Saccharomyces cerevisiae as a model in ecotoxicological studies: A post-genomics perspective

DNA adduct formation in Saccharomyces cerevisiae following exposure to environmental pollutants, as in vivo model for molecular toxicity studies

DNA adduction in the model yeast Saccharomyces cerevisiae was investigated after exposure to the fungicide penconazole and the reference genotoxic compound benzo(a)pyrene, for validating yeasts as a tool for molecular toxicity studies, particularly of environmental pollution. The effect of the toxicants on the yeast's growth kinetics was determined as an indicator of cytotoxicity. Fermentative cultures of S. cerevisiae were exposed to 2 ppm of Penconazole during different phases of growth; while 0.2 and 2 ppm of benzo(a)pyrene were applied to the culture medium before inoculation and on exponential cultures. Exponential respiratory cultures were also exposed to 0.2 ppm of B(a)P for comparison of both metabolisms. Penconazole induced DNA adducts formation in the exponential phase test; DNA adducts showed a peak of 54.93 adducts/109 nucleotides. Benzo(a)pyrene induced the formation of DNA adducts in all the tests carried out; the highest amount of 46.7 adducts/109 nucleotides was obtained in the fermentative cultures after the exponential phase exposure to 0.2 ppm; whereas in the respiratory cultures, 14.6 adducts/109 nucleotides were detected. No cytotoxicity was obtained in any experiment. Our study showed that yeast could be used to analyse DNA adducts as biomarkers of exposure to environmental toxicants.

Dinitroaniline herbicides: a comprehensive review of toxicity and side effects on animal non-target organisms

The widespread use of herbicides has increased concern about the hazards and risks to animals living in terrestrial and aquatic ecosystems. A comprehensive understanding of their effective action at different levels of biological organization is critical for establishing guidelines to protect ecosystems and human health. Dinitroanilines are broad-spectrum pre-emergence herbicides currently used for weed control in the conventional agriculture. They are considered extremely safe agrochemicals because they act specifically on tubulin proteins and inhibit shoot and root growth of plants. However, there is a lack of toxicity information regarding the potential risk of exposure to non-target organisms. The aim of the present review is to focus on side effects of the most commonly used active ingredients, e.g. pendimethalin, oryzalin, trifluralin and benfluralin, on animal non-target cells of invertebrates and vertebrates. Acute toxicity varies from slightly to high in terrestrial and aquatic species (i.e. nematodes, earthworms, snails, insects, crustaceans, fish and mammals) depending on the species-specific ability of tested organisms to adsorb and discharge toxicants. Cytotoxicity, genotoxicity and activation of oxidative stress pathways as well as alterations of physiological, metabolic, morphological, developmental and behavioural traits, reviewed here, indicate that exposure to sublethal concentrations of active ingredients poses a clear hazard to animals and humans. Further research is required to evaluate the molecular mechanisms of action of these herbicides in the animal cell and on biological functions at multiple levels, from organisms to communities, including the effects of commercial formulations.

Towards the Development of Microbial Ecotoxicology Testing Using Chlorpyrifos Contaminated Sediments and Marine Yeast Isolates as a Model

Chlorpyrifos (CP), a widely used pesticide, and its metabolite 3,5,6-trichloro-2-pyridinol (3,5,6-TCP), are xenobiotic compounds detected in many biomes, notably in marine sediments, all over the world. These compounds are posing a serious environmental and health problem given their toxicity to wildlife and possible exposure effects to human neurodevelopment. Microorganisms at CP-impacted environments could harbor metabolic capabilities that can be used as indicators of the biological effects of the contaminant and could encode selected functions reactive against contaminants. Those features could be used for microbial ecotoxicology applications by collectively using analytical, enzymatic, microbiological and toxicological techniques in order to assess the biological effects of pollutants and other environmental/climatic stressors in ecosystems. The objective of this study was to assess the variability in the metabolic responses of yeast isolates from CP-contaminated marine sediments as potential biological indicators for microbial ecotoxicology testing. Sediment samples from a South Caribbean tropical shore (Cartagena Bay, Colombia) were collected, and deoxyribonucleic acid (DNA) was recovered from lyophilized aliquots. The DGGE (Denaturing Gradient Gel Electrophoresis) technique targeting fungal Internal Transcribed Spacer (ITS) showed the great diversity of fungal types. Simultaneously, yeast strains were isolated from the freshly collected sediment samples. Physiological characterization including API 20C and antibiosis tests, growth patterns at salt concentrations (2/4/10/25%), temperatures (4/25/37/45 °C), esterase activity assay and resistance tests to CP/TCP toxicity resulted in 10 isolated yeast strains, identified as Candida spp. (6), Cryptococcus spp. (3). and Rhodotorula spp. (1), showing promising characteristics to be used as a test for yeast-based ecotoxicity indicators. The patterns of carbohydrate assimilation, low antibiosis, presence of esterases/lipases, growth in a wide range of temperatures and salt concentrations, and tolerance to minimal inhibitory concentrations of CP and TCP are factors useful for testing environmental samples.

