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McMillin, David E., Lycurgus L. Muldrow e Shwanda J. Laggette. "Simultaneous detection of toxin A and toxin B genetic determinants of Clostridium difficile using the multiplex polymerase chain reaction". Canadian Journal of Microbiology 38, n.º 1 (1 de janeiro de 1992): 81–83. http://dx.doi.org/10.1139/m92-013.
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A multiplex polymerase chain reaction was developed to simultaneously detect the presence of toxin A and toxin B genes of Clostridium difficile. A 1050-bp fragment of the toxin B gene and a 1217-bp fragment of the toxin A gene were amplified from 42 toxic strains of C. difficile; however, from 10 nontoxic strains the toxin gene fragments were not amplified; these data demonstrate that this multiplex polymerase chain reaction procedure can be used to differentiate between toxic and nontoxic strains. This sensitive and specific multiplex polymerase chain reaction for C. difficile toxins may prove to be a valuable diagnostic procedure. Key words: Clostridium difficile, polymerase chain reaction, bacterial toxins.
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Archana, M. S. "Toxin yet not toxic: Botulinum toxin in dentistry". Saudi Dental Journal 28, n.º 2 (abril de 2016): 63–69. http://dx.doi.org/10.1016/j.sdentj.2015.08.002.
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Qu, Jiangqi, Liping Shen, Meng Zhao, Wentong Li, Chengxia Jia, Hua Zhu e Qingjing Zhang. "Determination of the Role of Microcystis aeruginosa in Toxin Generation Based on Phosphoproteomic Profiles". Toxins 10, n.º 7 (23 de julho de 2018): 304. http://dx.doi.org/10.3390/toxins10070304.
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Microcystis aeruginosa is the most common species responsible for toxic cyanobacterial blooms and is considered a significant contributor to the production of cyanotoxins, particularly the potent liver toxins called microcystins. Numerous studies investigating Microcystis spp. blooms have revealed their deleterious effects in freshwater environments. However, the available knowledge regarding the global phosphoproteomics of M. aeruginosa and their regulatory roles in toxin generation is limited. In this study, we conducted comparative phosphoproteomic profiling of non-toxic and toxin-producing strains of M. aeruginosa. We identified 59 phosphorylation sites in 37 proteins in a non-toxic strain and 26 phosphorylation sites in 18 proteins in a toxin-producing strain. The analysis of protein phosphorylation abundances and functions in redox homeostasis, energy metabolism, light absorption and photosynthesis showed marked differences between the non-toxic and toxin-producing strains of M. aeruginosa, indicating that these processes are strongly related to toxin generation. Moreover, the protein-protein interaction results indicated that BJ0JVG8 can directly interact with the PemK-like toxin protein B0JQN8. Thus, the phosphorylation of B0JQN8 appears to be associated with the regulatory roles of toxins in physiological activity.
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Possani, L. D., B. M. Martin, I. Svendsen, G. S. Rode e B. W. Erickson. "Scorpion toxins from Centruroides noxius and Tityus serrulatus. Primary structures and sequence comparison by metric analysis". Biochemical Journal 229, n.º 3 (1 de agosto de 1985): 739–50. http://dx.doi.org/10.1042/bj2290739.
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The complete primary structures of toxin II-14 from the Mexican scorpion Centruroides noxius Hoffmann and toxin gamma from the Brazilian scorpion Tityus serrulatus Lutz and Mello have been determined. Cleavage of toxin gamma after Met-6 with CNBr produced the 55-residue peptide 7-61, which maintained the four disulphide bonds but was not toxic to mice at a dose 3 times the lethal dose of native toxin gamma. Pairwise comparison by metric analysis of segment 1-50 of toxin gamma and the corresponding segments from two other South American scorpion toxins, five North American scorpion toxins, nine North African scorpion toxins and one Central Asian scorpion toxin showed that the three Brazilian toxins are intermediate between the North American and North African toxins. This result is consistent with the hypothesis that the South American and African continents were joined by a land connection in the distant past.
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Roderer, Daniel, e Stefan Raunser. "Tc Toxin Complexes: Assembly, Membrane Permeation, and Protein Translocation". Annual Review of Microbiology 73, n.º 1 (8 de setembro de 2019): 247–65. http://dx.doi.org/10.1146/annurev-micro-102215-095531.
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Tc toxin complexes are virulence factors of many bacteria, including insect and human pathogens. Tc toxins are composed of three subunits that act together to perforate the host membrane, similar to a syringe, and translocate toxic enzymes into the host cell. The reactions of the toxic enzymes lead to deterioration and ultimately death of the cell. We review recent high-resolution structural and functional data that explain the mechanism of action of this type of bacterial toxin at an unprecedented level of molecular detail. We focus on the steps that are necessary for toxin activation and membrane permeation. This is where the largest conformational transitions appear. Furthermore, we compare the architecture and function of Tc toxins with those of anthrax toxin and vertebrate teneurin.
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Hanna, B. A. "Toxic shock syndrome toxin". JAMA: The Journal of the American Medical Association 254, n.º 15 (18 de outubro de 1985): 2062b—2062. http://dx.doi.org/10.1001/jama.254.15.2062b.
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Hanna, Bruce A. "Toxic Shock Syndrome Toxin". JAMA: The Journal of the American Medical Association 254, n.º 15 (18 de outubro de 1985): 2062. http://dx.doi.org/10.1001/jama.1985.03360150038011.
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Blanco, Juan. "Accumulation of Dinophysis Toxins in Bivalve Molluscs". Toxins 10, n.º 11 (2 de novembro de 2018): 453. http://dx.doi.org/10.3390/toxins10110453.
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Several species of the dinoflagellate genus Dinophysis produce toxins that accumulate in bivalves when they feed on populations of these organisms. The accumulated toxins can lead to intoxication in consumers of the affected bivalves. The risk of intoxication depends on the amount and toxic power of accumulated toxins. In this review, current knowledge on the main processes involved in toxin accumulation were compiled, including the mechanisms and regulation of toxin acquisition, digestion, biotransformation, compartmentalization, and toxin depuration. Finally, accumulation kinetics, some models to describe it, and some implications were also considered.
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Goulard, Céline, Sophie Langrand, Elisabeth Carniel e Sylvie Chauvaux. "The Yersinia pestis Chromosome Encodes Active Addiction Toxins". Journal of Bacteriology 192, n.º 14 (14 de maio de 2010): 3669–77. http://dx.doi.org/10.1128/jb.00336-10.
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ABSTRACT Toxin-antitoxin (TA) loci consist of two genes in an operon, encoding a stable toxin and an unstable antitoxin. The expression of toxin leads to cell growth arrest and sometimes bacterial death, while the antitoxin prevents the cytotoxic activity of the toxin. In this study, we show that the chromosome of Yersinia pestis, the causative agent of plague, carries 10 putative TA modules and two solitary antitoxins that belong to five different TA families (HigBA, HicAB, RelEB, Phd/Doc, and MqsRA). Two of these toxin genes (higB2 and hicA1) could not be cloned in Escherichia coli unless they were coexpressed with their cognate antitoxin gene, indicating that they are highly toxic for this species. One of these toxin genes (higB2) could, however, be cloned directly and expressed in Y. pestis, where it was highly toxic, while the other one (hicA1) could not, probably because of its extreme toxicity. All eight other toxin genes were successfully cloned into the expression vector pBAD-TOPO. For five of them (higB1, higB3, higB5, hicA2, and tox), no toxic activity was detected in either E. coli or Y. pestis despite their overexpression. The three remaining toxin genes (relE1, higB4, and doc) were toxic for E. coli, and this toxic activity was abolished when the cognate antitoxin was coexpressed, showing that these three TA modules are functional in E. coli. Curiously, only one of these three toxins (RelE1) was active in Y. pestis. Cross-interaction between modules of the same family was observed but occurred only when the antitoxins were almost identical. Therefore, our study demonstrates that of the 10 predicted TA modules encoded by the Y. pestis chromosome, at least 5 are functional in E. coli and/or in Y. pestis. This is the first demonstration of active addiction toxins produced by the plague agent.
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Loh, Zhi Hung, Diane Ouwerkerk, Athol V. Klieve, Natasha L. Hungerford e Mary T. Fletcher. "Toxin Degradation by Rumen Microorganisms: A Review". Toxins 12, n.º 10 (20 de outubro de 2020): 664. http://dx.doi.org/10.3390/toxins12100664.
