Postdoc in Environmental Chemistry / Gut Microbiolgy in Bern

About Us And The Project We are looking for a motivated early-postdoc (< 3 years post PhD) with analytical and environmental chemistry experience interested in being part of our interdisciplinary project titled “Microbial Degradation of Arsenobetaine in the Human Gut: Implications for Dietary Arsenic Exposure and Risk Assessment.” The project is led by an interfaculty team composed of Prof. Dr. Adrien Mestrot (GIUB, Soil Biogeochemistry, Inorganic Environmental Chemistry), Prof. Dr. Siegfried Hapfelmeier (IFIK, Gut microbiology) and Prof. Dr. Stephanie Ganal-Vonarbrug (DBMR, Immunology, Microbiology). The project will take full advantage of the state-of-the-art facilities present at our institutes (e.g. cLab of the GIUB with HPLC-ICP-MS instruments, anaerobic incubators at IFIK and DBMR) and will rely on ongoing human cohort studies to secure samples. It is funded by and run in close collaboration with the Federal Office for Food Safety and Veterinary Affairs.

Background and objectives

Dietary intake of arsenobetaine (AsB), the dominant arsenic (As) species in fish & seafood, is usually considered harmless due to negligible metabolism and rapid excretion. However, the team leading this project showed in a recent gnotobiotic mouse study that AsB can undergo microbiota-dependent transformations, producing toxic As species. Unfortunately, the extent to which these observations are translatable to humans remains as of today unresolved. Clarifying this question is toxicologically important, as even small AsB conversion to more toxic As species would be relevant for risk assessment.

In this project we aim to determine human gut microbiota mediated AsB transformations using a range of liquid chromatography speciation methods to quantify conversion rates of AsB into toxic As species under relevant exposure conditions and to assess interindividual variability. The hired postdoc will use in vitro human fecal microbiota assays from various donors to establish translational relevance. The results will directly support FSVO/EFSA in evaluating whether AsB-rich seafood may constitute a yet unrecognized source of toxic As species in humans.

Your tasks and our expectations

• Establish robust analytical methods to determine AsB transformation in fecal microbiota: extraction from samples as well as method validation for a range of arsenic speciation methods using HPLC-ICP-MS/MS
• Establish robust experimental designs
• Culture human fecal microbiota from ongoing cohort studies (e.g. BeBiCo on the development of the infant microbiome)
• Screen AsB transformation in these cultures
• Test realistic exposure scenarios and explore microbial determinants
• Reporting, paper writing, scientific presentations
• Participate in HPLC-ICP-MS troubleshooting among other tasks in the laboratory

The successful candidate should hold a PhD degree in Environmental or Analytical Chemistry or related field and have proven research experience in using hyphenated method. Independent use of HPLC-ICP-MS to measure trace element species in matrices other than water is a must. Someone with experience on arsenic speciation would be preferred. The successful candidate should have excellent English writing and communication skills and a proven track record of scientific presentations and publications. Other essentials skills include a strong team orientation, working in a precise, engaged and self-organized manner as well as commitment to work in an interdisciplinary field with multiple supervisors.

Specific experience in the following domains would be an asset:

• Statistics and data visualisation,
• Method development and/or troubleshooting in HPLC-ICP-MS,
• Microbiology
• Incubations.

Your Benefits

• International reputation
• Central location in the heart of Bern
• Meaningful work and fair compensation
• Collaborative environment and ambitious team

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