ThesisPDF Available

THE MECHANISMS OF ARSENIC DETOXIFICATION BY THE GREEN MICROALGAE CHLORELLA VULGARIS

Authors:

Abstract and Figures

The mechanisms of arsenic interaction with the green microalga Chlorella vulgaris (C. vulgaris) and the potential for its bio-remediation from water were investigated. This was made possible by the development of an improved arsenic extraction from C. vulgaris, leading to successful glutathione and phytochelatins (GSH/PC) complex speciation analysis with 71.1% efficiency. The response of C. vulgaris when challenged by As(III), As(V) and dimethylarsinic acid (DMA) was assessed through experiments on adsorption, efflux and speciation of arsenic (reduction, oxidation, methylation and chelation with GSH/PC). At high phosphate concentration (1.62 mM of PO 4-3), poor adsorption of As(V) led to low intracellular uptake; at low phosphate concentration (3.2 µM of PO 4-3), an increase in the level of free thiols was observed as well as a moderate decrease in intracellular pH with no evidence for signals of oxidative stress. Chlorella vulgaris cells did not produce any As-GS/PC complex when exposed to As(V). This may indicate that a reduction step is needed for As(V) complexation with GSH/PC. Chlorella vulgaris cells formed DMAS V-GS upon exposure to DMA. The formation of this complex in vivo has only been reported once in Brassica oleracea plants. This complex is perhaps a fragment of a bigger molecule and thus part of another detoxification mechanism since its formation was not related to the concentration of DMA in media or the exposure time. It was found that As(III) triggers the formation of arsenic complexes with PC and homophytochelatins (hPC) and their compartmentalisation to vacuoles. It is the first time that, as a result of the newly developed extraction method using sonication, such intact complexes have been identified in C. vulgaris exposed to arsenic and their hPC complexes have been reported in any organism. The potential of C. vulgaris to bio-remediate arsenic from water is highly selective and effective for the more toxic As(III) (for human life) without the potential hazard to reduce As(V) to As(III). This was possible to assess because of the following empirical observations: At low phosphate (3.2 µM of PO 4-3) and in the presence of As(V), C. vulgaris are not likely to grow and be efficient at bio-remediating arsenic. At high phosphate (1.62 mM of PO 4-3) and in the presence of As(V), C. vulgaris are highly likely to grow but are not likely to be efficient at bio-remediating arsenic. However the potential to transform As(V) into more toxic As(III) is very low. Under any phosphate concentration and in the presence of As(III), C. vulgaris has high potential to bio-remediate arsenic, by storing As(III) into the cell biomass while retaining significantly high growth rates. ii
Content may be subject to copyright.
A preview of the PDF is not available
... The percentage of growth inhibition was calculated with reference to the control by the equation: % of growth inhibition= (1-μ2/μ1) ×100%, where μ2 and μ1 represent the growth rate at a certain Cd concentration and in the absence of Cd, respectively. The inhibition concentration to fifty percent of population (IC50, 96h=138 μmol L -1 ) of Cd was plotted by linear interpolation (referred to Munoz, 2014). ...
Article
Cadmium (Cd) pollution is a widespread threat to marine life, and ongoing ocean acidification (OA) is predicted to impact bio-toxicity of Cd compounds. However, the cascading effects of changed Cd toxicity to marine primary producers are not well characterized. Here, we studied the impact of OA on Cd toxicity responses in a globally important diatom Phaeodactylum tricornutum under both ambient and elevated pCO2 conditions. We found that increased pCO2 alleviated the impact of additive Cd toxicity on P. tricornutum not only under controlled indoor experiments but also in outdoor mesocosm experiments that reflect more natural growth conditions. Transcriptome analysis suggested that genes involved in Cd efflux and phytochelatin production were up-regulated and genes involved in Cd influx were down-regulated in long-term selected lineages under elevated pCO2. We further found a significant reduction of Cd transfer across trophic level, when the scallop Argopecten irradians was fed with Cd-exposed P. tricornutum previously cultured under elevated pCO2. Our results indicate that after long-term selection of P. tricornutum exposed to future OA conditions (i.e. elevated pCO2), the diatom alters its Cd detoxification strategy, which could have broader impacts on the bio-geochemical cycle of Cd in the marine ecosystem.
... This probe is largely used in plant field, both in flow cytometry and confocal microscopy studies (Vivancos et al. 2010;De Simone et al. 2015;Munoz et al. 2016). In particular, Munoz (2014) and Munoz et al. (2016) used this probe coupled to flow cytometry on the microalga Chlorella vulgaris to understand the mechanisms of detoxification of various forms of arsenic and dimethylarsenic acid. ...