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Animal feeds may contain exogenous compounds that can induce toxicity when ruminants ingest them. These toxins are secondary metabolites originating from various sources including plants, bacteria, algae and fungi. Animal feed toxins are responsible for various animal poisonings which negatively impact the livestock industry. Poisoning is more frequently reported in newly exposed, naïve ruminants while ‘experienced’ ruminants are observed to better tolerate toxin-contaminated feed. Ruminants can possess detoxification ability through rumen microorganisms with the rumen microbiome able to adapt to utilise toxic secondary metabolites. The ability of rumen microorganisms to metabolise these toxins has been used as a basis for the development of preventative probiotics to confer resistance against the poisoning to naïve ruminants. In this review, detoxification of various toxins, which include plant toxins, cyanobacteria toxins and plant-associated fungal mycotoxins, by rumen microorganisms is discussed. The review will include clinical studies of the animal poisoning caused by these toxins, the toxin mechanism of action, toxin degradation by rumen microorganisms, reported and hypothesised detoxification mechanisms and identified toxin metabolites with their toxicity compared to their parent toxin. This review highlights the commercial potential of rumen inoculum derived probiotics as viable means of improving ruminant health and production.
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Kobayashi, Kazuo. "Diverse LXG toxin and antitoxin systems specifically mediate intraspecies competition in Bacillus subtilis biofilms". PLOS Genetics 17, n.º 7 (19 de julho de 2021): e1009682. http://dx.doi.org/10.1371/journal.pgen.1009682.
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Biofilms are multispecies communities, in which bacteria constantly compete with one another for resources and niches. Bacteria produce many antibiotics and toxins for competition. However, since biofilm cells exhibit increased tolerance to antimicrobials, their roles in biofilms remain controversial. Here, we showed that Bacillus subtilis produces multiple diverse polymorphic toxins, called LXG toxins, that contain N-terminal LXG delivery domains and diverse C-terminal toxin domains. Each B. subtilis strain possesses a distinct set of LXG toxin–antitoxin genes, the number and variation of which is sufficient to distinguish each strain. The B. subtilis strain NCIB3610 possesses six LXG toxin–antitoxin operons on its chromosome, and five of the toxins functioned as DNase. In competition assays, deletion mutants of any of the six LXG toxin–antitoxin operons were outcompeted by the wild-type strain. This phenotype was suppressed when the antitoxins were ectopically expressed in the deletion mutants. The fitness defect of the mutants was only observed in solid media that supported biofilm formation. Biofilm matrix polymers, exopolysaccharides and TasA protein polymers were required for LXG toxin function. These results indicate that LXG toxin-antitoxin systems specifically mediate intercellular competition between B. subtilis strains in biofilms. Mutual antagonism between some LXG toxin producers drove the spatial segregation of two strains in a biofilm, indicating that LXG toxins not only mediate competition in biofilms, but may also help to avoid warfare between strains in biofilms. LXG toxins from strain NCIB3610 were effective against some natural isolates, and thus LXG toxin–antitoxin systems have ecological impact. B. subtilis possesses another polymorphic toxin, WapA. WapA had toxic effects under planktonic growth conditions but not under biofilm conditions because exopolysaccharides and TasA protein polymers inhibited WapA function. These results indicate that B. subtilis uses two types of polymorphic toxins for competition, depending on the growth mode.
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Yusof, Tengku Nadiah, Mohd Rafatullah, Rohaslinda Mohamad, Norli Ismail, Zarina Zainuddin e Japareng Lalung. "Cyanobacteria Characteristics and Methods for Isolation and Accurate Identification of Cyanotoxins: A Review Article". Avicenna Journal of Environmental Health Engineering 4, n.º 1 (30 de junho de 2017): 10051. http://dx.doi.org/10.5812/ajehe.10051.
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Cyanobacteria are bacteria found in different ecosystems, such as lakes and rocks. These bacteria, capable of photosynthesis, are important sources of oxygen. However, some cyanobacterial strains can produce toxins, which are harmful to humans and animals. Therefore, collection of epidemiological and surveillance data on cyanobacterial toxins in the environment is vital to ensure a low risk of exposure to toxins in other organisms. For presentation of accurate data on environmental cyanobacterial toxins, it is essential to understand their characteristics, including taxonomy, toxin proteins, and genomic structures, and determine their environmental effects on bacterial populations and toxin production. Taxonomy, which is the scientific classification of organisms, is important in identifying species producing toxins. The structure of toxin proteins and their stability in the environment allow researchers to detect toxins with analytical methods and discuss their limitations. Onthe other hand, identifying toxins via molecular typing enables researchers to investigate toxic cyanobacteria by detecting toxin-encoding genes and toxin gene expression. Meanwhile, environmental factors, such as nutrient level, light intensity, and biotic factors, allow researchers to predict the suitable time and location for accurate sampling. In this review, these cyanobacterial features, which are important for accurate detection of cyanobacterial toxins, will be discussed.
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TSIOURIS (Β.Σ. ΤΣΙΟΥΡΗΣ), V. S., I. GEORGOPOULOU (ΓΕΩΡΓΟΠΟΥΛΟΥ) e E. PETRIDOU (Ε. ΠΕΤΡΙΔΟΥ). "Update on the toxins of Clostridium perfringens and their actions". Journal of the Hellenic Veterinary Medical Society 61, n.º 3 (17 de novembro de 2017): 241. http://dx.doi.org/10.12681/jhvms.14892.
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Clostridia appeared as a distinct class, approximately 2.7 billion years ago, before the initial formation of oxygen. Clostridium perfringens is widely distributed throughout the environment due to its ability to form spores. Furthermore, it is a member of intestinal microbiota in animals and human. In 2002, the complete genome of C perfringens strain 13 was published. Genomic analysis has revealed that C. perfringens lacks the genetic machinery to produce 13 essential amino acids and it obtains these in vivo via the action of its toxins. Toxins of C perfringens can be divided into major, minor and enterotoxin. C perfringens strains are classified into five toxinotypes (A, B, C, D and E), based on the production of four major toxins. Alpha toxin is the best and most studied major toxin of C perfringens and it was the first bacterial toxin established to possess enzymatic activity. It has haemolytic, necrotic and cytolytic activity, it can lyse platelets and leukocytes and it can damage fibroblasts and muscle cell membranes. Expression of epa gene, which is responsible for the production of alpha toxin by C perfringens, is down-regulated in the normal healthy gut, but it is upregulated to initiate enteric disease in response to an environmental signal. C perfringens appears to be regulated in a quorum sensing manner, using oligopeptides, AI-2 or both, to regulate expression of the epa gene, and thus the synthesis of alpha toxin. Beta toxin is recognized as an important agent in necrotic enteritis of humans and it is the second most lethal C. perfringens toxin following epsilon toxin. Beta toxin is a membrane spanning protein that oligomerizes to form channels in susceptible cells or it primarily acts as a neurotoxin. Epsilon toxin is the most potent of the C. perfringens toxins and the third most potent neurotoxin from the Clostridium spp., following botulinum and tetanus toxins. Epsilon toxin of C perfringens type D causes enterotoxaemia and pulpy kidneys disease of lambs. Iota toxin causes disruption of the actin cytoskeleton and cell barrier integrity and it is the less toxic of the major toxins of C perfringens. Although C perfringens enterotoxin is not classified as one of the major toxins of C perfringens, it is the third most common cause of food poisoning in industrialized nations. It is not secreted by the cells of growing bacteria, but it is released only with the sporulation of C perfringens. Not all strains of C perfringens carry the epe gene, which is responsible for the production of enterotoxin. Theta toxin is a pore-forming cytolysin that can lyse red blood cells. It is produced by all types of C perfringens. Together with alpha-toxin, theta-toxin modulates the host inflammatory response. ß2 toxin is a pore forming toxin which is involved in necrotic enteritis of swine and horse, in haemorragic enteritis of bovine in diarrhea cases of dogs and along with enterotoxin in diarrhea cases of humans. Recently, -NetB, a novel toxin that is associated with broiler necrotic enteritis, has been described. The mechanism of its action seems to involve the formation of small hydrophilic pores. Other toxins of C. perfringens include λ-toxin, ô-toxin, μ-toxin, v-toxin, κ-toxin, a-clostripain like protease and neuraminidase/sialidase. These toxins can act as enzymes, while many of them can act synergically or supplementally with major pore forming toxins. Potentially, C. perfringens might produce more toxins, which have not been identified. Finally, the actions of C. perfringens toxins, major or minor, in some diseases have not been figured out.
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Andres, John Kristoffer, Aletta T. Yñiguez, Jennifer Mary Maister, Andrew D. Turner, Dave Eldon B. Olano, Jenelyn Mendoza, Lilibeth Salvador-Reyes e Rhodora V. Azanza. "Paralytic Shellfish Toxin Uptake, Assimilation, Depuration, and Transformation in the Southeast Asian Green-Lipped Mussel (Perna viridis)". Toxins 11, n.º 8 (9 de agosto de 2019): 468. http://dx.doi.org/10.3390/toxins11080468.
