Identification of surfactant impacts on microbial glyphosate degraders in freshwater sediments

The international Doctoral Program Environment Water (ENWAT) of the Faculty of Civil and Environmental Engineering Sciences University of Stuttgart Germany in collaboration with the German Academic Exchange Service (DAAD) opens a call for max. 2 PhD positions for research in Environment Water. Each project involves high-quality research and state-of-the-art techniques and is supervised by excellent researchers. We are looking for highly motivated and talented students with a passion for science. Candidates must demonstrate an excellent performance in their previous academic education.

Title: Identification of surfactant impacts on microbial glyphosate degraders in freshwater sediments

Advisor:Prof. Dr. Sara Kleindienst

Research group / department: Department of Environmental Microbiology Institute for Sanitary Engineering Water Quality and Solid Waste Management (ISWA)

Keywords: microorganisms microbial community structure microbial activities cultivation microcosms herbicide formulations glyphosate

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 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.

References:

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Antier C. Kudsk P. Reboud X. Ulber L. Baret P. V. & Messan A. (2020). Glyphosate Use in the European Agricultural Sector and a Framework for Its Further Monitoring. Sustainability 12(14) Article 14. 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. R. Benbrook C. & Antoniou M. N. (2019). Insight into the confusion over surfactant co-formulants in glyphosate-based herbicides. Food and Chemical Toxicology 128 137145. J. F. Acosta-Corts A. G. Kumar S. & Kaushik G. (2017). Biological Limitations on Glyphosate R. Singh & S. Kumar (Eds.) Green Technologies and Environmental Sustainability (pp. 179201). Springer International Publishing. 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. W. Parus A. Homa J. Batycka M. Niemczak M. Woniak-Karczewska M. Trzebny A. Zembrzuska Dabert M. Tncsics A. Cajthaml T. Heipieper H. J. & Chrzanowski . (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. M. C. Allegrini M. Hernandez Guijarro K. Behrends Kraemer F. Morrs 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. H. Feng Y. Fan X. & Chen S. (2018). Recent advances in glyphosate biodegradation. Applied Microbiology and Biotechnology 102(12) . Tasks

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)

Further Prerequisites:

• Resume/CV showing the applicants background professional skills a list of publications and oral and poster presentations as well as additional achievements (scholarships awards etc.)
• . Dipl.-Ing. or equivalent degree in Civil Engineering Water Resources Management Environmental Engineering or related sciences
• . in Civil Engineering Water Resources Management Environmental Engineering or related sciences

Copies of Certificates and Transcripts including all undergraduate level certificates and university degrees. All documents which are not in English or in German must be accompanied by copies of a legally certified English translation (for the application we will accept copies; but please be aware that originals or legally certified copies will be needed for the final case any differences between the copies and the originals show up the application will be dismissed.)

Please make sure that the copies of the transcripts show not only the grades but also explain the home grades system (please add copy of the description of grade scale).

• At the time of nomination to the DAAD (Dec 2025) generally no more than 6 years should have passed since the last degree was gained.
• Only international (non-German) applicants can be accepted. At the time of nomination to the DAAD (Dec 2025) the candidate must not have been resident in Germany for more than the last 15 months.
• Unless native speaker: proficiency in English (e.g. TOEFL IELTS etc.) or proof that . and . programs were held in English.
• 2 Reference letters from university professors from the applicants home university issued during the last 2 years.
• Motivation letter describing the applicants work experience and research goals (1 page)
• Summary of all relevant information about the applicant (1 page) - please upload it in the slot designated for the third reference.

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: The PhD candidate will get the opportunity to be creative and innovative and to work on a challenging and interdisciplinary topic.