Vacancies

PhD

• PhD Biochemical Ecotoxicology
  

Master thesis topics

• Sex and age dependent mortality of Gammarus pulex in pesticide exposure
  Contact: Anna Maija Nyman
  
  Methods for assessing the toxicity of pesticides to aquatic invertebrates currently do not account for important organism characteristics. For example, the sensitivity to pesticides might be influenced by age and sex. Regarding the population level effects of pesticides, it matters whether the individuals who die are young or old - the young ones have more potential to contribute to the population abundance than old individuals. Equally, if males are more sensitive than females (or vice versa) the chemical disturbs the optimal sex ratio and thus reduces reproductive success of a population. Altogether, sex and age dependent mortality might influence the population abundance to a greater degree than current toxicity test methods would predict.
  
  The Master thesis topic is about investigating whether mortality of Gammarus pulex under exposure to pesticides is influenced by sex and age. Approximately 15 pesticides (e.g. diazinon, propiconazole, imidacloprid, aldicarb, malathion, carbofuran) will be studied and the selection covers various modes of toxic action. Standard acute toxicity test designs will be modified to determine the G. pulex age, size and sex distributions before and after the test. The student will learn how to conduct laboratory experiments with G. pulex, carry out experiments with radiolabelled xenobiotics and statistical analysis of toxicity data.
  Day to day supervision will be provided by Anna-Maija Nyman and Dr. Roman Ashauer.
  
  
  

• Interactions between silver and copper in the alga Chlamydomonas reinhardtii
  Contact: Dr. Renata Behra
  
  Silver nanoparticles are currently one of the most widely commercially used nanomaterials making it likely that silver particles and dissolved silver may be released into the environment. Silver is among the most toxic elements to aquatic organisms. Previous work from our laboratory shows that effects of dissolved Ag+ ions to photosynthesis and chlorophyll a fluorescence in the green algae Chlamydomonas reinhardtii are comparable to those elicited by copper ions. This Master study aims at examining effects of silver and copper ions on growth and photosynthesis in C. reinhardtii and to analyze their mode of joint action.
  
  
  

• Physiological analysis of Chlamydomonas reinhardtii exposed to silver
  Contact: Dr. Smitha Pillai
  
  Silver, a metal widely used for several human applications, is significantly toxic in its ionic form to a variety of aquatic organisms. Understanding biological responses to Ag(+) is important for pollution assessment and monitoring exposure to the environment. A major challenge is to understand the toxic mechanisms at a molecular level and to relate them to functional changes at the physiological, organism and population levels.
  
  A genome wide transcriptome analysis of Chlamydomonas reinhardtii, a model alga, exposed to silver has shown transcripts of proteins of several important biochemical pathways and cellular functions being differentially regulated. The proposed project will investigate how the changes in the trancriptome affects the physiological outcome of the organism and thereby the algal population. For this we propose a targeted approach depending on the transcriptome analyses and to use specific assays of key enzymes in important biochemical pathways.
  If you have the enthusiasm to work in an international research team consisting environmental toxicologists, biochemists and molecular biologists, EAWAG is the place with excellent research facilities.
  
  
  

• Silver in natural waters - method development and field measurements
  Contact: Prof. Laura Sigg
  
  Because of increased use of silver nanoparticles in numerous products, concern about silver inputs into natural waters is raising. Natural background concentrations of silver are expected to be very low (in the range of nanograms per liter), but concentrations both in polluted and unpolluted environments are poorly known. In this master thesis, a method based on diffusion gradients through thin-films (DGT) will be developed for in situ preconcentration of silver and subsequent measurement by ICP-MS. Field measurements will be carried out using this method in natural river water at various sites.

  
  
  

• Development of a multiplex-PCR method to assess chemical toxicity towards fish cells
  Contact: Dr. Katrin Tanneberger and Prof. Kristin Schirmer
  
  In environmental risk assessment fish is the most widely used vertebrate species. Within an international research project we aim to develop a fish cell-based test system to replace or reduce the use of fish needed for Acute Fish toxicity tests (OECD test guideline 203). One possibility to determine the toxic potential of chemicals is the measurement of cytotoxicity using different fluorescent dyes. Another way to assess chemical toxicity is to quantify the expression or repression of stress-responsive genes. By establishing a multiplex-PCR method it is possible to determine the expression/repression of up to 15 genes simultaneously. This will further allow us to identify expression patterns depending on the chemicals toxic mode of action. The proposed master project combines cell culture (working under sterile conditions with fish cell lines) and molecular biology techniques (RNA isolation, PCR, primer design, gel electrophoresis, working with chip technique).
  
