Job Offers

Introduction / Background: Wastewater treatment plants (WWTPs) are estimated to contribute 8 – 11% of the methane and 2.7% of the nitrous oxide global gas emissions. Methane and nitrous oxide are greenhouse gases (GHG) and are 27 and 273 times more potent than CO₂, respectively (Intergovernmental Panel On Climate Change (IPCC), 2023). Additionally, nitrous oxide is considered to be the major anthropogenic contributor to the depletion of atmospheric ozone (Gruber, Von Känel, et al., 2021). These GHG are produced in the WWTPs by the action of methanogenic, nitrifying, and denitrifying microorganisms with the latter two being integral parts of the wastewater treatment process. For example, previous studies have shown that a decrease in the number of nitrite-oxidizing bacteria could lead to an accumulation of nitrite in the system (Gruber, Niederdorfer, et al., 2021). Nitrite accumulation coupled with suboptimal aeration rates can induce the denitrification activity of ammonia-oxidizing bacteria, leading to higher production of nitrous oxide (Chen et al., 2018). There is also seasonal and diurnal variations in nitrous oxide emissions which are correlated with the accumulation of nitrite or suboptimal oxygen concentrations in the system, respectively (Daelman et al., 2013, 2015; Gruber, Von Känel, et al., 2021). Seasonal variations in methane emission rates also occur and appear to be positively correlated with seasonal changes in water temperature (Masuda et al., 2015). Understanding how changes in the composition and flow rates of incoming wastewater can affect microbial community dynamics in WWTP is of the utmost importance. This will allow us find potential solutions that could lead to the reduction of GHG emissions from the wastewater treatment process.

Research Environment: The newly established Department of Environmental Microbiology at the Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA) at the University of Stuttgart consists of an interdisciplinary, international, and dynamic team of environmental microbiologists, microbial ecologists, and chemists. The research group focusses on fundamental research with links to applied areas and studies topics related to microbial pollutant degradation. More information can be found on our webpage: https://www.iswa.uni-stuttgart.de/institute/em/. The PhD candidate will get the opportunity to be creative and innovative, and to work on a challenging and interdisciplinary topic.

Research goals:

• To unravel the seasonal microbial interactions between key microbial communities involved in the production of GHGs in WWTPs.
• To establish laboratory microcosms using labelled substrates to determine how changes in the microbial community and environmental parameters lead to changes in GHG emissions.
• To perform in situ experiments at the WWTP located in ISWA to study how control parameters can be optimized to minimize changes in the plant’s microbiota leading to reduced GHG emissions.

Methods to be used:

• Quantification of physicochemical parameters, substrates, and products (e.g., via HPLC, IC, GC-MS)
• Aerobic and anaerobic enrichment of WWTP microbial communities
• Electrochemical sensors to quantify dissolved nitrous oxide and other related parameters in the wastewater, FTIR to quantify GHG emissions
• 16S rRNA gene amplicon sequencing
• Metagenomic and metatranscriptomic sequencing
• Statistical analysis of the obtained data sets

Prerequisites:

• Solid background in molecular ecology and environmental microbiology
• Ability to work independently and in a team
• Excellent management and communication skills
• Highly motivated and committed to pursuing interdisciplinary research
• Very good computer and language skills (English)

References

Chen, X., Yuan, Z., & Ni, B.-J. (2018). Nitrite accumulation inside sludge flocs significantly influencing nitrous oxide production by ammonium-oxidizing bacteria. Water Research, 143, 99–108. https://doi.org/10.1016/j.watres.2018.06.025

Daelman, M. R. J., Van Voorthuizen, E. M., Van Dongen, L. G. J. M., Volcke, E. I. P., & Van Loosdrecht, M. C. M. (2013). Methane and nitrous oxide emissions from municipal wastewater treatment – results from a long-term study. Water Science and Technology, 67(10), 2350–2355. https://doi.org/10.2166/wst.2013.109

Daelman, M. R. J., van Voorthuizen, E. M., van Dongen, U. G. J. M., Volcke, E. I. P., & van Loosdrecht, M. C. M. (2015). Seasonal and diurnal variability of N2O emissions from a full-scale municipal wastewater treatment plant. Science of The Total Environment, 536, 1–11. https://doi.org/10.1016/j.scitotenv.2015.06.122

Gruber, W., Niederdorfer, R., Ringwald, J., Morgenroth, E., Bürgmann, H., & Joss, A. (2021). Linking seasonal N2O emissions and nitrification failures to microbial dynamics in a SBR wastewater treatment plant. Water Research X, 11, 100098. https://doi.org/10.1016/j.wroa.2021.100098

Gruber, W., Von Känel, L., Vogt, L., Luck, M., Biolley, L., Feller, K., Moosmann, A., Krähenbühl, N., Kipf, M., Loosli, R., Vogel, M., Morgenroth, E., Braun, D., & Joss, A. (2021). Estimation of countrywide N2O emissions from wastewater treatment in Switzerland using long-term monitoring data. Water Research X, 13, 100122. https://doi.org/10.1016/j.wroa.2021.100122