Gene-Regulated Release of Distinctive Volatile Organic Compounds from Stressed Living Cells

Breath-borne volatile organic compounds (VOCs) have been increasingly studied as non-invasive biomarkers in both medical diagnosis and environmental health research. Recently, changes in breath-borne VOC fingerprints were demonstrated in rats and humans following pollutant exposures. In this study, the eukaryotic model Saccharomyces cerevisiae was used to study the release of cellular VOCs resulting from toxicant exposures (i.e., O₃, H₂O₂, and CO₂) and its underlying biological mechanism. Our results showed that different toxicant exposures caused the release of distinctive VOC profiles of yeast cells. The levels of ethyl acetate and ethyl n-propionate were altered in response to all the toxicants used in this study and could thus be targeted for future environmental toxicity monitoring. The RNA-seq results revealed significant changes in the metabolic or signaling pathways related to the ribosome, carbohydrate, and amino acid metabolisms after exposures. Notably, the shift from glycolysis to the pentose phosphate pathway of carbohydrate metabolism and the inhabitation of the aspartate pathway in the lysine synthesis was essential to the cellular antioxidation by providing reduced nicotinamide adenine dinucleotide phosphate (NADPH). The reprogrammed metabolisms could have resulted in the observed changes of VOCs released, e.g., the production of ethyl acetate for detoxification from yeast cells. This study provides further evidence that VOCs released from living organisms could be used to monitor and guard against toxic exposures while providing better mechanistic insights of the changes in breath-borne VOCs previously observed in rats and humans exposed to air toxicants.

Multi-omics based strategy for toxicity analysis of acrylamide in Saccharomyces cerevisiae model

Although the toxicity of acrylamide (ACR) has been extensively investigated in different experimental models, its perturbations to multiple nodes of the cellular signaling network have not been systematically associated. In this study, changes at different omics layers in ACR exposed Saccharomyces cerevisiae cells were monitored using a multi-omics strategy. The results of the analysis highlighted the impairment of oxidative-reductive balance, energy metabolism, lipid metabolism, nucleotide metabolism, and ribosome function in yeast cells. Response to acute ACR damage, glutathione synthesis was upregulated, the process of protein degradation was accelerated, and the autophagy flux was initiated. Meanwhile, yeast upregulates gene expression levels of enzymes in carbohydrate metabolism and speeds up the oxidation process of fatty acids to compensate for energy depletion. Importantly, the multi-omics strategy captures features that have rarely been addressed in previous studies on the toxicology of ACR, including blocked de novo nucleotide synthesis, decreased levels of metabolic enzyme cofactors thiamine and D-biotin, increased intracellular concentrations of neurotoxic N-methyl d-aspartic acid and l-glutamic acid, and release of death mediators ceramide. The ACR perturbation network constructed in this work and the discovery of new damage features provide a theoretical basis for subsequent point-to-point toxicological studies.

Toxicological assessment of commercial monolayer tungsten disulfide nanomaterials aqueous suspensions using human A549 cells and the model fungus Saccharomyces cerevisiae

The utilization of tungsten disulfide (WS₂) nanomaterials in distinct applications is raising due to their unique physico-chemical properties, such as low friction coefficient and high strength, which highlights the necessity to study their potential toxicological effects, due to the potential increase of environmental and human exposure. The aim of this work was to analyze commercially available aqueous dispersions of monolayer tungsten disulfide (2D WS₂) nanomaterials with distinct lateral size employing a portfolio of physico-chemical and toxicological evaluations. The structure and stoichiometry of monolayer tungsten disulfide (WS₂-ACS-M) and nano size monolayer tungsten disulfide (WS₂-ACS-N) was analyzed by Raman spectroscopy, whereas a more quantitative approach to study the nature of formed oxidized species was undertaken employing X-ray photoelectron spectroscopy. Adenocarcinomic human alveolar basal epithelial cells (A549 cells) and the ecotoxicology model Saccharomyces cerevisiae were selected as unicellular eukaryotic systems to assess the cytotoxicity of the nanomaterials. Cell viability and reactive oxygen species (ROS) determinations demonstrated different toxicity levels depending on the cellular model used. While both 2D WS₂ suspensions showed very low toxicity towards the A549 cells, a comparable concentration (160 mg L^-1) reduced the viability of yeast cells. The toxicity of a nano size 2D WS₂ commercialized in dry form from the same provider was also assessed, showing ability to reduce yeast cells viability as well. Overall, the presented data reveal the physico-chemical properties and the potential toxicity of commercial 2D WS2 aqueous suspensions when interacting with distinct eukaryotic organisms, showing differences in function of the biological system exposed.

