dx.doi.org/10.1180/claymin.2017.052.1.01.

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AbstractA decade of research on clays that kill human pathogens, including antibiotic-resistant strains such as methicillin-resistant S. aureus (MRSA), has documented their common characteristics. Worldwide, ∼5% of clays tested to date are antibacterial when hydrated. Most antibacterial clays are from hydrothermally altered volcanics, where volcanogenic fluids produce minerals containing reduced metals. Ferruginous illite-smectite (I-S) is the most common clay mineral, although kaolins dominate some samples. Antibacterial clay mineral assemblages may contain other reduced Fe minerals (e.g. pyrite) that drive production of reactive oxygen species (H2O2, •OH, •O2−) and cause damage to cell membranes and intracellular proteins. Ion exchange can also cause loss of bacterial membrane-bound Ca2+, Mg2+ and PO43–.Critically important is the role of clays in buffering the hydration water pH to conditions where Al and Fe are soluble. A nanometric particle size (<200 nm) is characteristic of antibacterial clays and may be a feature that promotes dissolution. Clay interlayers or the lumen of tubular clays may absorb reduced transition metals, protecting them from oxidation. When the clays are mixed with deionized water for medicinal applications, these metals are released and oxidized.Different antibacterial clays exhibit different modes of action. The minerals may be a source of toxins, or by adsorption may deprive bacteria of essential nutrients. In the field, the pH and Eh (oxidation state) of the hydrated clay may help to identify potential antibacterial clays. If the pH is circum-neutral, toxic metals are not soluble. However, at pH < 5 or >9 many metals are soluble and the oxidation of transition metals increases the Eh of the suspension to >400 mV, leading to bacterial oxidation.Understanding the antibacterial mechanism of natural clay may lead to design of new treatments for antibiotic-resistant bacteria, with potential applications in wound dressings, medical implants ( joint replacements, catheters), animal feed stocks, agricultural pathogens, and production of antibacterial building materials. This research exemplifies how ‘geomimicry’ (copying geochemical processes) may open new frontiers in science.

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39

Kerkez, Djurdja, Milena Becelic-Tomin, Milena Dalmacija, Dragana Tomasevic, Srdjan Roncevic, Gordana Pucar i Bozo Dalmacija. "Leachability and physical stability of solidified and stabilized pyrite cinder sludge from dye effluent treatment". Chemical Industry 69, nr 3 (2015): 231–39. http://dx.doi.org/10.2298/hemind140304036k.

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This work is concerned with exploring the possibilities of using solidification/stabilization (S/S) treatment for toxic sludge generated in dye effluent treatment, when pyrite cinder is used as catalytic iron source in the modified heterogeneous Fenton process. S/S treatment was performed by using different clay materials (kaolin, bentonite and native clay from the territory of Vojvodina) and fly ash in order to immobilize toxic metals and arsenic presented in sludge. For the evaluation of the extraction potential of toxic metals and the effectiveness of the S/S treatment applied, four single-step leaching tests were performed. Leaching test results indicated that all applied S/S treatments were effective in immobilizing toxic metals and arsenic presented in sludge. X-ray diffraction analysis confirmed the formation of pozzolanic products, and compressive strength measurement proved the treatment efficacy. It can be concluded that the S/S technique has significant potential for solving the problem of hazardous industrial waste and its safe disposal.

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40

Waheed, S., Y. Faiz, S. Rahman i N. Siddique. "Toxic element composition of multani mitti clay for nutritional safety". Journal of Radioanalytical and Nuclear Chemistry 295, nr 1 (12.06.2012): 143–50. http://dx.doi.org/10.1007/s10967-012-1876-x.

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Müller, Anna Sonja, Milot Gashi, Klara Janjić, Michael Edelmayer, Andreas Moritz i Hermann Agis. "The impact of clay-based hypoxia mimetic hydrogel on human fibroblasts of the periodontal soft tissue". Journal of Biomaterials Applications 33, nr 9 (13.02.2019): 1277–84. http://dx.doi.org/10.1177/0885328218821042.