Chapter
A variety of physiological parameters involved in signal transduction pathways, enzymatic activities, ATP production, and many other physiological processes can be analyzed by flow cytometry. Parameters as intracellular pH, membrane potential, calcium concentration, reactive oxygen species (ROS) generation, or glutathione content can be estimated thanks to this technique. One of the principal advantages of flow cytometry is that it allows the measurement of these parameters in living and small cells, usually in real time during the physiological stimulation. Moreover, flow cytometry can detect not only the fluorescence of biochemically specific developed fluorescent dyes but also autofluorescence (such as the chlorophyll a fluorescence), which can be measured in parallel and can provide supplementary information about the physiological condition of the measured cells.
... However, PC synthesis in D. salina induced by As(III) or As(V) was consistently lower than that in D. tertiolecta induced by Zn and Cd (0.5-1 μmol g −1 DW) (Hirata et al., 2001;Tsuji et al., 2002). PC synthesis induced by metal ions is in the following order: Cd 2+ , Hg 2+ , As 3+ , AsO 2 − , Cu 2+ , Zn 2+ , Pb + , AsO 4 3− , Mg 2+ , Ni 2+ and SeO 4 2− (Pantoja Munoz, 2014;Simmons and Emery, 2011;Vatamaniuk et al., 2000). However, this is not always true because of differences between algal species. ...
Chapter
Life in extreme and adverse environments has attracted significant interest in recent times. Researchers have found many microorganisms that thrive in these chemical and physical extremes that are hostile to most living organisms on our planet. An example of these extremophiles is Acidomyces acidophilus. Fungi within the genus Acidomyces are acidophilic and are highly adaptable to extremely acidic and toxic ecosystems. In this chapter, we will review how A. acidophilus has evolved to tolerate and survive under extreme conditions by adapting their metabolic functions and adopting different coping mechanisms. The review focuses on its ecology, biochemical properties and application to bioremediation based on the current knowledge. It seeks to provide important insight into this remarkable fungus and explore its role in biotechnological applications in extreme environments.
Chapter
Arsenic (As) pollution is a significant environmental problem. In nature, As exists as inorganic or organic species but is normally not encountered in its elemental state. As is a nonessential metalloid and does not play any biological role in algae, plants and causes toxic response after gaining entry into the cell. Upon translocation to the shoots As can severely impede growth of the plants by slowing or arresting accumulation of biomass, as well as induce loss of fertility, yield, and fruit production. Several reports are there indicating that an elevated concentration of As in soil causes a significant reduction in crop yield. Algae and plants have developed a range of strategies to combat As toxicity including chelation and sub-sequestration of complexes in vacuole. As contamination in human occurs through consumption of cereals, vegetables, and fruits irrigated with As-contaminated water. The consequence is a global epidemic of As poisoning, leading to skin lesion, cancer of bladder, lung, and kidney and other symptoms. Remediation of As-contaminated soil and groundwater, therefore, is an urgent need for providing safe drinking water and food. Among the various bioremediation processes, phytoremediation by algae and plants is quite effective. Phytoremediation strategy involves suitable plants including arsenic hyperaccumulating ferns and some aquatic or terrestrial angiosperms that efficiently remove the metalloid from highly contaminated soil/water. Utilization of transgenic plants is becoming a new promising tool to enhance phytoremediation potential. There is an urgency to have extensive knowledge on arsenic uptake, transport, metabolism, and detoxification in algae as well as plants for improving phytoremediation. The objective of this review is, therefore, to provide an overview about the uptake of the inorganic and organic species of arsenic, their translocation and biochemical fate in algae and plants and to explore the current concepts of phytoremediation along with their limitations and challenges associated with the developed processes.
Article
Full-text available
Arsenic is a toxic metalloid and its pollution has become a global environmental problem. This paper reviewed the current knowledge on the speciation, toxicity and metabolism of arsenic in microalgae. A number of arsenic species are present in various microalgae. Due to the great toxicity of inorganic arsenic, microalgae may undergo different processes to reduce the arsenic toxicity, including cell surface binding, arsenite [As(III)] oxidation, arsenate [As(V)] reduction, methylation, transformation into arsenosugars or arsenolipids, chelation of As(III) with glutathione and phytochelatins, as well as excretion from cells. Several genes and enzymes involved in arsenic transformations have been identified and characterized. Many factors, especially nutrient elements (e.g., nitrogen and phosphorus) in cells and in culture, affect arsenic metabolic pathways of microalgae. Arsenic metabolism in the unicellular algae has gained considerable interest because these processes control not only the effectiveness of arsenic phycoremediation, but also the risk of arsenic contamination in algal products. Future research need to focus on (1) the regulative mechanisms of arsenic absorption, biotransformation and excretion at molecular level; (2) the effects of intracellular nutrient dynamics on arsenic speciation; (3) the impacts of culture regime on the arsenic metabolism in microalgae; (4) the transfer of arsenic species across aquatic food web in order to better evaluate the roles of microalgae in arsenic cycling.