  
  

• Effect of changing environmental conditions on the adaptation of photosynthetic organisms to pollutants (multiple stressor effects)
  Contact: Dr. Beat Fischer
  
  In the environment anthropogenic pollutants can change the composition of the ecosystem due to different tolerance of individual organisms to the pollution. Especially in microorganisms chronic exposure often causes genetic adaptation and increased resistance to toxic substances. Beside pollution, climate changes cause additional stress in the environment which can alter the sensitivity and the response of the organisms to hazardous chemicals. To study such multiple stressor effects in photosynthetic organisms, the impact of increased UV-radiation on the toxicity of heavy metals will be analyzed in microalgae. First, we will focus on changes in growth, physiology and molecular response of the algae to short-term treatment with individual and combined stresses. This knowledge will help us to better study and understand the process of adaptation in algal populations during chronic exposure to multiple stressors.
  
  
  

• Development of a fish intestinal barrier model using a novel rainbow trout cell line
  Contact: Prof. Kristin Schirmer
  
  The fish intestine is an important site of nutrient absorption, ion regulation and pathogen defense. At the same time, it may serve as an entry port for contaminants by means of transfer from the fish diet. Little is known thus far about the intestinal cells’ function, in part because of a lack of an appropriate in vitro cell culture model. We therefore have established a cell line from rainbow trout intestine, to our knowledge the first of its kind. The goal of this project is to develop culture and exposure conditions that closely mimic the physiological conditions in fish and to explore how these specifically adapted cells take up and respond to a model toxicant. Thus, work is a combination of cell biology (sterile cell culture techniques; biochemical and cell physiological characterisations) and toxicology (exposure, cellular uptake and response to model contaminant).
  
  
  

• Time- and concentration-dependent uptake and distribution of benzo(a)pyrene in a liver cell line
  Contact: Prof. Kristin Schirmer / Danielle Madureira
  
  In an integrated project of experimental and theoretical biologists, we are investigating time- and concentration dependent responses elicited by benzo(a)pyrene, a polycyclic aromatic hydrocarbon and common environmental contaminant, in a well characterized liver cell line from mouse. Cellular responses, genome and proteome-wide expression are analyzed and linked by different computational tools. In order to link the presence of the chemical to the biological responses observed, it is important to understand the uptake kinetics of benzo(a)pyrene and its cellular distribution. This project therefore aims to quantify the uptake and distribution of the chemical into cells and organelles using radiolabelled benzo(a)pyrene in combination with scintillation counting and potentially radio-HPLC.
  
  
  

• Measurement and simulation of feeding rate inhibition in response to pollutants with the freshwater invertebrate Gammarus pulex
  Contact: Dr. Roman Ashauer
  
  Feeding rate of Gammarus pulex is a direct measure of ecosystem functioning because these organisms are the most important shredders (leaf litter processing) in European streams. Within two projects we are measuring and simulating the time-dependent uptake, biotransformation, elimination and toxic effects of organic xenobiotic pollutants on the freshwater invertebrate Gammarus pulex. The time-course of survival of Gammarus pulex can already be simulated for risk assessment of realistic exposure situations, i.e. fluctuating concentrations and now we would like to include feeding rate as another endpoint. Hence this MSc project has two objectives: (i) measure the inhibition and recovery of Gammarus pulex feeding activity in response to pulses of pollutants such as pesticides and (ii) adapt our existing simulation model to predict feeding rate of Gammarus pulex. The student will be trained in laboratory work with Gammarus pulex and toxicants as well as in computer based modeling of toxic effects for chemical risk assessment.
  
  
  

• Sequential exposure to multiple toxicants - testing the sequence effect
  Contact: Dr. Roman Ashauer
  
  Recently we found that in situations where freshwater organisms are exposed to several pollutants after each other (as happens in real streams and rivers) the sequence of that exposure may have a significant influence on the overall effect. This was shown for compounds which act on the same target site in the freshwater invertebrate Gammarus pulex but exhibit different recovery dynamics. The aims of this MSc thesis are to experimentally investigate the sequence effect of several environmental pollutants on Gammarus pulex. This study will for the first time investigate sequential interaction of toxicants which act on different target sites. The student will be trained in laboratory work with Gammarus pulex and toxicants. The student also has the opportunity to use computer based modeling of toxic effects to design the experiments and gain a better mechanistic understanding of the results.
  
  
  

• Glucocorticoid-like activity screening of municipal and hospital wastewater
  Contact: Dr. Marc Suter
  
  The natural agonists of the glucocorticoid receptor (GR) are cortisol and other glucocorticoids. They regulate immune and stress response, and exert other wide ranging effects on animal physio­logy. Hence GR signaling pathways could be a prime target for endocrine disruptors. A recent Dutch study found significant gluco­corticoid-like activity in raw industrial and hospital effluents, as well as in municipal waste water treatment plant (WWTP) effluents. The levels ranged up to 16 ng cortisol equivalents/L for surface waters, and up to 2'900 ng/L in effluents. The exact causes for this very high activity are unknown, but it may likely be due to synthetic glucocorticoids used as immuno­suppressives and anti-inflammatories.
  
  In view of the physiological importance of glucocorticoid signaling and the negative effects of chronic exposure, the glucocorticoid-like activity in Swiss WWTP effluents will be assessed using a bioanalytical tool, a reporter cell line stably transfected with the human glucocorticoid receptor.