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Thixotropic clays have favorable properties for tissue regeneration. Hypoxia mimetic agents showed promising results in pre-clinical models for hard and soft tissue regeneration. It is unclear if clays can be used as carrier for hypoxia mimetic agent in a periodontal regenerative setting. Here, we tested the response of human fibroblasts of the periodontal soft tissue to synthetic clay hydrogels and assessed hypoxia mimetic agent release. Cells were cultured on synthetic clay hydrogels (5.00%–0.15%). We assessed viability and differentiation capacity with resazurin-based toxicity assays, MTT staining, Live-Dead staining, and alkaline phosphatase staining. To reveal the response of fibroblasts to hypoxia mimetic agent-loaded clay hydrogels, cells were exposed to clay supplemented with dimethyloxalylglycine, deferoxamine, l-mimosine, and CoCl2. Supernatants from hypoxia mimetic agent-loaded clay hydrogels were harvested and replaced with medium at hour 1, 3, 6, 24, 48, and 72. To reveal the hypoxia mimetic capacity of supernatants, vascular endothelial growth factor production in the fibroblasts was assessed in the culture medium. Our data show that clay did not induce relevant toxic effects in the fibroblasts which remained capable to differentiate into alkaline phosphatase-positive cells at the relevant concentrations. Fibroblasts cultured on clay hydrogel loaded with dimethyloxalylglycine, deferoxamine, l-mimosine, and CoCl2 remained vital, however, no significant increase in vascular endothelial growth factor levels was found in the culture medium. Only dimethyloxalylglycine-loaded clay supernatants taken in the first hours stimulated vascular endothelial growth factor production in fibroblasts. In conclusion no pronounced toxic effects of synthetic clay were observed. Supplementation with dimethyloxalylglycine leads to hypoxia mimetic activity. This pilot study provides first insights into the impact of synthetic clay on periodontal tissue.

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42

Zhang, Qingfeng, Yuxin Si, Li Yang, Li Wang, Shuijiao Peng, Yiming Chen, Minzhi Chen, Xi Zhou i Zhonghua Liu. "Two Novel Peptide Toxins from the Spider Cyriopagopus longipes Inhibit Tetrodotoxin-Sensitive Sodium Channels". Toxins 12, nr 9 (19.08.2020): 529. http://dx.doi.org/10.3390/toxins12090529.

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Sodium channels play a critical role in the generation and propagation of action potentials in excitable tissues, such as nerves, cardiac muscle, and skeletal muscle, and are the primary targets of toxins found in animal venoms. Here, two novel peptide toxins (Cl6a and Cl6b) were isolated from the venom of the spider Cyriopagopus longipes and characterized. Cl6a and Cl6b were shown to be inhibitors of tetrodotoxin-sensitive (TTX-S), but not TTX-resistant, sodium channels. Among the TTX-S channels investigated, Cl6a and Cl6b showed the highest degree of inhibition against NaV1.7 (half-maximal inhibitory concentration (IC50) of 11.0 ± 2.5 nM and 18.8 ± 2.4 nM, respectively) in an irreversible manner that does not alter channel activation, inactivation, or repriming kinetics. Moreover, analysis of NaV1.7/NaV1.8 chimeric channels revealed that Cl6b is a site 4 neurotoxin. Site-directed mutagenesis analysis indicated that D816, V817, and E818 observably affected the efficacy of the Cl6b-NaV1.7 interaction, suggesting that these residues might directly affect the interaction of NaV1.7 with Cl6b. Taken together, these two novel peptide toxins act as potent and sustained NaV1.7 blockers and may have potential in the pharmacological study of sodium channels.

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Ibigbami, Tope B., Adedapo O. Adeola, David B. Olawade, Odunayo T. Ore, Babatunde O. Isaac i Alabi A. Sunkanmi. "Pristine and activated bentonite for toxic metal removal from wastewater". Water Practice and Technology 17, nr 3 (22.02.2022): 784–97. http://dx.doi.org/10.2166/wpt.2022.018.