Book
This title includes a number of Open Access chapters.Environmental chemistry is an interdisciplinary field of study that involves the science of ecology as well as chemistry. Environmental chemistry covers the basic chemistry and biochemistry that occur naturally in the world around us. It focuses on the air, water, and land. Environmental science.
Book
Sixteen years have passed since human aquaporin-1 (AQP1) was discovered as the first water channel, facilitating trans-membrane water fluxes. Subsequent years of research showed that the water channel AQP1 was only the tip of an iceberg; the iceberg itself being the ubiquitous super family of membrane intrinsic proteins (MIPs) that facilitate trans-membrane transport of water and an increasing number of small, water-soluble and uncharged compounds. Here we introduce you to the superfamily of MIPs and provide a summary about our gradually refined understanding of the phylogenetic relationship of its members. This volume is dedicated to the metalloids, a recently discovered group of substrates for a number of specific MIPs in a diverse spectrum of organisms. Particular focus is given to the essential boron, the beneficial silicon and the highly toxic arsenic. The respective MIP isoforms that facilitate the transport of these metalloids include members from several clades of the phylogenetic tree, suggesting that metalloid transport is an ancient function within this family of channel proteins. Among all the various substrates that have been shown to be transported by MIPs, metalloids take an outstanding position. While water transport seems to be a common function of many MIPs, single isoforms in plants have been identified as being crucially important for the uptake of boric acid as well as silicic acid. Here, the function seems not to be redundant, as mutations in those genes render plants deficient in boron and silicon, respectively.
Article
Contents Preface...v Contributors...xi Analysis Of Protein Phosphatases: Toolbox For Unraveling Cell Signaling Networks. Shirish Shenolikar...X A Brief Introduction To The Protein Phosphatase Families. Tomas Mustelin...X Small Molecule Inhibitors of Ser/thr Protein Phosphatases: Specificity, Use and Common Forms of Abuse. Mark Swingle, Li Ni and Richard E. Honkanen...X Synthesis and Use of the Protein Phosphatase Affinity Matrices Microcystin- and Microcystin-biotin-Sepharose Greg Moorhead, Timothy AJ Haystead and Carol MacKintosh...X Utilizing Protein Phosphatase Inhibitors To Define PP2A As A Regulator Of Ataxia-Telangiectasia Mutated (ATM). Aaron A. Goodarzi, Pauline Douglas, Greg B.G. Moorhead and Susan P. Lees-Miller...X An Automated, Fluorescence-Based Method For Continuous Assay Of PP2A Activity. Adam M. Wegner, Jamie L. McConnell, Randy D. Blakely, and Brian E. Wadzinski...X An In Vivo Assay To Quantify Stable Protein Phosphatase 2A (PP2A) Heterotrimeric Species. Matthew S. Gentry, Richard L. Hallberg, and David C. Pallas...X Mutagenesis And Expression Of The Scaffolding AaAnd Ab Subunits Of PP2A Assays For Measuring Defects In Binding Of Cancer-Related Aa And Ab Mutants To The Regulatory B And Catalytic C Subunits. Ralf Ruediger, Jin Zhou, and Gernot Walter...X Isolation and Characterization of PP2A Holoenzymes Containing FLAG-tagged B Subunits. Deanna G. Adams and Brian E. Wadzinski...X Purification Of PP2A Holoenzymes By Sequential Immunoprecipitation With Anti-Peptide Antibodies. Gernot Walter, Jin Zhou, and Ralf Ruediger...X Purification Of PP2Ac From Bovine Heart. Hue T Tran, Tony S Ferrar, Anne Ulke-Lemee and Greg BG Moorhead...chr(133David W. Roadcap, Matthew H. Brush, and Shirish Shenolikar...X Assay For 3-Way Interaction Of Protein Phosphatase-1 (Glc7) With Regulatory Subunits Plus Phosphatase Inhibitor-2. Masumi Eto and David L. Brautigan...X Phosphorylation Of The Protein Phosphatase Type 1 Inhibitor Protein, CPI-17, By Protein Kinase C. Michael P. Walsh, Marija Susnjar, Jingti Deng, Cindy Sutherland, Eniko Kiss, and David P. Wilson...X Purification Of Smooth Muscle Myosin Phosphatase Using A Thiophosphorylated Myosin Light Chain-Affinity Resin. Merideth Borman and Justin MacDonald...X Proteins Interacting With Saccharomyces Cerevisiae Type 1 Protein Phosphatase Catalytic Subunit Identified By Single-Step Affinity Purification And Mass Spectrometry.