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Bivalve molluscs represent an important food source within the Philippines, but the health of seafood consumers is compromised through the accumulation of harmful algal toxins in edible shellfish tissues. In order to assess the dynamics of toxin risk in shellfish, this study investigated the uptake, depuration, assimilation, and analogue changes of paralytic shellfish toxins in Perna viridis. Tank experiments were conducted where mussels were fed with the toxic dinoflagellate Alexandrium minutum. Water and shellfish were sampled over a six day period to determine toxin concentrations in the shellfish meat and water, as well as algal cell densities. The maximum summed toxin concentration determined was 367 µg STX eq./100 g shellfish tissue, more than six times higher than the regulatory action limit in the Philippines. Several uptake and depuration cycles were observed during the study, with the first observed within the first 24 h coinciding with high algal cell densities. Toxin burdens were assessed within different parts of the shellfish tissue, with the highest levels quantified in the mantle during the first 18 h period but shifting towards the gut thereafter. A comparison of toxin profile data evidenced the conversion of GTX1,4 in the source algae to the less potent GTX2,3 in the shellfish tissue. Overall, the study illustrated the temporal variability in Perna viridis toxin concentrations during a modelled algal bloom event, and the accumulation of toxin from the water even after toxic algae were removed.
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de Melo, Janaina Viana, Gareth Wyn Jones, Colin Berry, Romero Henrique Teixeira Vasconcelos, Cláudia Maria Fontes de Oliveira, André Freire Furtado, Christina Alves Peixoto e Maria Helena Neves Lobo Silva-Filha. "Cytopathological Effects of Bacillus sphaericus Cry48Aa/Cry49Aa Toxin on Binary Toxin-Susceptible and -Resistant Culex quinquefasciatus Larvae". Applied and Environmental Microbiology 75, n.º 14 (5 de junho de 2009): 4782–89. http://dx.doi.org/10.1128/aem.00811-09.
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ABSTRACT The Cry48Aa/Cry49Aa mosquitocidal two-component toxin was recently characterized from Bacillus sphaericus strain IAB59 and is uniquely composed of a three-domain Cry protein toxin (Cry48Aa) and a binary (Bin) toxin-like protein (Cry49Aa). Its mode of action has not been elucidated, but a remarkable feature of this protein is the high toxicity against species from the Culex complex, besides its capacity to overcome Culex resistance to the Bin toxin, the major insecticidal factor in B. sphaericus-based larvicides. The goal of this work was to investigate the ultrastructural effects of Cry48Aa/Cry49Aa on midgut cells of Bin-toxin-susceptible and -resistant Culex quinquefasciatus larvae. The major cytopathological effects observed after Cry48Aa/Cry49Aa treatment were intense mitochondrial vacuolation, breakdown of endoplasmic reticulum, production of cytoplasmic vacuoles, and microvillus disruption. These effects were similar in Bin-toxin-susceptible and -resistant larvae and demonstrated that Cry48Aa/Cry49Aa toxin interacts with and displays toxic effects on cells lacking receptors for the Bin toxin, while B. sphaericus IAB59-resistant larvae did not show mortality after treatment with Cry48Aa/Cry49Aa toxin. The cytopathological alterations in Bin-toxin-resistant larvae provoked by Cry48Aa/Cry49Aa treatment were similar to those observed when larvae were exposed to a synergistic mixture of Bin/Cry11Aa toxins. Such effects seemed to result from a combined action of Cry-like and Bin-like toxins. The complex effects caused by Cry48Aa/Cry49Aa provide evidence for the potential of these toxins as active ingredients of a new generation of biolarvicides that conjugate insecticidal factors with distinct sites of action, in order to manage mosquito resistance.
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Sivonen, Kaarina. "Cyanobacterial toxins and toxin production". Phycologia 35, sup6 (novembro de 1996): 12–24. http://dx.doi.org/10.2216/i0031-8884-35-6s-12.1.
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Nonin-Lecomte, Sylvie, Laurence Fermon, Brice Felden e Marie-Laure Pinel-Marie. "Bacterial Type I Toxins: Folding and Membrane Interactions". Toxins 13, n.º 7 (14 de julho de 2021): 490. http://dx.doi.org/10.3390/toxins13070490.
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Bacterial type I toxin-antitoxin systems are two-component genetic modules that encode a stable toxic protein whose ectopic overexpression can lead to growth arrest or cell death, and an unstable RNA antitoxin that inhibits toxin translation during growth. These systems are widely spread among bacterial species. Type I antitoxins are cis- or trans-encoded antisense small RNAs that interact with toxin-encoding mRNAs by pairing, thereby inhibiting toxin mRNA translation and/or inducing its degradation. Under environmental stress conditions, the up-regulation of the toxin and/or the antitoxin degradation by specific RNases promote toxin translation. Most type I toxins are small hydrophobic peptides with a predicted α-helical transmembrane domain that induces membrane depolarization and/or permeabilization followed by a decrease of intracellular ATP, leading to plasmid maintenance, growth adaptation to environmental stresses, or persister cell formation. In this review, we describe the current state of the art on the folding and the membrane interactions of these membrane-associated type I toxins from either Gram-negative or Gram-positive bacteria and establish a chronology of their toxic effects on the bacterial cell. This review also includes novel structural results obtained by NMR concerning the sprG1-encoded membrane peptides that belong to the sprG1/SprF1 type I TA system expressed in Staphylococcus aureus and discusses the putative membrane interactions allowing the lysis of competing bacteria and host cells.
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Mesterhazy, Akos, Denes Szieberth, Eva Tóth Toldine, Zoltan Nagy, Balázs Szabó, Beata Herczig, Istvan Bors e Beata Tóth. "Updating the Methodology of Identifying Maize Hybrids Resistant to Ear Rot Pathogens and Their Toxins—Artificial Inoculation Tests for Kernel Resistance to Fusarium graminearum, F. verticillioides, and Aspergillus flavus". Journal of Fungi 8, n.º 3 (11 de março de 2022): 293. http://dx.doi.org/10.3390/jof8030293.
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Resistance to toxigenic fungi and their toxins in maize is a highly important research topic, as mean global losses are estimated at about 10% of the yield. Resistance and toxin data of the hybrids are mostly not given, so farmers are not informed about the food safety risks of their grown hybrids. According to the findings aflatoxin regularly occurs at preharvest in Hungary and possibly other countries in the region can be jeopardized. We tested, with an improved methodology (two isolates, three pathogens, and a toxin control), 18 commercial hybrids (2017–2020) for kernel resistance (%), and for toxin contamination separately by two–two isolates of F. graminearum, F. verticillioides (mg/kg), and A. flavus (μg/kg). The preharvest toxin contamination was measured in the controls. Highly significant kernel resistance and toxin content differences were identified between hybrids to the different fungi. Extreme high toxin production was found for each toxic species. Only about 10–15% of the hybrids showed higher resistance to the fungal species tested and lower contamination level of their toxins. The lacking correlations between resistance to different fungi and toxins suggest that resistance to different fungi and response to toxin contamination inherits independently, so a toxin analysis is necessary. For safety risk estimation, separated artificial and natural kernel infection and toxin data are needed against all pathogens. Higher resistance to A. flavus and F. verticillioides stabilizes or improves feed safety in hot and dry summers, balancing the harmful effect of climate changes. Resistance and toxin tests during variety registration is an utmost necessity. The exclusion of susceptible or highly susceptible hybrids from commercial production results in reduced toxin contamination.
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McCormick, Susan P., Neil P. J. Price e Cletus P. Kurtzman. "Glucosylation and Other Biotransformations of T-2 Toxin by Yeasts of the Trichomonascus Clade". Applied and Environmental Microbiology 78, n.º 24 (5 de outubro de 2012): 8694–702. http://dx.doi.org/10.1128/aem.02391-12.
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ABSTRACTTrichothecenes are sesquiterpenoid toxins produced byFusariumspecies. Since these mycotoxins are very stable, there is interest in microbial transformations that can remove toxins from contaminated grain or cereal products. Twenty-three yeast species assigned to theTrichomonascusclade (Saccharomycotina, Ascomycota), including fourTrichomonascusspecies and 19 anamorphic species presently classified inBlastobotrys, were tested for their ability to convert the trichothecene T-2 toxin to less-toxic products. These species gave three types of biotransformations: acetylation to 3-acetyl T-2 toxin, glycosylation to T-2 toxin 3-glucoside, and removal of the isovaleryl group to form neosolaniol. Some species gave more than one type of biotransformation. ThreeBlastobotrysspecies converted T-2 toxin into T-2 toxin 3-glucoside, a compound that has been identified as a masked mycotoxin inFusarium-infected grain. This is the first report of a microbial whole-cell method for producing trichothecene glycosides, and the potential large-scale availability of T-2 toxin 3-glucoside will facilitate toxicity testing and development of methods for detection of this compound in agricultural and other products.
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Gacesa, Ranko, David J. Barlow e Paul F. Long. "Machine learning can differentiate venom toxins from other proteins having non-toxic physiological functions". PeerJ Computer Science 2 (10 de outubro de 2016): e90. http://dx.doi.org/10.7717/peerj-cs.90.
