People

Prof. Dr. Marco Keiluweit (he/him, PI)
Marco is an Associate Professor and the PI of the Soil Biogeochemistry Group in the Faculty of Geosciences and the Environment (FGSE) at the University of Lausanne (Switzerland). Since his years as a BSc student, Marco has been interested in the molecular mechanisms that underlie soil function, and its response to climate change.  He received his BSc in Geoecology fom the University of Tübingen (Germany) as well as MSc and PhD degrees in Soil Biogeochemistry from Oregon State University (USA). During his PhD, Marco worked as a Lawrence Scholar in the Isotope Signature Group at Lawrence Livermore National Laboratory (USA). After defending his dissertation in 2013, he joined the Environmental & Soil Biogeochemistry group at Stanford University (USA) as a Postdoctoral Scholar between 2014 and 2015. Marco became Assistant Professor of Soil Biogeochemistry at the University of Massachusetts-Amherst in 2016, before moving his group to UNIL in 2022.  

Dr. Luis Colocho (he/him, Senior Scientist)
Luis is a Senior Scientist in Analytical Biogeochemistry. He received his Dr. rer. nat. in Biogeochemistry from the Technical University of Munich (Germany), following a M.Sc. in Soil Science and a B.S. from the Federal University of Viçosa (Brazil).  Thereafter, he conducted his postdoctoral research at the beamline ID21 of the European Synchrotron Radiation Facility (ESRF), and served as a Beamline Scientist at the beamline I08 of Diamond Light Source (UK), before moving to UNIL in 2025. He aims to understand how biological actors—plants, microbes, and humans—shape soil geochemistry and ecosystem function. He draws from his experience at large-scale research facilities to integrate cutting-edge microspectroscopic techniques to interrogate the molecular-scale interactions at soil interfaces.  

Dr. Jill Bachelder (she/her, postdoc) 
Jill joined the Soil Biogeochemistry group as a postdoctoral researcher in September 2025. She holds a B.Sc. in Chemistry from McGill University and an M.Sc. in Chemistry from the University of Montreal. Jill completed her doctorate in the group of plant nutrition at ETH Zürich, followed by a postdoc at the Helmholtz Centre for Environmental Research (UFZ Leipzig). During her time in the Soil Biogeochemistry group, Jill will be investigating how limited nutrient availability and plant-soil-microbial interactions affect mineral-associated organic matter in degraded tropical pasture soils from the Colombian Orinoquía. 

Dr. Zhengzheng Chen (she/her, postdoc)
Zhengzheng joined the Soil Biogeochemistry group in May 2026.
She did her doctoral research with Prof. Liane Benning at the Helmholtz Centre for Geoscience (GFZ), where she dived into the iron world of iron minerals—from nanoparticle characterization to digging up soils in Iceland. She loves illustrating the interaction between iron and carbon cycling using chemical approaches and synchrotron techniques. For her postdoc at UNIL, she extends this work into plant systems, studying how iron, carbon, and sulfur interact in the rhizosphere to help explain carbon dynamics in coastal marshes under oscillating tidal conditions.

Dr. Megan Foley (she/her, postdoc)
Megan joined the Soil Biogeochemistry group in November 2024. She received her PhD in Biology from Northern Arizona University (USA) where she studied environmental and evolutionary controls over microbial growth in soil. Megan is interested in how microbe-mineral interactions affect organic carbon cycling in soils. During her PhD, Megan was awarded a National Science Foundation Graduate Student Research Program fellowship and worked in the Environmental Isotope Systems Group at Lawrence Livermore National Laboratory (USA) as a Department of Energy Graduate Student Research Fellow.

Philip Gwyther (he/his, PhD student)
Philip joined the Soil Biogeochemistry group in July 2024. He became interested in microbial biochemistry during his BSc in Molecular Biology at the University of Sheffield, working on metabolic modeling and bacterial detoxification projects. He completed his MSc in Integrative Biology at the University of Lausanne, where his thesis focussed on the role of niche availability in soil inoculant persistence. As an SNSF Junior Researcher, he used deep learning to analyze the cytometric diversity of soil microbiota. In his PhD, Philip will investigate how tidal and diel cycles drive redox conditions and microbial metabolism in salt marsh soils and their subsequent impacts on carbon cycling in the system. 

Junna Frei (she/her, PhD student)
Junna received her MSc in Biology at the University of Neuchâtel specializing in Sustainable Agriculture and Chemical Ecology. During her thesis on biorecovery of phosphorus from digested sewage sludge using basidiomycetes, she developed a strong interest in mycology, particularly in the ability of fungi to recover nutrients from their substrate. At UNIL, she is involved in a research experiment aimed at determining the impact of changes in rainfall intensity on the dynamics of mineral-organic associations in the rhizosphere. She is particularly interested in investigating how fungi affect mineral-organic associations.

Samuel Steiner (he/him, PhD student)
Samuel, from Basel, Switzerland, joined the group as a PhD candidate in August 2023. He works on a joint project between Agroscope and the University of Lausanne, investigating the effects of fertilization and soil quality on organic matter retention and nitrogen use efficiency in croplands. Before starting his PhD, Samuel worked in the private sector, focusing on agroforestry and certification in cocoa production, as well as a sustainable rice intensification project in Senegal. He holds a Master's degree in Agricultural Sciences from ETH Zurich, where he specialised in plant nutrition and rhizodeposition.
Samuel is passionate about the global challenges of food security and climate change, aiming to empower producers with tools and insights for climate-smart farming. He is fascinated by the trade-offs in agriculture—balancing productivity, environmental health, and societal needs—making it a unique intersection of natural and social sciences.

Bouke Bentvelsen (she/her, PhD student)
Bouke joined the Soil Biogeochemistry group as a PhD student in November 2024. She holds a degree in Biomedical Sciences from the University of Amsterdam. Initially involved in a collaborative project connecting cancer research and developmental biology, she found herself more interested in the environment than in humans. It led her to environmental microbiology, where, as an SNSF researcher, she worked a project aimed to identify and classify soil bacterial species using live cell imaging data. Now, in her PhD, she wants to better understand organic matter dynamics in soil, with a specific focus on the role of soil bacteria. Soil microbial communities affect both carbon retention and release in the soil, with bacterial necromass playing a significant role in carbon persistence. Her research focuses on the microenvironments controlling necromass formation and persistence.