Microbial bioassays in environmental toxicity testing

Accidental spills and the misuse of chemicals may lead to current and legacy environmental contamination and pose concerns over possible (eco)toxicological secondary effects and risks toward non-target microbes and higher eukaryotes, including humans, in ecosystems. In the last decades, scientists and regulators have faced requests to thoroughly screen, prioritize and predict the possible deleterious effects of the huge numbers of existing and emerging xenobiotics, wastewaters and environmental samples on biological systems. In this context, it has become necessary to develop and validate (eco)toxicity bioassays based on microorganisms (e.g., bacteria, microalga, yeast, filamentous fungi, protozoa) as test-organisms whose data should be meaningful for environmental (micro)organisms that may be exposed to contaminated environments. These generally simple, fast and cost-effective bioassays may be preliminary and complementary to the more complex and long-term whole-organism animal-based traditional ecotoxicity tests. With the goal of highlighting the potential offered by microbial-based bioassays as non-animal alternatives in (eco)toxicity testing, the present chapter provides an overview of the current state-of-the art in the development and use of microbial toxicity bioassays through the examination of relatively recent examples with a diverse range of toxicity endpoints. It goes into the (eco)toxicological relevance of these bioassays, ranging from the more traditional microalga- and bacterial-based assays already accepted at regulatory level and commercially available to the more innovative microbial transcriptional profiling and gene expression bioassays, including some examples of biosensors.

Harmful effects of metal(loid) oxide nanoparticles

The incorporation of nanomaterials (NMs), including metal(loid) oxide (MOx) nanoparticles (NPs), in the most diversified consumer products, has grown enormously in recent decades. Consequently, the contact between humans and these materials increased, as well as their presence in the environment. This fact has raised concerns and uncertainties about the possible risks of NMs to human health and the adverse effects on the environment. These concerns underline the need and importance of assessing its nanosecurity. The present review focuses on the main mechanisms underlying the MOx NPs toxicity, illustrated with different biological models: release of toxic ions, cellular uptake of NPs, oxidative stress, shading effect on photosynthetic microorganisms, physical restrain and damage of cell wall. Additionally, the biological models used to evaluate the potential hazardous of nanomaterials are briefly presented, with particular emphasis on the yeast Saccharomyces cerevisiae, as an alternative model in nanotoxicology. An overview containing recent scientific advances on cellular responses (toxic symptoms exhibited by yeasts) resulting from the interaction with MOx NPs (inhibition of cell proliferation, cell wall damage, alteration of function and morphology of organelles, presence of oxidative stress bio-indicators, gene expression changes, genotoxicity and cell dead) is critically presented. The elucidation of the toxic modes of action of MOx NPs in yeast cells can be very useful in providing additional clues about the impact of NPs on the physiology and metabolism of the eukaryotic cell. Current and future trends of MOx NPs toxicity, regarding their possible impacts on the environment and human health, are discussed. KEY POINTS: • The potential hazardous effects of MOx NPs are critically reviewed. • An overview of the main mechanisms associated with MOx NPs toxicity is presented. • Scientific advances about yeast cell responses to MOx NPs are updated and discussed.