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Ascribing function to sequence in the absence of biological data is an ongoing challenge in bioinformatics. Differentiating the toxins of venomous animals from homologues having other physiological functions is particularly problematic as there are no universally accepted methods by which to attribute toxin function using sequence data alone. Bioinformatics tools that do exist are difficult to implement for researchers with little bioinformatics training. Here we announce a machine learning tool called ‘ToxClassifier’ that enables simple and consistent discrimination of toxins from non-toxin sequences with >99% accuracy and compare it to commonly used toxin annotation methods. ‘ToxClassifer’ also reports the best-hit annotation allowing placement of a toxin into the most appropriate toxin protein family, or relates it to a non-toxic protein having the closest homology, giving enhanced curation of existing biological databases and new venomics projects. ‘ToxClassifier’ is available for free, either to download (https://github.com/rgacesa/ToxClassifier) or to use on a web-based server (http://bioserv7.bioinfo.pbf.hr/ToxClassifier/).
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JAMES, K. J., B. CAREY, J. O'HALLORAN, F. N. A. M. van PELT e Z. ŠKRABÁKOVÁ. "Shellfish toxicity: human health implications of marine algal toxins". Epidemiology and Infection 138, n.º 7 (23 de abril de 2010): 927–40. http://dx.doi.org/10.1017/s0950268810000853.
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SUMMARYFive major human toxic syndromes caused by the consumption of shellfish contaminated by algal toxins are presented. The increased risks to humans of shellfish toxicity from the prevalence of harmful algal blooms (HABs) may be a consequence of large-scale ecological changes from anthropogenic activities, especially increased eutrophication, marine transport and aquaculture, and global climate change. Improvements in toxin detection methods and increased toxin surveillance programmes are positive developments in limiting human exposure to shellfish toxins.
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Mantzouki, Evanthia, Miquel Lürling, Jutta Fastner, Lisette De Senerpont Domis, Elżbieta Wilk-Woźniak, Judita Koreivienė, Laura Seelen et al. "Temperature Effects Explain Continental Scale Distribution of Cyanobacterial Toxins". Toxins 10, n.º 4 (13 de abril de 2018): 156. http://dx.doi.org/10.3390/toxins10040156.
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Insight into how environmental change determines the production and distribution of cyanobacterial toxins is necessary for risk assessment. Management guidelines currently focus on hepatotoxins (microcystins). Increasing attention is given to other classes, such as neurotoxins (e.g., anatoxin-a) and cytotoxins (e.g., cylindrospermopsin) due to their potency. Most studies examine the relationship between individual toxin variants and environmental factors, such as nutrients, temperature and light. In summer 2015, we collected samples across Europe to investigate the effect of nutrient and temperature gradients on the variability of toxin production at a continental scale. Direct and indirect effects of temperature were the main drivers of the spatial distribution in the toxins produced by the cyanobacterial community, the toxin concentrations and toxin quota. Generalized linear models showed that a Toxin Diversity Index (TDI) increased with latitude, while it decreased with water stability. Increases in TDI were explained through a significant increase in toxin variants such as MC-YR, anatoxin and cylindrospermopsin, accompanied by a decreasing presence of MC-LR. While global warming continues, the direct and indirect effects of increased lake temperatures will drive changes in the distribution of cyanobacterial toxins in Europe, potentially promoting selection of a few highly toxic species or strains.
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Mueller, Elizabeth A., Joseph A. Merriman e Patrick M. Schlievert. "Toxic shock syndrome toxin-1, not α-toxin, mediated Bundaberg fatalities". Microbiology 161, n.º 12 (1 de dezembro de 2015): 2361–68. http://dx.doi.org/10.1099/mic.0.000196.
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Wu, Jing, Yu Zhou, Zhihang Yuan, Jine Yi, Jingshu Chen, Naidong Wang e Yanan Tian. "Autophagy and Apoptosis Interact to Modulate T-2 Toxin-Induced Toxicity in Liver Cells". Toxins 11, n.º 1 (15 de janeiro de 2019): 45. http://dx.doi.org/10.3390/toxins11010045.
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T-2 toxin is a mycotoxin generated by Fusarium species which has been shown to be highly toxic to human and animals. T-2 toxin induces apoptosis in various tissues/organs. Apoptosis and autophagy are two closely interconnected processes, which are important for maintaining physiological homeostasis as well as pathogenesis. Here, for the first time, we demonstrated that T-2 toxins induce autophagy in human liver cells (L02). We demonstrated that T-2 toxin induce acidic vesicular organelles formation, concomitant with the alterations in p62/SQSTM1 and LC3-phosphatidylethanolamine conjugate (LC3-II) and the enhancement of the autophagic flux. Using mRFP-GFP-LC3 by lentiviral transduction, we showed T-2 toxin-mediated lysosomal fusion and the formation of autophagosomes in L02 cells. The formation of autophagosomes was further confirmed by transmission electron microcopy. While T-2 toxin induced both autophagy and apoptosis, autophagy appears to be a leading event in the response to T-2 toxin treatment, reflecting its protective role in cells against cellular damage. Activating autophagy by rapamycin (RAPA) inhibited apoptosis, while suppressing autophagy by chloroquine greatly enhanced the T-2 toxin-induced apoptosis, suggesting the crosstalk between autophagy and apoptosis. Taken together, these results indicate that autophagy plays a role in protecting cells from T-2 toxin-induced apoptosis suggesting that autophagy may be manipulated for the alleviation of toxic responses induced by T-2 toxin.
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Thomas, Damien, Olivier Dauwalder, Virginie Brun, Cedric Badiou, Tristan Ferry, Jerome Etienne, François Vandenesch e Gerard Lina. "Staphylococcus aureus Superantigens Elicit Redundant and Extensive Human Vβ Patterns". Infection and Immunity 77, n.º 5 (2 de março de 2009): 2043–50. http://dx.doi.org/10.1128/iai.01388-08.
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ABSTRACT Staphylococcus aureus can produce a wide variety of exotoxins, including toxic shock syndrome toxin 1 (TSST-1), staphylococcal enterotoxins, and staphylococcal enterotoxin-like toxins. These toxins share superantigenic activity. To investigate the β chain (Vβ) specificities of each of these toxins, TSST-1 and all known S. aureus enterotoxins and enterotoxin-like toxins were produced as recombinant proteins and tested for their ability to induce the selective in vitro expansion of human T cells bearing particular Vβ T-cell receptors (TCR). Although redundancies were observed between the toxins and the Vβ populations, each toxin induced the expansion of distinct Vβ subsets, including enterotoxin H and enterotoxin-like toxin J. Surprisingly, the Vβ signatures were not associated with a specific phylogenic group of toxins. Interestingly, each human Vβ analyzed in this study was stimulated by at least one staphylococcal superantigen, suggesting that the bacterium derives a selective advantage from targeting the entire human TCR Vβ panel.
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Krishnan, Vidisha, Barbara Domanska, Alicia Elhigazi, Fatai Afolabi, Michelle J. West e Neil Crickmore. "The human cancer cell active toxin Cry41Aa from Bacillus thuringiensis acts like its insecticidal counterparts". Biochemical Journal 474, n.º 10 (28 de abril de 2017): 1591–602. http://dx.doi.org/10.1042/bcj20170122.
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Understanding how certain protein toxins from the normally insecticidal bacterium Bacillus thuringiensis (Bt) target human cell lines has implications for both the risk assessment of products containing these toxins and potentially for cancer therapy. This understanding requires knowledge of whether the human cell active toxins work by the same mechanism as their insecticidal counterparts or by alternative ones. The Bt Cry41Aa (also known as Parasporin3) toxin is structurally related to the toxins synthesised by commercially produced transgenic insect-resistant plants, with the notable exception of an additional C-terminal β-trefoil ricin domain. To better understand its mechanism of action, we developed an efficient expression system for the toxin and created mutations in regions potentially involved in the toxic mechanism. Deletion of the ricin domain did not significantly affect the activity of the toxin against the human HepG2 cell line, suggesting that this region was not responsible for the mammalian specificity of Cry41Aa. Various biochemical assays suggested that unlike some other human cell active toxins from Bt Cry41Aa did not induce apoptosis, but that its mechanism of action was consistent with that of a pore-forming toxin. The toxin induced a rapid and significant decrease in metabolic activity. Adenosine triphosphate depletion, cell swelling and membrane damage were also observed. An exposed loop region believed to be involved in receptor binding of insecticidal Cry toxins was shown to be important for the activity of Cry41Aa against HepG2 cells.
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Saenz, Jose B., Teresa A. Doggett e David B. Haslam. "Identification and Characterization of Small Molecules That Inhibit Intracellular Toxin Transport". Infection and Immunity 75, n.º 9 (18 de junho de 2007): 4552–61. http://dx.doi.org/10.1128/iai.00442-07.