Intergovernmental Panel On Climate Change (IPCC). (2023). Climate Change 2021 – The Physical Science Basis: Working Group I Contribution to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (1st ed.). Cambridge University Press. https://doi.org/10.1017/9781009157896

Masuda, S., Suzuki, S., Sano, I., Li, Y.-Y., & Nishimura, O. (2015). The seasonal variation of emission of greenhouse gases from a full-scale sewage treatment plant. Chemosphere, 140, 167–173. https://doi.org/10.1016/j.chemosphere.2014.09.042

Introduction / Background: Glyphosate is the most widely applied herbicide on Earth and accounts for 92% of the herbicide global use (Antier et al., 2020). In Europe, 25 – 64% of annual crop acreage was treated with glyphosate (Antier et al., 2020). This compound and its degradation by-products (mainly aminomethylphosphonic acid; AMPA) exhibit potential toxicity for the microbial communities as well as for humans (Wei et al., 2024; Zhan et al., 2018). Improper application of glyphosate causes its accumulation in terrestrial and aquatic environments as glyphosate can bind to soil particles leading it to be found in the upper soil layer and in freshwater sediments in proximity to agricultural fields (Zhan et al., 2018). Glyphosate is not used as single compound but as mixture, a formulation, with surfactants as the second most abundant ingredient (Villarreal-Chiu et al., 2017). While these surfactants are considered inert in terms of their effect on glyphosate efficacy (Mesnage et al., 2019), a critical knowledge gap exists regarding their impacts on microorganisms in the environment (Zabaloy et al., 2022). Previous studies show mixed results on the effects of surfactants on glyphosate biodegradation. For example, one study showed that a surfactant (Triton CG-110) has no effect on glyphosate mineralisation (Carretta et al., 2020), but a different kind of surfactant (quaternary ammonium cations) decreased glyphosate mineralization rates (Wilms et al., 2023).

The PhD project will identify glyphosate-based surfactant impacts on microorganisms from freshwater sediments, e.g., rivers or ponds, that are capable of degrading glyphosate. In particular, aerobic and anaerobic cultivation techniques will be used to enrich and isolate the target organisms. Subsequently, cultivation experiments will be used to unravel surfactant impacts on isolated microbial key players. Microcosm studies will be performed to identify surfactant impacts on complex microbial communities in freshwater sediments using a suite of biogeochemical and molecular tools (e.g., 16S rRNA gene sequencing, metagenomics, and metatranscriptomics). These interdisciplinary studies will further reveal if surfactants from glyphosate application can have effects on glyphosate persistence in the environment.

Research Environment: The Department of Environmental Microbiology at the Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA) at the University of Stuttgart consists of an interdisciplinary, international, and dynamic team of environmental microbiologists, microbial ecologists, and chemists. The research group focuses on fundamental research with links to applied areas and studies topics related to microbial pollutant degradation. More information can be found on our webpage: https://www.iswa.uni-stuttgart.de/institute/em/. The PhD candidate will get the opportunity to be creative and innovative, and to work on a challenging and interdisciplinary topic.

Research goals:

• To unravel the interactions between surfactants present in glyphosate formulations and key freshwater sediment microorganisms involved in glyphosate biodegradation.
• To enrich and isolate novel microorganisms that drive glyphosate and AMPA biodegradation in the presence and absence of surfactants.
• To establish laboratory microcosms and to determine how surfactants change the microbial community of freshwater sediments and their ability to metabolize glyphosate and AMPA.

Methods to be used:

• Aerobic and anaerobic enrichment of glyphosate-degrading freshwater sediment microbial communities and isolates

• Quantification of physicochemical parameters, substrates, and products (e.g., via HPLC, IC, GC-MS)

• 16S rRNA gene amplicon sequencing
• Metagenomic and metatranscriptomic sequencing
• Statistical analysis of the obtained data sets

Prerequisites:

• Solid background in molecular ecology and environmental microbiology
• Ability to work independently and in a team
• Excellent management and communication skills
• Highly motivated and committed to pursuing interdisciplinary research
• Very good computer and language skills (English)

References

Antier, C., Kudsk, P., Reboud, X., Ulber, L., Baret, P. V., & Messéan, A. (2020). Glyphosate Use in the European Agricultural Sector and a Framework for Its Further Monitoring. Sustainability, 12(14), Article 14. https://doi.org/10.3390/su12145682

Carretta, L., Cardinali, A., Masin, R., Zanin, G., & Cederlund, H. (2020). Decyl glucoside surfactant Triton CG-110 does not significantly affect the environmental fate of glyphosate in the soil at environmentally relevant concentrations. Journal of Hazardous Materials, 388, 122111. https://doi.org/10.1016/j.jhazmat.2020.122111

Mesnage, R., Benbrook, C., & Antoniou, M. N. (2019). Insight into the confusion over surfactant co-formulants in glyphosate-based herbicides. Food and Chemical Toxicology, 128, 137–145. https://doi.org/10.1016/j.fct.2019.03.053