Assessment of Physico-Chemical and Toxicological Properties of Commercial 2D Boron Nitride Nanopowder and Nanoplatelets

Boron nitride (BN) nanomaterials have been increasingly explored for potential applications in chemistry and biology fields (e.g., biomedical, pharmaceutical, and energy industries) due to their unique physico-chemical properties. However, their safe utilization requires a profound knowledge on their potential toxicological and environmental impact. To date, BN nanoparticles have been considered to have a high biocompatibility degree, but in some cases, contradictory results on their potential toxicity have been reported. Therefore, in the present study, we assessed two commercial 2D BN samples, namely BN-nanopowder (BN-PW) and BN-nanoplatelet (BN-PL), with the objective to identify whether distinct physico-chemical features may have an influence on the biological responses of exposed cellular models. Morphological, structural, and composition analyses showed that the most remarkable difference between both commercial samples was the diameter of their disk-like shape, which was of 200-300 nm for BN-PL and 100-150 nm for BN-PW. Their potential toxicity was investigated using adenocarcinomic human alveolar basal epithelial cells (A549 cells) and the unicellular fungus Saccharomycescerevisiae, as human and environmental eukaryotic models respectively, employing in vitro assays. In both cases, cellular viability assays and reactive oxygen species (ROS) determinations where performed. The impact of the selected nanomaterials in the viability of both unicellular models was very low, with only a slight reduction of S. cerevisiae colony forming units being observed after a long exposure period (24 h) to high concentrations (800 mg/L) of both nanomaterials. Similarly, BN-PW and BN-PL showed a low capacity to induce the formation of reactive oxygen species in the studied conditions. Even at the highest concentration and exposure times, no major cytotoxicity indicators were observed in human cells and yeast. The results obtained in the present study provide novel insights into the safety of 2D BN nanomaterials, indicating no significant differences in the toxicological potential of similar commercial products with a distinct lateral size, which showed to be safe products in the concentrations and exposure conditions tested.

Cytotoxic and estrogenic activity of chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol. Study of marine yeasts as potential toxicity indicators

Chlorpyrifos (CP) is one of the organophosphate insecticides most used worldwide today. Although the main target organ for CP is the nervous system triggering predominantly neurotoxic effects, it has suggested other mechanisms of action as cytotoxicity and endocrine disruption. The risk posed by the pesticide metabolites on non-target organisms is increasingly recognized by regulatory agencies and natural resource managers. In the present study, cytotoxicity and estrogenic activity of CP, and its principal metabolite 3,5,6-trichloro-2-pyridinol (TCP) have been evaluated by in vitro assays, using two mammalian cell lines (HEK293 and N2a), and a recombinant yeast. Results indicate that TCP is more toxic than CP for the two cell lines assayed, being N2a cells more sensitive to both compounds. Both compounds show a similar estrogenic activity being between 2500 and 3000 times less estrogenic than 17β-estradiol. In order to find new toxicity measurement models, yeasts isolated from marine sediments containing CP residues have been tested against CP and TCP by cell viability assay. Of the 12 yeast strains tested, 6 of them showed certain sensitivity, and a concentration-dependent response to the tested compounds, so they could be considered as future models for toxicity tests, although further investigations and proves are necessary.

Interaction between Polyphenolic Antioxidants and Saccharomyces cerevisiae Cells Defective in Heavy Metal Transport across the Plasma Membrane

Natural polyphenols are compounds with important biological implications which include antioxidant and metal-chelating characteristics relevant for their antimicrobial, antitumor, or antiaging potential. The mechanisms linking polyphenols and heavy metals in their concerted actions on cells are not completely elucidated. In this study, we used the model eukaryotic microorganism Saccharomyces cerevisiae to detect the action of widely prevalent natural polyphenols on yeast cells defective in the main components involved in essential heavy metal transport across the plasma membrane. We found that caffeic and gallic acids interfered with Zn accumulation, causing delays in cell growth that were alleviated by Zn supplementation. The flavones morin and quercetin interfered with both Mn and Zn accumulation, which resulted in growth improvement, but supplemental Mn and especially Zn turned the initially benefic action of morin and quercetin into potential toxicity. Our results imply that caution is needed when administering food supplements or nutraceuticals which contain both natural polyphenols and essential elements, especially zinc.

Fate assessment of commercial 2D MoS2 aqueous dispersions at physicochemical and toxicological level

The physicochemical properties and the toxicological potential of commercially available MoS₂ nanoparticles with different lateral size and degradation stage were studied in the present research work. To achieve this, the structure and stoichiometry of fresh and old aqueous suspensions of micro-MoS₂ and nano-MoS₂ was analyzed by Raman, while x-ray photoelectron spectroscopy allowed to identify more quantitatively the nature of the formed oxidized species. A, the toxicological impact of the nanomaterials under analysis was studied using adenocarcinomic human alveolar basal epithelial cells (A549 cells) and the unicellular fungus S. cerevisiae as biological models. Cell viability assays and reactive oxygen species (ROS) determinations demonstrated different toxicity levels depending on the cellular model used and in function of the degradation state of the selected commercial nanoproducts. Both MoS₂ nanoparticle types induced sublethal damage on the A549 cells though the increase of intracellular ROS levels, while comparable concentrations reduced the viability of yeast cells. In addition, the old MoS₂ nanoparticles suspensions exhibited a higher toxicity for both human and yeast cells than the fresh ones. Our findings demonstrate that the fate assessment of nanomaterials is a critical aspect to increase the understanding on their characteristics and on their potential impact on biological systems along their life cycle.