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ABSTRACT Shiga toxin (Stx), cholera toxin (Ctx), and the plant toxin ricin are among several toxins that reach their intracellular destinations via a complex route. Following endocytosis, these toxins travel in a retrograde direction through the endosomal system to the trans-Golgi network, Golgi apparatus, and endoplasmic reticulum (ER). There the toxins are transported across the ER membrane to the cytosol, where they carry out their toxic effects. Transport via the ER from the cell surface to the cytosol is apparently unique to pathogenic toxins, raising the possibility that various stages in the transport pathway can be therapeutically targeted. We have applied a luciferase-based high-throughput screen to a chemical library of small-molecule compounds in order to identify inhibitors of Stx. We report two novel compounds that protect against Stx and ricin inhibition of protein synthesis, and we demonstrate that these compounds reversibly inhibit bacterial transport at various stages in the endocytic pathway. One compound (compound 75) inhibited transport at an early stage of Stx and Ctx transport and also provided protection against diphtheria toxin, which enters the cytosol from early endosomes. In contrast, compound 134 inhibited transport from recycling endosomes through the Golgi apparatus and protected only against toxins that access the ER. Small-molecule compounds such as these will provide insight into the mechanism of toxin transport and lead to the identification of compounds with therapeutic potential against toxins routed through the ER.
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Tse, Sirius Pui-kam, Fred Wang-fat Lee, Daniel Yun-lam Mak, Hang-kin Kong, Kenrick Kai-yuen Chan, Pak-yeung Lo e Samuel Chun-lap Lo. "Production of Paralytic Shellfish Toxins (PSTs) in Toxic Alexandrium catenella is Intertwined with Photosynthesis and Energy Production". Toxins 12, n.º 8 (27 de julho de 2020): 477. http://dx.doi.org/10.3390/toxins12080477.
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To investigate the mechanism for the production of paralytic shellfish toxins (PST) in toxic dinoflagellates, with a 2D-gel based approach, we had made two sets of proteomic comparisons: (a) between a toxic Alexandrium catenella (AC-T) and a phylogenetically closely related non-toxic strain (AC-N), (b) between toxic AC-T grown in a medium with 10% normal amount of phosphate (AC-T-10%P) known to induce higher toxicity and AC-T grown in normal medium. We found that photosynthesis and energy production related proteins were up-regulated in AC-T when compared to AC-N. However, the same group of proteins was down-regulated in AC-T-10%P when compared to normal AC-T. Examining the relationship of photosynthesis and toxin content of AC-T upon continuous photoperiod experiment revealed that while growth and associated toxin content increased after 8 days of continuous light, toxin content maintained constant when cells were shifted from continuous light to continuous dark for 3 days. This emphasized the cruciality of light availability on toxin biosynthesis in AC-T, while another light-independent mechanism may be responsible for higher toxicity in AC-T-10%P compared to normal AC-T. Taken all together, it is believed that the interplay between “illumination”, “photosynthesis”, “phosphate availability”, and “toxin production” is much more complicated than what we had previously anticipated.
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Singh, Sunita, e Prachi Lad. "Assay of Bacillus cereus Emetic toxin produced in orange squash". EUREKA: Life Sciences, n.º 2 (1 de abril de 2021): 41–55. http://dx.doi.org/10.21303/2504-5695.2021.001753.
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The contamination of squash by B. cereus, an enterotoxin producer, was found to range between 7.5×104 and 1.8×104 CFU/g in orange squash (during storage), that is hazardous. Orange squash is widely produced and consumed in India, but has a low rating of 3 on the scale of 10 (on feedback), mostly due to high sugars, not preferred these days. It can be preserved for >9 months due to added sugars and preservatives. During processing squash, if juice is not quickly cooled and/or squash is kept for long at temperatures <48 °C after processing, it can be a source of food poisoning. Reason, a large number of toxins can be produced by B. cereus. B. cereus strains, isolated from squash, produce heat stable toxin. Vacuolar assay confirmed them as emetic toxins, produced in squash. The toxin behaved like an ionophore in assay using mitochondria, extracted from liver cells of chicken with potassium ions in buffer. The toxicity of toxin by assay was 3200 IU/ng (BC IV strain) and 800 IU/ng (BC X strain). By the vacuolar expansions of mitochondria in assay, toxins of B. cereus demonstrated a toxic effect, in the range of 20.93 to 60.94 % by BC IV toxin and 43.28 to 45.02 % by BC X toxin, on the 3rd day growth of B. cereus in squash and toxin extraction for assay. It was also possible to produce antibodies against the B. cereus whole cell and toxin of BC IV, as an attempt to detect B. cereus contaminations in foods, by Ouchterlony’s immune-diffusion test
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Callahan, J. E., A. Herman, J. W. Kappler e P. Marrack. "Stimulation of B10.BR T cells with superantigenic staphylococcal toxins." Journal of Immunology 144, n.º 7 (1 de abril de 1990): 2473–79. http://dx.doi.org/10.4049/jimmunol.144.7.2473.
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Abstract The Staphylococcus aureus enterotoxins are known to be potent T cell activators, stimulating cell proliferation and lymphokine production. Two additional S. aureus proteins, exfoliating toxin and toxic shock syndrome toxin, share these properties. Recently these molecules have been termed "super-antigens" because of their ability to bind to class II MHC molecules and thus form ligands that interact with TCR in an unconventional manner. In this paper we show that each toxin stimulates mouse T cells bearing receptors that include particular V beta regions, almost regardless of the other variable receptor components. In addition, different toxins have different specificities for V beta.
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Mollick, J. A., M. Chintagumpala, R. G. Cook e R. R. Rich. "Staphylococcal exotoxin activation of T cells. Role of exotoxin-MHC class II binding affinity and class II isotype." Journal of Immunology 146, n.º 2 (15 de janeiro de 1991): 463–68. http://dx.doi.org/10.4049/jimmunol.146.2.463.
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Abstract Staphylococcal enterotoxins (SE) and toxic shock syndrome toxin-1 bind directly to class II molecules of the MHC and stimulate T cells based predominantly on the V beta segment used by the TCR. We investigated the relationship between the class II binding affinities of four of these exotoxins, SEA, SEB, SEC1, and toxic shock syndrome toxin-1 and their T cell signaling capabilities. Although the toxins stimulated T cells at concentrations that ranged over more than two orders of magnitude, their affinities for class II (DR1) differed by less than sixfold. The affinities of the toxins predicted their capacity to stimulate resting T cells to proliferate. The binding affinities of the toxins for class II molecules indicated that at concentrations required for T cell stimulation, as few as 0.1% of the class II molecules are complexed with toxin. Finally, the isotype of class II molecules affected the ability of the toxins to bind and use these MHC Ag to stimulate T cells. These data thus demonstrate that of the staphylococcal exotoxins studied, both their potency as T cell mitogens and their ability to function in the presence of single class II isotypes can be attributed in part to their characteristic abilities to bind class II molecules.
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Sánchez, Kristel F., Naomi Huntley, Meghan A. Duffy e Mark D. Hunter. "Toxins or medicines? Phytoplankton diets mediate host and parasite fitness in a freshwater system". Proceedings of the Royal Society B: Biological Sciences 286, n.º 1894 (16 de janeiro de 2019): 20182231. http://dx.doi.org/10.1098/rspb.2018.2231.
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Diets must satisfy the everyday metabolic requirements of organisms and can also serve as medicines to combat disease. Currently, the medicinal role of diets is much better understood in terrestrial than in aquatic ecosystems. This is surprising because phytoplankton species synthesize secondary metabolites with known antimicrobial properties. Here, we investigated the medicinal properties of phytoplankton (including toxin-producing cyanobacteria) against parasites of the dominant freshwater herbivore, Daphnia. We fed Daphnia dentifera on green algae and toxic cyanobacteria diets known to vary in their nutritional quality and toxin production, and an additional diet of Microcystis with added pure microcystin-LR. We then exposed Daphnia to fungal and bacterial parasites. Anabaena , Microcystis and Chlorella diets prevented infection of Daphnia by the fungal parasite Metschnikowia , while Nodularia toxins increased offspring production by infected hosts. In contrast to their medicinal effects against Metschnikowia , toxic phytoplankton generally decreased the fitness of Daphnia infected with the bacterial parasite, Pasteuria . We also measured the amount of toxin produced by phytoplankton over time. Concentrations of anatoxin-a produced by Anabaena increased in the presence of Metschnikowia , suggesting parasite-induced toxin production. Our research illustrates that phytoplankton can serve as toxins or medicines for their consumers, depending upon the identity of their parasites.
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Wagner, Nicole D., Felicia S. Osburn, Jingyu Wang, Raegyn B. Taylor, Ashlynn R. Boedecker, C. Kevin Chambliss, Bryan W. Brooks e J. Thad Scott. "Biological Stoichiometry Regulates Toxin Production in Microcystis aeruginosa (UTEX 2385)". Toxins 11, n.º 10 (16 de outubro de 2019): 601. http://dx.doi.org/10.3390/toxins11100601.