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Abstract Natural bentonite clay (NBC) was activated using nitric acid (HNO3). Characterization techniques including FTIR, SEM, XRD and BET were employed to examine the morphology of NBC and ABC (activated bentonite clay) sorbents. Comparative application of ABC and NBC to remove heavy metals (Fe2+, Zn2+, Ni2+) from pharmaceutical effluents was investigated under various experimental conditions. The maximum proportional removal by ABC was 88.90, 81.80 and 75.50% at pH 8, and 63.90, 59.60, 58.70% at pH 10 for NBC, both for Zn2+, Fe2+ and Ni2+ respectively. The Freundlich multilayer adsorption model and pseudo-second-order kinetics best fit the experimental data, suggesting the formation of multiple adsorption layers via strong ionic and electrostatic interactions. Heavy metals adsorption is more favorable with ABC than NBC, due to the availability of more sorption sites and a larger specific surface. The thermodynamic parameters (ΔH°, ΔS°, and ΔG°) revealed that the adsorption is endothermic and spontaneous in nature for both ABC and NBC.

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Zotiadis, V., i A. Argyraki. "Development of innovative environmental applications of attapulgite clay". Bulletin of the Geological Society of Greece 47, nr 2 (24.01.2017): 992. http://dx.doi.org/10.12681/bgsg.11139.

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In this paper we present a series of laboratory and field, pilot- scale applications of attapulgite clay as an amendment for the stabilization of metals in contaminated soil and sewage sludge. Attapulgite’s structure together with its fine particle size and fibrous habit are responsible for its high specific surface area and sorption properties. A pilot scale application of attapulgite clay as a binder for in situ stabilization of toxic metals in contaminated land showed significant reduction in the water leachable metal fraction (Cu: 17%, Pb: 50%, Zn: 45%, Cd: 41%, Ag: 46%, As: 18%, Mn: 47%, Ba: 45%, Sb: 29%). In a second pilot scale environmental application, an innovative attapulgite “Geosynthetic Reactive Clay - GRC” was designed and developed for “capping” and “stabilization”of toxic metals in contaminated soil. Also, laboratory scale experiments with fresh sewage sludge from a municipal water treatment plant showed that addition of attapulgite clay in sludge, significantly reduced the leachable concentrations of phenol, DOC, Hg, Cu, Mo, Pb, Se, As, Zn and pathogen population over a 4 weeks observation period. The developed soil remediation techniques are promising and cost-effective under present market conditions. Concerning treatment of sewage sludge, attapulgite clay is an effective additive that could enhance the composting procedure creating an environmental added value, final compost product.

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Ntwampe, I. O. "Treatment of AMD using a combination of saw dust, bentonite clay and phosphate in the removal of turbid materials and toxic metals". Water Practice and Technology 16, nr 2 (18.02.2021): 541–56. http://dx.doi.org/10.2166/wpt.2021.014.

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Abstract Acid mine drainage collected from the western decant in South Africa was treated in a series of small-scale laboratory experiments. 200 mL of the sample was poured into five 500 mL glass beakers using flocculants formed by mixing size-optimized 1.5 g of bentonite clay with 3.5 g saw dust and 1.0 g of Na3PO4 in triplicates (experiment A). Four similar sets of control experiments were conducted using the same amount of bentonite clay and saw dust with varying Na3PO4, contents in AMD treatment; the rationale being to determine the efficiency of Na3PO4 (experiments B, C and D). The results show that conductivity has an influence in the removal of the turbid materials. The removal efficiency of toxic metals using a flocculant containing 220 μm bentonite clay particle size and 0.012 or 0.25 M of Na3PO4 is higher than 96% when compared to that of the samples dosed with a flocculant containing 0.05 M Na3PO4, which is less than 91%. The flocculant also showed optimal removal efficiency of both turbid materials and toxic metals, i.e. removal efficiency within a range 96.5–99.3%. The flocculants containing 0.025 M Na3PO4 showed optimal removal efficiency of turbidity, colour, toxic metals and natural organic compounds.