Book
The new edition of Physicochemical and Environmental Plant Physiology uses elementary chemistry, physics, and mathematics to explain and develop key concepts in plant physiology. In fundamental ways, all physiological processes that occur in cells, tissues, organs, and organisms obey such relations. Topics include diffusion, membranes, water relations, ion transport, photochemistry, bioenergetics of energy conversion, photosynthesis, environmental influences on plant temperature, and gas exchange for leaves and whole plants. This new edition maintains the unparalleled commitment to clear presentation and improves upon the user friendliness of the previous versions. * All illustrations have been redrawn, many in two-color * New material includes: 14 new figures, 100 new references, 20 new equations and considerable new and revised text * Extensive cross-referencing with a simpler system for chapter sections and subsections * Easy-to-use format including major equations being presented at the beginning of each chapter, and calculations presented outside of the chapter text. Physicochemical and Environmental Plant Physiology, 3rd edition, establishes a new standard of excellence in the teaching and quantitative understanding of plant physiology.
Book
The complex roles of glutathione and sulfur amino acids in human health Glutathione (?-L-glutamyl-L-cysteinylglycine, GSH) is a major antioxidant acting as a free radical scavenger that protects the cell from reactive oxygen species (ROS). Sulfur amino acids (SAAs), such as methionine and cysteine, play a critical role in the maintenance of health. GSH depletion as well as alterations of SAA metabolism are linked to a host of disease states including liver cirrhosis, various pulmonary diseases, myocardial ischemia and reperfusion injury, aging, Parkinson's disease, Alzheimer's disease, sepsis, and others. This book provides researchers with a comprehensive review of the biochemistry, absorption, metabolism, biological activities, disease prevention, and health promotion of glutathione and sulfur amino acids. The twenty-two chapters explore such topics as: • Chemistry, absorption, transport, and metabolism of GSH and sulfur amino acids • Antioxidant and detoxification properties of GSH and sulfur amino acids, highlighting the enzymatic systems involved in antioxidant defenses • Biological activities of GSH and sulfur amino acids and their role in modulating cell processes • Role of GSH and sulfur amino acid deficiency and alteration in the onset of diseases and in aging • Protective effects exerted by GSH and sulfur amino acids when used as drugs, functional foods, and nutraceuticals in humans and animals Special attention is paid to the molecular mechanisms for the modulation of transcription factors and enzyme activities, as well as the nutritional and therapeutic significance of dietary sulfur amino acids as shown in human and animal models. With more than 2,000 scientific references, this book provides food scientists, nutritionists, biochemists, food technologists, chemists, molecular biologists, and public health professionals with a comprehensive and up-to-date examination of glutathione and sulfur amino acids in human health and disease.
Book
A comprehensive guide to cutting-edge tools in ADME research. The last decade has seen tremendous progress in the development of analytical techniques such as mass spectrometry and molecular biology tools, resulting in important advances in drug discovery, particularly in the area of absorption, distribution, metabolism, and excretion (ADME). ADME-Enabling Technologies in Drug Design and Development focuses on the current state of the art in the field, presenting a comprehensive review of the latest tools for generating ADME data in drug discovery. It examines the broadest possible range of available technologies, giving readers the information they need to choose the right tool for a given application, a key requisite for obtaining favorable results in a timely fashion for regulatory filings. With over thirty contributed chapters by an international team of experts, the book provides: A thorough examination of current tools, covering both electronic/mechanical technologies and biologically based ones. Coverage of applications for each technology, including key parameters, optimal conditions for intended results, protocols, and case studies. Detailed discussion of emerging tools and techniques, from stem cells and genetically modified animal models to imaging technologies. Numerous figures and diagrams throughout the text. Scientists and researchers in drug metabolism, pharmacology, medicinal chemistry, pharmaceutics, toxicology, and bioanalytical science will find ADME-Enabling Technologies in Drug Design and Development an invaluable guide to the entire drug development process, from discovery to regulatory issues.