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Harmful algal blooms (HABs) are increasing in magnitude, frequency, and duration globally. Even though a limited number of phytoplankton species can be toxic, they are becoming one of the greatest water quality threats to public health and ecosystems due to their intrinsic toxicity to humans and the numerous interacting factors that undermine HAB forecasting. Here, we show that the carbon:nitrogen:phosphorus (C:N:P) stoichiometry of a common toxic phytoplankton species, Microcystis, regulates toxin quotas during blooms through a tradeoff between primary and secondary metabolism. Populations with optimal C:N (< 8) and C:P (< 200) cellular stoichiometry consistently produced more toxins than populations exhibiting stoichiometric plasticity. Phosphorus availability in water exerted a strong control on population biomass and C:P stoichiometry, but N availability exerted a stronger control on toxin quotas by regulating population biomass and C:N:P stoichiometry. Microcystin-LR, like many phytoplankton toxins, is an N-rich secondary metabolite with a C:N stoichiometry that is similar to the optimal growth stoichiometry of Microcystis. Thus, N availability relative to P and light provides a dual regulatory mechanism that controls both biomass production and cellular toxin synthesis. Overall, our results provide a quantitative framework for improving forecasting of toxin production during HABs and compelling support for water quality management that limit both N and P inputs from anthropogenic sources.
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Roderer, Daniel, Oliver Hofnagel, Roland Benz e Stefan Raunser. "Structure of a Tc holotoxin pore provides insights into the translocation mechanism". Proceedings of the National Academy of Sciences 116, n.º 46 (30 de outubro de 2019): 23083–90. http://dx.doi.org/10.1073/pnas.1909821116.
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Tc toxins are modular toxin systems of insect and human pathogenic bacteria. They are composed of a 1.4-MDa pentameric membrane translocator (TcA) and a 250-kDa cocoon (TcB and TcC) encapsulating the 30-kDa toxic enzyme (C terminus of TcC). Binding of Tc toxins to target cells and a pH shift trigger the conformational transition from the soluble prepore state to the membrane-embedded pore. Subsequently, the toxic enzyme is translocated and released into the cytoplasm. A high-resolution structure of a holotoxin embedded in membranes is missing, leaving open the question of whether TcB-TcC has an influence on the conformational transition of TcA. Here we show in atomic detail a fully assembled 1.7-MDa Tc holotoxin complex from Photorhabdus luminescens in the membrane. We find that the 5 TcA protomers conformationally adapt to fit around the cocoon during the prepore-to-pore transition. The architecture of the Tc toxin complex allows TcB-TcC to bind to an already membrane-embedded TcA pore to form a holotoxin. Importantly, assembly of the holotoxin at the membrane results in spontaneous translocation of the toxic enzyme, indicating that this process is not driven by a proton gradient or other energy source. Mammalian lipids with zwitterionic head groups are preferred over other lipids for the integration of Tc toxins. In a nontoxic Tc toxin variant, we can visualize part of the translocating toxic enzyme, which transiently interacts with alternating negative charges and hydrophobic stretches of the translocation channel, providing insights into the mechanism of action of Tc toxins.
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Contreras, Andrea M., Islay D. Marsden e Murray H. G. Munro. "Effects of short-term exposure to paralytic shellfish toxins on clearance rates and toxin uptake in five species of New Zealand bivalve". Marine and Freshwater Research 63, n.º 2 (2012): 166. http://dx.doi.org/10.1071/mf11173.
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Algal blooms produced by toxic dinoflagellates have increased worldwide, resulting in economic losses to aquaculture and fisheries. Bivalve species differ in their ability to feed on toxin-producing dinoflagellates and this could result in differences in toxin accumulation among species. In New Zealand, the effects of paralytic shellfish poisoning (PSP) toxins on the physiology of bivalve molluscs are relatively unknown. We hypothesised that the feeding responses of five New Zealand bivalve species exposed to PSP-toxic dinoflagellates would be species-specific, affecting their accumulation of toxins. Each species was exposed to toxic and non-toxic species of Alexandrium spp. and clearance rate used as an index of sensitivity to PSP toxins. Clearance rates for the mussel Perna canaliculus and the clam Dosinia anus were unaffected by the presence of toxic dinoflagellates, whereas the rate in the scallop Pecten novaezelandiae decreased significantly. There were variable results for the clam Paphies donacina and the oyster Ostrea chilensis. Species-specific biotransformation of PSP-toxins had taken place in the bivalve tissues. We conclude that the rate of accumulation of PSP toxins in the tissues of the bivalve species was influenced by their feeding behaviour and the different chemical processes that had taken place in their tissues.
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Blennerhassett, Ryann A., Kim Bell-Anderson, Richard Shine e Gregory P. Brown. "The cost of chemical defence: the impact of toxin depletion on growth and behaviour of cane toads ( Rhinella marina )". Proceedings of the Royal Society B: Biological Sciences 286, n.º 1902 (15 de maio de 2019): 20190867. http://dx.doi.org/10.1098/rspb.2019.0867.
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Many animals capable of deploying chemical defences are reluctant to use them, suggesting that synthesis of toxins imposes a substantial cost. Typically, such costs have been quantified by measuring the elevation in metabolic rate induced by toxin depletion (i.e. during replenishment of toxin stores). More generally, we might expect that toxin depletion will induce shifts in a broad suite of fitness-relevant traits. In cane toads ( Rhinella marina ), toxic compounds that protect against predators and pathogens are stored in large parotoid (shoulder) glands. We used correlational and experimental approaches in field and laboratory settings to investigate impacts of toxin depletion on growth rate and behaviour in cane toads. In free-ranging toads, larger toxin stores were associated with smaller gonads and livers, suggesting energetic trade-offs between toxin production and both reproduction and energy metabolism. Experimental removal of toxin (by manually squeezing parotoid glands) reduced rates of growth in body mass in both captive and free-ranging toads. Radio tracking demonstrated that de-toxined toads dispersed more slowly than did control toads. Given that toxin stores in cane toads take several months to fully replenish, deploying toxin to repel a predator may impose a substantial cost, explaining why toads use toxin only as a final line of defence.
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Bogati, Bikash, Selene F. H. Shore, Thomas D. Nipper, Oana Stoiculescu e Elizabeth M. Fozo. "Charged Amino Acids Contribute to ZorO Toxicity". Toxins 15, n.º 1 (31 de dezembro de 2022): 32. http://dx.doi.org/10.3390/toxins15010032.
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Chromosomally encoded toxin-antitoxin systems have been increasingly identified and characterized across bacterial species over the past two decades. Overproduction of the toxin gene results in cell growth stasis or death for the producing cell, but co-expression of its antitoxin can repress the toxic effects. For the subcategory of type I toxin-antitoxin systems, many of the described toxin genes encode a small, hydrophobic protein with several charged residues distributed across the sequence of the toxic protein. Though these charged residues are hypothesized to be critical for the toxic effects of the protein, they have not been studied broadly across different type I toxins. Herein, we mutated codons encoding charged residues in the type I toxin zorO, from the zor-orz toxin-antitoxin system, to determine their impacts on growth inhibition, membrane depolarization, ATP depletion, and the localization of this small protein. The non-toxic variants of ZorO accumulated both in the membrane and cytoplasm, indicating that membrane localization alone is not sufficient for its toxicity. While mutation of a charged residue could result in altered toxicity, this was dependent not only on the position of the amino acid within the protein but also on the residue to which it was converted, suggesting a complex role of charged residues in ZorO-mediated toxicity. A previous study indicated that additional copies of the zor-orz system improved growth in aminoglycosides: within, we note that this improved growth is independent of ZorO toxicity. By increasing the copy number of the zorO gene fused with a FLAG-tag, we were able to detect the protein expressed from its native promoter elements: an important step for future studies of toxin expression and function.
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Crass, B. A., e M. S. Bergdoll. "Toxin Involvement in Toxic Shock Syndrome". Journal of Infectious Diseases 153, n.º 5 (1 de maio de 1986): 918–26. http://dx.doi.org/10.1093/infdis/153.5.918.
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Jarraud, Sophie, Grégoire Cozon, François Vandenesch, Michèle Bes, Jerome Etienne e Gerard Lina. "Involvement of Enterotoxins G and I in Staphylococcal Toxic Shock Syndrome and Staphylococcal Scarlet Fever". Journal of Clinical Microbiology 37, n.º 8 (1999): 2446–49. http://dx.doi.org/10.1128/jcm.37.8.2446-2449.1999.