Control of pesticides in Ecuador: An underrated problem?

Pesticides have become necessary control agents to guarantee food sovereignty and strengthen development in Ecuador. Nevertheless, the current management practices of pesticides in Ecuador restrain the progress of agriculture in this region. There is evidence of a knowledge gap regarding the correct handling of pesticides and the possible health impacts they generate, especially in small producers and surrounding communities. Furthermore, a lack of updated information on pesticide registration difficult their control and distribution. Given this, there is a need to implement new public policies that promote relations between science and technology, not only with the industry but also with local producers, to promote the growth of agriculture, minimizing risks to health and the environment in the sectors involved. The purpose of this review is to exhibit the most updated panorama regarding the management of pesticides in Ecuador.

Preventive Effects of Three Polysaccharides on the Oxidative Stress Induced by Acrylamide in a Saccharomyces cerevisiae Model

Saccharomyces cerevisiae was used as a model to explore the preventive effect of two marine polysaccharides separately derived from Sepia esculenta ink (SIP) and Laminaria japonica (FL) as well as one terrestrial polysaccharides from Eleocharis tuberosa peel (WCPP) on toxic injury induced by acrylamide (AA). The growth of yeast was evaluated by kinetics indexes including doubling time, lag phase and maximum proliferation density. Meanwhile, intracellular redox state was determined by contents of MDA and GSH, and SOD activity. The results showed that AA inhibited yeast growth and destroyed the antioxidant defense system. Supplement with polysaccharides, the oxidative damage of cells was alleviated. According to the growth recovery of yeast, FL and WCPP had similar degree of capacity against AA associated cytotoxicity, while SIP was 1.5~2 folds as strong as FL and WCPP. SIP and FL significantly reduced production of MDA by AA administration. Moreover, SIP, FL and WCPP increased SOD activity and repressed GSH depletion caused by AA.

Combining proteomics and lipid analysis to unravel Confidor stress response in Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae is a useful model for studying the influence of different stress factors on eukaryotic cells. In this work we used the pesticide imidacloprid, in the Confidor formulation, as the stress factor and analyzed its influence on the metabolic activity, proteome and lipid content and composition of Saccharomyces cerevisiae yeast. During the cultivation of yeast, the lowest recommended application dose of Confidor (0.025%, v/v) was added to the growth media and its influence on the mitochondria, cytosol with microsomes, and the whole yeast cells was monitored. The results show that under the stress provoked by the toxic effects of Confidor, yeast cells density significantly decreased and the percentage of metabolically disturbed cells significantly increased comparing with untreated control. Also, there was a downregulation of majority of glycolytic, gluconeogenesis, and TCA cycle enzymes (Fba1, Adh1, Hxk2, Tal1, Tdh1,Tdh3, Eno1) thus providing enough acetyl-CoA for the lipid restructuring and accumulation mechanism since we have found the changes in the cell and mitochondrial lipid content and FA composition. This data suggest that lipids could be the molecules that orchestrate the answer of the cells in the stress response to the Confidor treatment.

