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"Toxins"
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Toxic histories : poison and pollution in modern India
\"Toxic Histories combines social, scientific, medical and environmental history to demonstrate the critical importance of poison and pollution to colonial governance, scientific authority and public anxiety in India between the 1830s and 1950s. Against the background of India's 'poison culture' and periodic 'poison panics', David Arnold considers why many familiar substances came to be regarded under colonialism as dangerous poisons. As well as the criminal uses of poison, Toxic Histories shows how European and Indian scientists were instrumental in creating a distinctive system of forensic toxicology and medical jurisprudence designed for Indian needs and conditions, and how local as well as universal poison knowledge could serve constructive scientific and medical purposes. Arnold reflects on how the 'fear of a poisoned world' spilt over into concerns about contamination and pollution, giving ideas of toxicity a wider social and political significance that has continued into India's postcolonial era\"-- Provided by publisher.
Book
On the chemistry, toxicology and genetics of the cyanobacterial toxins, microcystin, nodularin, saxitoxin and cylindrospermopsin
The cyanobacteria or \"blue-green algae\", as they are commonly termed, comprise a diverse group of oxygenic photosynthetic bacteria that inhabit a wide range of aquatic and terrestrial environments, and display incredible morphological diversity. Many aquatic, bloom-forming species of cyanobacteria are capable of producing biologically active secondary metabolites, which are highly toxic to humans and other animals. From a toxicological viewpoint, the cyanotoxins span four major classes: the neurotoxins, hepatotoxins, cytotoxins, and dermatoxins (irritant toxins). However, structurally they are quite diverse. Over the past decade, the biosynthesis pathways of the four major cyanotoxins: microcystin, nodularin, saxitoxin and cylindrospermopsin, have been genetically and biochemically elucidated. This review provides an overview of these biosynthesis pathways and additionally summarizes the chemistry and toxicology of these remarkable secondary metabolites.
Journal Article
An interbacterial toxin inhibits target cell growth by synthesizing (p)ppApp
Bacteria have evolved sophisticated mechanisms to inhibit the growth of competitors
. One such mechanism involves type VI secretion systems, which bacteria can use to inject antibacterial toxins directly into neighbouring cells. Many of these toxins target the integrity of the cell envelope, but the full range of growth inhibitory mechanisms remains unknown
. Here we identify a type VI secretion effector, Tas1, in the opportunistic pathogen Pseudomonas aeruginosa. The crystal structure of Tas1 shows that it is similar to enzymes that synthesize (p)ppGpp, a broadly conserved signalling molecule in bacteria that modulates cell growth rate, particularly in response to nutritional stress
. However, Tas1 does not synthesize (p)ppGpp; instead, it pyrophosphorylates adenosine nucleotides to produce (p)ppApp at rates of nearly 180,000 molecules per minute. Consequently, the delivery of Tas1 into competitor cells drives rapid accumulation of (p)ppApp, depletion of ATP, and widespread dysregulation of essential metabolic pathways, thereby resulting in target cell death. Our findings reveal a previously undescribed mechanism for interbacterial antagonism and demonstrate a physiological role for the metabolite (p)ppApp in bacteria.
Journal Article
The role of toxins in Clostridium difficile infection
Abstract
Clostridium difficile is a bacterial pathogen that is the leading cause of nosocomial antibiotic-associated diarrhea and pseudomembranous colitis worldwide. The incidence, severity, mortality and healthcare costs associated with C. difficile infection (CDI) are rising, making C. difficile a major threat to public health. Traditional treatments for CDI involve use of antibiotics such as metronidazole and vancomycin, but disease recurrence occurs in about 30% of patients, highlighting the need for new therapies. The pathogenesis of C. difficile is primarily mediated by the actions of two large clostridial glucosylating toxins, toxin A (TcdA) and toxin B (TcdB). Some strains produce a third toxin, the binary toxin C. difficile transferase, which can also contribute to C. difficile virulence and disease. These toxins act on the colonic epithelium and immune cells and induce a complex cascade of cellular events that result in fluid secretion, inflammation and tissue damage, which are the hallmark features of the disease. In this review, we summarize our current understanding of the structure and mechanism of action of the C. difficile toxins and their role in disease.
This review summarizes the structures, molecular mechanisms and physiological responses to the three toxins associated with disease symptoms in Clostridium difficile infection.
Journal Article
The toxin solution : how hidden poisons in the air, water, food, and products we use are destroying our health--and what we can do to fix it
\"Eliminate avoidable toxins, mitigate the effects of those you can't avoid, and enjoy a longer life with this ... health guide from a pioneer in integrative medicine, Dr. Joe Pizzorno--the author, teacher, practitioner, and founder of Bastyr University, the country's first and largest fully accredited university of natural medicine\"-- Provided by publisher.
Book
A bacterial cytidine deaminase toxin enables CRISPR-free mitochondrial base editing
Bacterial toxins represent a vast reservoir of biochemical diversity that can be repurposed for biomedical applications. Such proteins include a group of predicted interbacterial toxins of the deaminase superfamily, members of which have found application in gene-editing techniques
. Because previously described cytidine deaminases operate on single-stranded nucleic acids
, their use in base editing requires the unwinding of double-stranded DNA (dsDNA)-for example by a CRISPR-Cas9 system. Base editing within mitochondrial DNA (mtDNA), however, has thus far been hindered by challenges associated with the delivery of guide RNA into the mitochondria
. As a consequence, manipulation of mtDNA to date has been limited to the targeted destruction of the mitochondrial genome by designer nucleases
.Here we describe an interbacterial toxin, which we name DddA, that catalyses the deamination of cytidines within dsDNA. We engineered split-DddA halves that are non-toxic and inactive until brought together on target DNA by adjacently bound programmable DNA-binding proteins. Fusions of the split-DddA halves, transcription activator-like effector array proteins, and a uracil glycosylase inhibitor resulted in RNA-free DddA-derived cytosine base editors (DdCBEs) that catalyse C•G-to-T•A conversions in human mtDNA with high target specificity and product purity. We used DdCBEs to model a disease-associated mtDNA mutation in human cells, resulting in changes in respiration rates and oxidative phosphorylation. CRISPR-free DdCBEs enable the precise manipulation of mtDNA, rather than the elimination of mtDNA copies that results from its cleavage by targeted nucleases, with broad implications for the study and potential treatment of mitochondrial disorders.
Journal Article