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We investigated the involvement of the recently described staphylococcal enterotoxins G and I in toxic shock syndrome. We reexamined Staphylococcus aureus strains isolated from patients with menstrual and nonmenstrual toxic shock syndrome (nine cases) or staphylococcal scarlet fever (three cases). These strains were selected because they produced none of the toxins known to be involved in these syndromes (toxic shock syndrome toxin 1 and enterotoxins A, B, C, and D), enterotoxin E or H, or exfoliative toxin A or B, despite the fact that superantigenic toxins were detected in a CD69-specific flow cytometry assay measuring T-cell activation. Sets of primers specific to the enterotoxin G and I genes (seg andsei, respectively) were designed and used for PCR amplification. All of the strains were positive for seg andsei. Sequence analysis confirmed that the PCR products, corresponded to the target genes. We suggest that staphylococcal enterotoxins G and I may be capable of causing human staphylococcal toxic shock syndrome and staphylococcal scarlet fever.
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Pitchenin, Leticia Camara, Laila Natasha Santos Brandão, Janaina Marcela Assunção Rosa, Francielle Cristina Kagueyama, Alvair da Silva Alves, Ícaro Sergio Magalães Rocha, Luciano Nakazato e Valéria Dutra. "Occurrence of toxin genes in Staphylococcus pseudintermedius from diseased dogs and other domestic and wild species". Journal of Infection in Developing Countries 11, n.º 12 (10 de janeiro de 2018): 957–61. http://dx.doi.org/10.3855/jidc.8261.
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Introduction: Staphylococcus pseudintermedius is coagulase-positive species of the Staphylococcus intermedius group. It is an opportunistic pathogen that can cause infection in various parts of the body and has a zoonotic potential. Although studies on the pathogenicity and epidemiology of S. pseudintermedius are limited, it is known that this bacterium has several virulence factors, including toxins. These toxins can be classified into three main groups: pyrogenic toxins with superantigenic properties such as toxic shock syndrome toxin and staphylococcal enterotoxins, exfoliative toxins, and cytotoxins such as hemolysins and leukocidins.
Methodology: In this study, the occurrence of eight toxin genes (sea, sec, tst, SIET, EXI, LuK F-I, Luk S-I, and hlg ƴ) was examined by PCR in 58 isolates of S. pseudintermedius from four domestic animal species.
Results: All S. pseudintermedius isolates had at least one of the eight toxin genes. The predominant toxin genes were Luk S-I (95%), Luk F-I (91%), and EXI (91%), and the least prevalent gene was hlg ƴ (5%). Significant association (p = 0.0175) was found between the occurrence patterns of genes hlg ƴ and Luk F-I.
Conclusions: The frequent occurrence of these genes in S. pseudintermedius obtained from diseased animals indicates that these toxins may play an important role in the pathogenesis of infection among domestic animals.
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Rourke, Wade A., e Cory J. Murphy. "Animal-Free Paralytic Shellfish Toxin Testing—The Canadian Perspective to Improved Health Protection". Journal of AOAC INTERNATIONAL 97, n.º 2 (1 de março de 2014): 334–38. http://dx.doi.org/10.5740/jaoacint.sgerourke.
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Abstract The performance characteristics of AOAC Official Method 2011.02 (the PCOX method) asa replacement for the AOAC mouse bioassay procedure have been well defined by validation studies, but these data do not communicate the complete story. Thecontext provided by analyzing 9000 regulatory monitoring samples over 3 years demonstrates not only the reduction in animal use but also the increase in foodsafety that has been realized using a chemistry-based method. Detection of lower toxin levels provided early warning to enable directed sampling as toxin levels increased. The toxin profile information generated by a chemistry-based method was used to detect potential interferences qualitatively and can be usedto assess the impact of changes recommended to monitoring programs. Such changes might include which toxins should be included in an action limit or the toxic equivalence factors used for these toxins.
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van Gils, Jan A., Matthijs van der Geest, Jutta Leyrer, Thomas Oudman, Tamar Lok, Jeroen Onrust, Jimmy de Fouw et al. "Toxin constraint explains diet choice, survival and population dynamics in a molluscivore shorebird". Proceedings of the Royal Society B: Biological Sciences 280, n.º 1763 (22 de julho de 2013): 20130861. http://dx.doi.org/10.1098/rspb.2013.0861.
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Recent insights suggest that predators should include (mildly) toxic prey when non-toxic food is scarce. However, the assumption that toxic prey is energetically as profitable as non-toxic prey misses the possibility that non-toxic prey have other ways to avoid being eaten, such as the formation of an indigestible armature. In that case, predators face a trade-off between avoiding toxins and minimizing indigestible ballast intake. Here, we report on the trophic interactions between a shorebird (red knot, Calidris canutus canutus ) and its two main bivalve prey, one being mildly toxic but easily digestible, and the other being non-toxic but harder to digest. A novel toxin-based optimal diet model is developed and tested against an existing one that ignores toxin constraints on the basis of data on prey abundance, diet choice, local survival and numbers of red knots at Banc d'Arguin (Mauritania) over 8 years. Observed diet and annual survival rates closely fit the predictions of the toxin-based model, with survival and population size being highest in years when the non-toxic prey is abundant. In the 6 of 8 years when the non-toxic prey is not abundant enough to satisfy the energy requirements, red knots must rely on the toxic alternative.
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Courçon, Marie, Cédric Badiou, Mathilde Louwagie, Sibyle Etievant, Michel Jaquinod, Gérard Lina e Virginie Brun. "Targeted Proteomics Analysis of Staphylococcal Superantigenic Toxins in Menstrual Fluid from Women with Menstrual Toxic Shock Syndrome (mTSS)". Toxins 14, n.º 12 (19 de dezembro de 2022): 886. http://dx.doi.org/10.3390/toxins14120886.
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Menstrual toxic shock syndrome (mTSS) is a rare life-threatening febrile illness that occurs in women using intravaginal menstrual protection. It is caused by toxic shock syndrome toxin 1 (TSST-1) produced by Staphylococcus aureus, triggering a sudden onset of rash and hypotension, subsequently leading to multiple organ failure. Detecting TSST-1 and S. aureus virulence factors in menstrual fluid could accelerate the diagnosis and improve therapeutic management of mTSS. However, menstrual fluid is a highly complex matrix, making detection of bacterial toxins challenging. Here, we present a mass-spectrometry-based proteomics workflow for the targeted, quantitative analysis of four S. aureus superantigenic toxins in menstrual fluids (TSST-1, SEA, SEC, and SED). This method was applied to characterize toxin levels in menstrual fluids collected from patients with mTSS and healthy women. Toxins were detectable in samples from patients with mTSS and one healthy donor at concentrations ranging from 0 to 0.46 µg/mL for TSST-1, and 0 to 1.07 µg/mL for SEC. SEA and SED were never detected in clinical specimens, even though many S. aureus strains were positive for the corresponding genes. The method presented here could be used to explore toxin production in vivo in users of intravaginal devices to improve the diagnosis, understanding, and prevention of mTSS.
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Rotaru, Lilia. "Environmental toxic factors and clinical pattern of Parkinson’s disease". Moldovan Medical Journal 64, n.º 4 (outubro de 2021): 69–71. http://dx.doi.org/10.52418/moldovan-med-j.64-4.21.13.
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Background: Parkinson’s disease (PD) – the most common neuro-degenerative movement disorder – is considered a result of a multifactorial pathogenic process modulated by cumulative and interactive effects of genes and exposures. An environmental exposure could enhance or create dopaminergic neurons vulnerability and increase PD risk. The purpose of the study was to find if excessive exposure to toxic environmental factors may influence clinical pattern of PD. Material and methods: The study was conducted on 111 patients diagnosed with PD, study group being defined as PD exposed to toxins (33 patients), control group including PD patients without toxin exposure (78 patients). General epidemiological data and clinical data were recorded. Results: Toxin exposure was found in 33 patients (29.73%), more of them – men and rural residents. Toxin exposed PD patients had an insignificantly younger age. The most common disease phenotype in the study group was the akinetic-rigid phenotype (64.7%, p = 0.040), bradykinesia being the most common sign at the disease onset (57.6%, p = 0.008). Levodopa equivalent daily dose also was higher in the study group (659.02 ± 232.46, p = 0.042). Conclusions: Excessive exposure to toxic environmental factors may influence the clinical pattern of PD. In this study the akinetic-rigid type was the predominant disease phenotype associated with toxin exposure. Doses needed for treatment were higher in PD patients exposed to toxins, as an indicator of a more severe motor impairment in this group
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Upadhyay, R. K., R. K. Naji e N. Kumari. "Dynamical Complexity in Some Ecological Models: Effects of Toxin Production by Phytoplankton". Nonlinear Analysis: Modelling and Control 12, n.º 1 (25 de janeiro de 2007): 123–38. http://dx.doi.org/10.15388/na.2007.12.1.14726.