Effects of MCHM on yeast metabolism

On January 2014 approximately 10,000 gallons of crude 4-Methylcyclohexanemethanol (MCHM) and propylene glycol phenol ether (PPH) were accidentally released into the Elk River, West Virginia, contaminating the tap water of around 300,000 residents. Crude MCHM is an industrial chemical used as flotation reagent to clean coal. At the time of the spill, MCHM's toxicological data were limited, an issue that has been addressed by different studies focused on understanding the immediate and long-term effects of MCHM on human health and the environment. Using S. cerevisiae as a model organism we study the effect of acute exposure to crude MCHM on metabolism. Yeasts were treated with MCHM 550 ppm in YPD for 30 minutes. Polar and lipid metabolites were extracted from cells by a chloroform-methanol-water mixture. The extracts were then analyzed by direct injection ESI-MS and by GC-MS. The metabolomics analysis was complemented with flux balance analysis simulations done with genome-scale metabolic network models (GSMNM) of MCHM treated vs non-treated control. We integrated the effect of MCHM on yeast gene expression from RNA-Seq data within these GSMNM. A total of 215 and 73 metabolites were identified by the ESI-MS and GC-MS procedures, respectively. From these 26 and 23 relevant metabolites were selected from ESI-MS and GC-MS respectively, for 49 unique compounds. MCHM induced amino acid accumulation, via its effects on amino acid metabolism, as well as a potential impairment of ribosome biogenesis. MCHM affects phospholipid biosynthesis, with a potential impact on the biophysical properties of yeast cellular membranes. The FBA simulations were able to reproduce the deleterious effect of MCHM on cellular growth and suggest that the effect of MCHM on ubiquinol:ferricytochrome c reductase reaction, caused by the under-expression of CYT1 gene, could be the driven force behind the observed effect on yeast metabolism and growth.

Multiple-Omics Techniques Reveal the Role of Glycerophospholipid Metabolic Pathway in the Response of Saccharomyces cerevisiae Against Hypoxic Stress

Although the biological processes of organism under hypoxic stress had been elucidated, the whole physiological changes of Saccharomyces cerevisiae are still unclear. In this work, we investigated the changes of biological process of S. cerevisiae under hypoxia by the methods of transcriptomics, proteomics, metabolomics, and bioinformatics. The results showed that the expression of a total of 1017 mRNA in transcriptome, 213 proteins in proteome, and 51 metabolites in metabolome had been significantly changed between the hypoxia and normoxia conditions. Moreover, based on the integration of system-omics data, we found that the carbohydrate, amino acids, fatty acid biosynthesis, lipid metabolic pathway, and oxidative phosphorylation were significantly changed in hypoxic stress. Among these pathways, the glycerophospholipid metabolic pathway was remarkably up-regulated from the mRNA, protein, and metabolites levels under hypoxic stress, and the expression of relevant mRNA was also confirmed by the qPCR. The metabolites of glycerophospholipid pathway such as phosphatidylcholine, phosphatidylethanolamine, phosphoinositide, and phosphatidic acids probably maintained the stability of cell membranes against hypoxic stress to relieve the cell injury, and kept S. cerevisiae survive with energy production. These findings in the hypoxic omics and integrated networks provide very useful information for further exploring the molecular mechanism of hypoxic stress.

Zinc oxide nanoparticles impose metabolic toxicity by de-regulating proteome and metabolome in Saccharomyces cerevisiae

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Untargeted proteomic and metabolic approaches provide complete toxicity assessment.

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ZnO-NPs de-regulate the proteome and metabolome of S. cerevisiae.

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ZnO-NPs affect the key metabolites of central metabolic pathways.

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Protein and/or metabolite can be used as biomarker specific to the ZnO-NPs induced toxicity.

As zinc oxide nanoparticles are being increasingly used in various applications, it is important to assess their potential toxic implications. Stress responses and adaptations are primarily controlled by modulation in cellular proteins (enzyme) and concentration of metabolites. To date proteomics or metabolomics applications in nanotoxicity assessment have been applied to a restricted extent. Here we utilized 2DE and ¹H NMR based proteomics and metabolomics respectively to delineate the toxicity mechanism of zinc oxide nanoparticles (ZnO-NPs) in budding yeast S. cerevisiae. We found that the physiological and metabolic processes were altered in the S. cerevisiae upon ZnO-NPs exposure. Almost 40% proteins were down-regulated in ZnO-NPs (10 mg L⁻¹) exposed cell as compared to control. Metabolomics and system biology based pathway analysis, revealed that ZnO-NPs repressed a wide range of key metabolites involved in central carbon metabolism, cofactors synthesis, amino acid and fatty acid biosynthesis, purines and pyrimidines, nucleoside and nucleotide biosynthetic pathways. These metabolic changes may be associated with the energy metabolism, antioxidation, DNA and protein damage and membrane stability. We concluded that untargeted proteomic and metabolic approaches provide more complete measurements and suggest probable molecular mechanisms of nanomaterials toxicity.

Effects of selenium on oxidative damage and antioxidant enzymes of eukaryotic cells: wine Saccharomyces cerevisiae

AIM

To clarify the effects of selenium (Se), parameters related to oxidative issues, as well as the antioxidant response were investigated on an autochthonous wine yeast strain.