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Cherifi, Badia Imene, Mohammed Belbachir i Souad Bennabi. "Green Polymerization of Vinyl Acetate Using Maghnite-Na+, an Exchanged Montmorillonite Clay, as an Ecologic Catalyst". Chemistry & Chemical Technology 15, nr 2 (15.05.2021): 183–90. http://dx.doi.org/10.23939/chcht15.02.183.

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In this work, the green polymerization of vinyl acetate is carried out by a new method which consists in the use of clay called Maghnite-Na+ as an ecological catalyst, non-toxic, inexpensive and recyclable by a simple filtration. X-ray diffraction and scanning electron microscopy showed that Maghnite-Na+ is successfully obtained after cationic treatment (sodium) on crude maghnite. It is an effective alternative to replace toxic catalysts such as benzoyl peroxide and azobisisobutyronitrile which are mostly used during the synthesis of polyvinyl acetate (PVAc) making the polymerization reaction less problematic for the environment. The synthesis reaction is less energetic by the use of recycled polyurethane as a container for the reaction mixture and is considered as a renewable material and a good thermal insulator maintaining the temperature of 273 K for 6 h. The reaction in bulk is also preferred to avoid the use of a solvent and therefore to stay in the context of green chemistry. In these conditions, the structure of obtained polymer is established by 1H NMR and 13C NMR. Infrared spectroscopy (FT-IR) was also used to confirm the structure of PVAc. Thermogravimetric analysis showed that it is thermally stable and starts to degrade at 603 K while differential scanning calorimetry showed that this polymer has a glass transition temperature Tg of 323 K.

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Lhotka, M., V. Machovič i B. Doušová. "Preparation of modified sorbents from rehydrated clay materials". Clay Minerals 47, nr 2 (czerwiec 2012): 251–58. http://dx.doi.org/10.1180/claymin.2012.047.2.08.

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AbstractThe use of clay materials as selective sorbents for different contaminants requires very efficient methods. A natural kaolinite was calcined to metakaolinite and than rehydrated at different temperatures to produce a highly porous sorbent. The kinetics of this process were measured, with subsequent IR characterization of the phases formed. The surface and pore distribution of new phases were also assigned. In addition, the kaolinite obtained was pre-treated with Fe3+ ions to improve its sorption affinity for anionic particles. The rehydrated kaolinite and its Fe-modification were used for the adsorption of toxic cations (Zn, Cd, Pb) and anions (As, Se). Adsorption capacities depending on the physical chemical properties of the initial solution (pH, concentration of toxic ions) and the surface properties of the sorbent (specific surface area, modification method) were investigated. The adsorption properties of the sorbents were defined by the Langmuir model.

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Flemming, C. A., F. G. Ferris, T. J. Beveridge i G. W. Bailey. "Remobilization of toxic heavy metals adsorbed to bacterial wall-clay composites." Applied and Environmental Microbiology 56, nr 10 (1990): 3191–203. http://dx.doi.org/10.1128/aem.56.10.3191-3203.1990.

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Hayrapetyan, Suren, Antonios Kelarakis, Luis Estevez, Qin Lin, Kausik Dana, Yi-Lin Chung i Emmanuel P. Giannelis. "Non-toxic poly(ethylene terephthalate)/clay nanocomposites with enhanced barrier properties". Polymer 53, nr 2 (styczeń 2012): 422–26. http://dx.doi.org/10.1016/j.polymer.2011.12.017.

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Sengco, Mario R., Johannes A. Hagström, Edna Granéli i Donald M. Anderson. "Removal of Prymnesium parvum (Haptophyceae) and its toxins using clay minerals". Harmful Algae 4, nr 2 (luty 2005): 261–74. http://dx.doi.org/10.1016/j.hal.2004.05.001.

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