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We investigate dynamical complexities in two types of chaotic tri-trophic aquatic food-chain model systems representing a real situation in the marine environment. Phytoplankton produce chemical substances known as toxins to reduce grazing pressure by zooplankton [1]. The role of toxin producing phytoplankton (TPP) on the chaotic behavior in these food chain systems is investigated. Holling type I, II, and III functional response forms are considered to study the interference between phytoplankton and zooplankton populations in the presence of toxic chemical. Our study shows that chaotic dynamics is robust to changes in the rates of toxin release as well as the toxin release functions. The present study also reveals that the rate of toxin production by toxin producing phytoplankton plays an important role in controlling oscillations in the plankton system. The different mortality functions of zooplankton due to toxin producing phytoplankton have significant influence in controlling oscillations, coexistence, survival or extinction of the zooplankton population. Further studies are needed to ascertain if this defence mechanism suppresses chaotic dynamics in model aquatic systems.
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McNichol, Beth A., Rebecca A. Bova, Kieron Torres, Lan N. Preston e Angela R. Melton-Celsa. "Switching Shiga Toxin (Stx) Type from Stx2d to Stx2a but Not Stx2c Alters Virulence of Stx-Producing Escherichia coli (STEC) Strain B2F1 in Streptomycin (Str)-Treated Mice". Toxins 13, n.º 1 (15 de janeiro de 2021): 64. http://dx.doi.org/10.3390/toxins13010064.
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Shiga toxin (Stx)-producing Escherichia coli (STEC) strain B2F1 produces Stx type 2d, a toxin that becomes more toxic towards Vero cells in the presence of intestinal mucus. STEC that make Stx2d are more pathogenic to streptomycin (Str)-treated mice than most STEC that produce Stx2a or Stx2c. However, purified Stx2d is only 2- or 7-fold more toxic by the intraperitoneal route than Stx2a or Stx2c, respectively. We hypothesized, therefore, that the toxicity differences among Stx2a, Stx2c, and Stx2d occur at the level of delivery from the intestine. To evaluate that hypothesis, we altered the toxin type produced by stx2d+ mouse virulent O91:H21 clinical isolate B2F1 to Stx2a or Stx2c. Because B2F1 encodes two copies of stx2d, we did these studies in a derivative of B2F1 in which stx2d1 was deleted. Although the strains were equivalently virulent to the Str-treated mice at the 1010 dose, the B2F1 strain that produced Stx2a was attenuated relative to the ones that produced Stx2d or Stx2c when administered at 103 CFU/mouse. We next compared the oral toxicities of purified Stx2a, Stx2c, and Stx2d. We found that purified Stx2d is more toxic than Stx2a or Stx2c upon oral administration at 4 µg/mouse. Taken together, these studies suggest that Stx2 toxins are most potent when delivered directly from the bacterium. Furthermore, because Stx2d and Stx2c have the identical amino acid composition in the toxin B subunit, our results indicate that the virulence difference between Stx2a and Stx2d and Stx2c resides in the B or binding subunit of the toxins.
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Griffiths, S. L., R. A. Finkelstein e D. R. Critchley. "Characterization of the receptor for cholera toxin and Escherichia coli heat-labile toxin in rabbit intestinal brush borders". Biochemical Journal 238, n.º 2 (1 de setembro de 1986): 313–22. http://dx.doi.org/10.1042/bj2380313.
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125I-labelled heat-labile toxin (from Escherichia coli) and 125I-labelled cholera toxin bound to immobilized ganglioside GM1 and Balb/c 3T3 cell membranes with identical specificities, i.e. each toxin inhibited binding of the other. Binding of both toxins to Balb/c 3T3 cell membranes was saturable, with 50% of maximal binding occurring at 0.3 nM for cholera toxin and 1.1 nM for heat-labile toxin, and the number of sites for each toxin was similar. The results suggest that both toxins recognize the same receptor, namely ganglioside GM1. In contrast, binding of 125I-heat-labile toxin to rabbit intestinal brush borders at 0 degree C was not inhibited by cholera toxin, although heat-labile toxin inhibited 125I-cholera toxin binding. In addition, there were 3-10-fold more binding sites for heat-labile toxin than for cholera toxin. At 37 degrees C cholera toxin, but more particularly its B-subunit, did significantly inhibit 125I-heat-labile toxin binding. Binding of 125I-cholera toxin was saturable, with 50% maximal of binding occurring at 1-2 nM, and was quantitatively inhibited by 10(-8) M unlabelled toxin or B-subunit. By contrast, binding of 125I-heat-labile toxin was non-saturable (up to 5 nM), and 2 × 10(-7) M unlabelled B-subunit was required to quantitatively inhibit binding. Neuraminidase treatment of brush borders increased 125I-cholera toxin but not heat-labile toxin binding. Extensive digestion of membranes with Streptomyces griseus proteinase or papain did not decrease the binding of either toxin. The additional binding sites for heat-labile toxin are not gangliosides. Thin-layer chromatograms of gangliosides which were overlayed with 125I-labelled toxins showed that binding of both toxins was largely restricted to ganglioside GM1. However, 125I-heat-labile toxin was able to bind to brush-border galactoproteins resolved by SDS/polyacrylamide-gel electrophoresis and transferred to nitrocellulose.
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Kormas, Konstantinos Ar, e Despoina S. Lymperopoulou. "Cyanobacterial Toxin Degrading Bacteria: Who Are They?" BioMed Research International 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/463894.
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Cyanobacteria are ubiquitous in nature and are both beneficial and detrimental to humans. Benefits include being food supplements and producing bioactive compounds, like antimicrobial and anticancer substances, while their detrimental effects are evident by toxin production, causing major ecological problems at the ecosystem level. To date, there are several ways to degrade or transform these toxins by chemical methods, while the biodegradation of these compounds is understudied. In this paper, we present a meta-analysis of the currently available 16S rRNA andmlrA(microcystinase) genes diversity of isolates known to degrade cyanobacterial toxins. The available data revealed that these bacteria belong primarily to the Proteobacteria, with several strains from the sphingomonads, and one from each of theMethylobacillusandPaucibactergenera. Other strains belonged to the generaArthrobacter, Bacillus, andLactobacillus. By combining the ecological knowledge on the distribution, abundance, and ecophysiology of the bacteria that cooccur with toxic cyanobacterial blooms and newly developed molecular approaches, it is possible not only to discover more strains with cyanobacterial toxin degradation abilities, but also to reveal the genes associated with the degradation of these toxins.
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Roberts, Lynne, e Daniel Smith. "Targeting toxins!: Drug delivery with poisons". Biochemist 24, n.º 1 (1 de fevereiro de 2002): 18–20. http://dx.doi.org/10.1042/bio02401018.
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Many organisms produce potently toxic proteins that act on other cells, sometimes with lethal effects. In this way, such proteins help to increase the chance of survival or proliferation of the producing organism. Moreover, a lot of toxins have an exquisitely specific action. For example, proteins studied in the Warwick toxin laboratory -- ricin, a toxin from the castor oil seed (Figure 1), and its relatives from the pathogenic Escherichia coli 0157 and the dysentery-causing bacterium (Shigella dysenteriae), have evolved to selectively target ribosomes within the cells of susceptible organisms, thereby enabling a fatal disruption of protein synthesis. What is very striking is the clever way these particular toxins exploit intracellular transport pathways to travel from the cell surface to their substrates in the cytosol. Once delivered there, each toxin molecule can disable approximately 2000 polysomes per minute, enough to eventually kill the cell. Research is now aimed at elucidating the molecular details of the cellular uptake of ricin and the Shiga family of toxins, and of exploiting their unusual trafficking properties for biotechnological purposes.
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Kirby, James E. "Anthrax Lethal Toxin Induces Human Endothelial Cell Apoptosis". Infection and Immunity 72, n.º 1 (janeiro de 2004): 430–39. http://dx.doi.org/10.1128/iai.72.1.430-439.2004.
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ABSTRACT Because of its ease of dispersal and high lethality, Bacillus anthracis is one of the most feared biowarfare agents. A better understanding of anthrax pathogenesis is urgently needed to develop new therapies for systemic disease that is relatively unresponsive to antibiotics. Although experimental evidence has implicated a role for macrophages in anthrax pathogenesis, clinical and pathological observations suggest that a direct insult to the host vasculature may also be important. Two bacterial toxins, lethal toxin and edema toxin, are believed to mediate the clinical sequelae of anthrax. Here, I examined whether these toxins are directly toxic to endothelial cells, the cell type that lines the interior of blood vessels. I show for the first time that lethal toxin but not edema toxin reduces the viability of cultured human endothelial cells and induces caspase-dependent endothelial apoptosis. In addition, this toxicity affects both microvascular and large vessel endothelial cells as well as endothelial cells that have differentiated into tubules within a type I collagen extracellular matrix. Finally, lethal toxin induces cleavage of mitogen-activated protein kinase kinases in endothelial cells and inhibits phosphorylation of ERK, p38, and JNK p46. Based on the contributions of these pathways to endothelial survival, I propose that lethal toxin-mediated cytotoxicity/apoptosis results primarily through inhibition of the ERK pathway. I also hypothesize that the observed endothelial toxicity contributes to vascular pathology and hemorrhage during systemic anthrax.