METHODS AND RESULTS

Antioxidant enzyme activity, gel electrophoresis, Western blot and MDA level were used to investigate the effects of different concentration of Se in wine yeast. We found that Se is able to affect the enzymatic activities of catalase (CAT), glutathione peroxidase (GPx) and superoxide dismutase (SOD). An increase in lipid peroxidation was observed in a dose-dependent manner of (Se), thus, indicating the occurrence of cell membrane damage. Additionally, Se induced post-translational oxidative modifications of proteins, especially oxidation of thiol groups (both reversible and irreversible) and protein carbonylation (irreversible oxidation).

CONCLUSION

These results obtained could further the understanding the effect of different concentration of Se in wine yeast strain with which Se affect the enzymatic activities and induces some post-translational modifications of proteins.

SIGNIFICANCE AND IMPACT OF THE STUDY

The understanding of mechanisms regulating the response of wine yeast to Se is important for future work using selenized yeast as enriched Se supplements in human nutrition.

Towards Simazine Monitoring in Agro-Zootechnical Productions: A Yeast Cell Bioprobe for Real Samples Screening

Simazine is an herbicide that is able to contaminate surface waters, ground waters, and milk/dairy products, thus posing concerns in both environmental health and food safety. A yeast-based bioprobe was utilized to detect simazine in spiked real samples of livestock drinking water and raw cow's milk. Yeast aerobic respiration was taken as short-term toxicological endpoint. We carried out comparative measures of yeast oxygen consumption between simazine-spiked samples and blank samples. Percentage interference (%ρ) on yeast aerobic respiration was calculated through the comparison of aerobic respiration of simazine-exposed and non-exposed yeast cells. The method was optimized for raw cow's milk samples by using boric acid as fungistatic agent in order to avoid cellular proliferation. Overall, the results have shown that simazine can be detected up to concentrations five times below the EU legal concentration limits for drinking water (0.02 ppb) and cow's milk (2 ppb) (%ρ values of 18.53% and 20.43% respectively; %RSD ≤ 15%). Dose-effect relationships of simazine were assessed. The findings of the bioassays match reasonably well with known mechanisms of toxicity and intracellular detoxification in yeast. A correlation between fat content in milk samples and analytical performance of the bioprobe was established. Results suggest the involvement of a matrix effect, presumably due to lipid sequestration of simazine. The yeast-based bioprobe has proved to be sensitive and suitable for the detection of simazine in real samples in concentrations of interest.

Comparative analysis of transcriptomic responses to sub-lethal levels of six environmentally relevant pesticides in Saccharomyces cerevisiae

Accidental spills and misuse of pesticides may lead to current and/or legacy environmental contamination and may pose concerns regarding possible risks towards non-target microbes and higher eukaryotes in ecosystems. The present study was aimed at comparing transcriptomic responses to effects of sub-lethal levels of six environmentally relevant pesticide active substances in the Saccharomyces cerevisiae eukaryotic model. The insecticide carbofuran, the fungicide pyrimethanil and the herbicides alachlor, S-metolachlor, diuron and methyl(4-chloro-2-methylphenoxy)acetate were studied. Some are currently used agricultural pesticides, while others are under restricted utilization or banned in Europe and/or North America albeit being used in other geographical locations. In the present work transcriptional profiles representing genome-wide responses in a standardized yeast population upon 2 h of exposure to concentrations of each compound exerting equivalent toxic effects, i.e., inhibition of growth by 20% relative to the untreated control cells, were examined. Hierarchical clustering and Venn analyses of the datasets of differentially expressed genes pointed out transcriptional patterns distinguishable between the six active substances. Functional enrichment analyses allowed predicting mechanisms of pesticide toxicity and response to pesticide stress in the yeast model. In general, variations in transcript numbers of selected genes assessed by Real-Time quantitative reverse transcription polymerase chain reaction confirmed microarray data and correlated well with growth inhibitory effects. A possible biological relevance of mechanistic predictions arising from these comparative transcriptomic analyses is discussed in the context of better understanding potential modes of action and adverse side-effects of pesticides.