Villarreal-Chiu, J. F., Acosta-Cortés, A. G., Kumar, S., & Kaushik, G. (2017). Biological Limitations on Glyphosate Biodegradation. In R. Singh & S. Kumar (Eds.), Green Technologies and Environmental Sustainability (pp. 179–201). Springer International Publishing. https://doi.org/10.1007/978-3-319-50654-8_8

Wei, X., Pan, Y., Zhang, Z., Cui, J., Yin, R., Li, H., Qin, J., Li, A. J., & Qiu, R. (2024). Biomonitoring of glyphosate and aminomethylphosphonic acid: Current insights and future perspectives. Journal of Hazardous Materials, 463, 132814. https://doi.org/10.1016/j.jhazmat.2023.132814

Wilms, W., Parus, A., Homa, J., Batycka, M., Niemczak, M., Woźniak-Karczewska, M., Trzebny, A., Zembrzuska, Dabert, M., Táncsics, A., Cajthaml, T., Heipieper, H. J., & Chrzanowski, Ł. (2023). Glyphosate versus glyphosate based ionic liquids: Effect of cation on glyphosate biodegradation, soxA and phnJ genes abundance and microbial populations changes during soil bioaugmentation. Chemosphere, 316, 137717. https://doi.org/10.1016/j.chemosphere.2022.137717

Zabaloy, M. C., Allegrini, M., Hernandez Guijarro, K., Behrends Kraemer, F., Morrás, H., & Erijman, L. (2022). Microbiomes and glyphosate biodegradation in edaphic and aquatic environments: Recent issues and trends. World Journal of Microbiology and Biotechnology, 38(6), 98. https://doi.org/10.1007/s11274-022-03281-w

Zhan, H., Feng, Y., Fan, X., & Chen, S. (2018). Recent advances in glyphosate biodegradation. Applied Microbiology and Biotechnology, 102(12), 5033–5043. https://doi.org/10.1007/s00253-018-9035-0

The Department of Environmental Microbiology at the Institute for Sanitary Engineering, Water Quality and Solid Waste Management (ISWA) at the University of Stuttgart is delighted to announce an open ERC-funded position for a Postdoctoral Researcher (1.5 years) who will work on:

“Identification of surfactant impacts on N- and C-cycling microbial key players in soils and freshwater sediments”

Glyphosate is the most widely applied herbicide on Earth, exhibits potential toxicity, and persists in the environment. Glyphosate is not used as single compound but as mixture, a formulation, with surfactants as the second most abundant ingredient. These surfactants are considered inert, and a critical knowledge gap exists regarding their impacts on microorganisms in the environment. Specifically, those capable of glyphosate degradation and on microbial key players that drive biogeochemical cycles and influence the fate of greenhouse gases.

The postdoc project will identify glyphosate-based surfactant impacts on microbial key players that are involved in the N- and C-cycle (e.g., nitrifiers or heterotrophic C-cyclers). In particular, the postdoc will assist PhD students in the execution of a large-scale microcosm experiment where both oxic and anoxic conditions will be tested with the various herbicides and surfactants. Following this, the postdoc will examine the data generated by the PhD student and conduct overview statistically analyses to determine the broader impacts of the surfactants on the N- and C-cycling microorganisms. Finally, the postdoc will organize and lead a field study, using the knowledge generated by the PhD student, to assess the impact of the glyphosate-based herbicide surfactants in situ. Molecular biological (i.e., 16S rRNA amplicon and omics sequencing and qPCR) and chemical (e.g., gas and surfactant measurements) data will be generated throughout these steps. These interdisciplinary studies will further reveal if surfactants from glyphosate application can have effects on glyphosate persistence in the environment and on greenhouse gas formation. The project is funded by the European Research Council (ERC).

We are offering one postdoctoral position (1.5 years) in an interdisciplinary, international, and dynamic team of environmental microbiologists and microbial ecologists. This position provides the opportunity for the candidate to be creative and innovative, and to work on a challenging topic that combines various fields within environmental sciences. Ideal candidates should have a PhD in microbiology with solid background in environmental microbiology and molecular biology. Furthermore, candidates should demonstrate strong leadership qualities and have field experience that would allow them to lead a field study. Applicants must have the ability to work both independently and in a team, have excellent management and communication skills, and should be highly motivated and committed to pursuing interdisciplinary research. Very good computer and English language skills are necessary. The candidates will have the opportunity to present their results in international journals and conferences.

The starting date is October 2025 or as soon as possible thereafter. Employment (1.5 years, TV-L E 13, 100%) will be arranged by the administration of the University of Stuttgart. People with disabilities will be given preferential consideration if they are equally qualified. The University of Stuttgart strives to increase the proportion of women in research and teaching and therefore strongly encourages qualified women to apply.

Applications including CV, motivation letter, summary of research and teaching experience, publication list, an overview about the methods used in the past, and contact information of academic references should be uploaded via JoinUs Universität Stuttgart application system before July 31st, 2025.
Questions about the announced position can be addressed to Dr. Katharine Thompson, Email: katharine.thompson@iswa.uni-stuttgart.de