Toxicity Effects of Functionalized Quantum Dots, Gold and Polystyrene Nanoparticles on Target Aquatic Biological Models: A Review

Nano-based products are widespread in several sectors, including textiles, medical-products, cosmetics, paints and plastics. Nanosafety and safe-by-design are driving nanoparticle (NP) production and applications through NP functionalization (@NPs). Indeed, @NPs frequently present biological effects that differ from the parent material. This paper reviews the impact of quantum dots (QDs), gold nanoparticles (AuNPs), and polystyrene-cored NPs (PSNPs), evidencing the role of NP functionalization in toxicity definition. Key biological models were taken into consideration for NP evaluation: Saccharomyces cerevisiae, fresh- (F) and saltwater (S) microalgae (Raphidocelis subcapitata (F), Scenedesmus obliquus (F) and Chlorella spp. (F), and Phaeodactylum tricornutum (S)), Daphnia magna, and Xenopus laevis. QDs are quite widespread in technological devices, and they are known to induce genotoxicity and oxidative stress that can drastically change according to the coating employed. For example, AuNPs are frequently functionalized with antimicrobial peptides, which is shown to both increase their activity and decrease the relative environmental toxicity. P-NPs are frequently coated with NH₂⁻ for cationic and COOH⁻ for anionic surfaces, but when positively charged toxicity effects can be observed. Careful assessment of functionalized and non-functionalized NPs is compulsory to also understand their potential direct and indirect effects when the coating is removed or degraded.

Application of proteomics to the study of Helicobacter pylori and implications for the clinic

INTRODUCTION

Helicobacter pylori (H. pylori) is a gram-negative bacterium that colonizes the gastric epithelium and mucous layer of more than half the world's population. H. pylori is a primary human pathogen, responsible for the development of chronic gastritis, peptic ulceration and gastric cancer. Proteomics is impacting several aspects of medical research: understanding the molecular basis of infection and disease manifestation, identification of therapeutic targets and discovery of clinically relevant biomarkers. Areas covered: The main aim of the present review is to provide a comprehensive overview of the contribution of proteomics to the study of H. pylori infection pathophysiology. In particular, we focused on the role of the bacterium and its most important virulence factor, CagA, in the progression of gastric cells transformation and cancer progression. We also discussed the proteomic approaches aimed at the investigation of the host response to bacterial infection. Expert commentary: In the field of proteomics of H. pylori, comprehensive analysis of clinically relevant proteins (functional proteomics) rather than entire proteomes will result in important medical outcomes. Finally, we provided an outlook on the potential development of proteomics in H. pylori research.

Omics analysis of acetic acid tolerance in Saccharomyces cerevisiae

Acetic acid is an inhibitor in industrial processes such as wine making and bioethanol production from cellulosic hydrolysate. It causes energy depletion, inhibition of metabolic enzyme activity, growth arrest and ethanol productivity losses in Saccharomyces cerevisiae. Therefore, understanding the mechanisms of the yeast responses to acetic acid stress is essential for improving acetic acid tolerance and ethanol production. Although 329 genes associated with acetic acid tolerance have been identified in the Saccharomyces genome and included in the database ( http://www.yeastgenome.org/observable/resistance_to_acetic_acid/overview ), the cellular mechanistic responses to acetic acid remain unclear in this organism. Post-genomic approaches such as transcriptomics, proteomics, metabolomics and chemogenomics are being applied to yeast and are providing insight into the mechanisms and interactions of genes, proteins and other components that together determine complex quantitative phenotypic traits such as acetic acid tolerance. This review focuses on these omics approaches in the response to acetic acid in S. cerevisiae. Additionally, several novel strains with improved acetic acid tolerance have been engineered by modifying key genes, and the application of these strains and recently acquired knowledge to industrial processes is also discussed.

Identification of the fitness determinants of budding yeast on a natural substrate

The budding yeasts are prime models in genomics and cell biology, but the ecological factors that determine their success in non-human-associated habitats is poorly understood. In North America Saccharomyces yeasts are present on the bark of deciduous trees, where they feed on bark and sap exudates. In the North East, Saccharomyces paradoxus is found on maples, which makes maple sap a natural substrate for this species. We measured growth rates of S. paradoxus natural isolates on maple sap and found variation along a geographical gradient not explained by the inherent variation observed under optimal laboratory conditions. We used a functional genomic screen to reveal the ecologically relevant genes and conditions required for optimal growth in this substrate. We found that the allantoin degradation pathway is required for optimal growth in maple sap, in particular genes necessary for allantoate utilization, which we demonstrate is the major nitrogen source available to yeast in this environment. Growth with allantoin or allantoate as the sole nitrogen source recapitulated the variation in growth rates in maple sap among strains. We also show that two lineages of S. paradoxus display different life-history traits on allantoin and allantoate media, highlighting the ecological relevance of this pathway.