Fachgebiet Wasserreinhaltung
Studium und Lehre
Abschlussarbeiten
Masters Thesis: Modeling phototroph – heterotroph cross feeding
Phytoplankton release dissolved organic matter (DOM), a process traditionally viewed as unintentional and a disadvantage (i.e. loss of biomass). Recent observations suggest that phytoplankton purposefully produce/release DOM to support bacteria growing around them. Further, different phytoplankton species produce different DOM compounds that may attract specific bacteria that can perform a beneficial function (e.g. fix nitrogen). This mechanism is a missing link in our understanding of phytoplankton ecology and models, and limits our ability to manage harmful cyanobacteria blooms.
The purpose of this thesis project is to develop a mathematical model of the cross-feeding process. An existing AQUASIM model of Lake Zürich will be modified/extended to include the production of different DOM species, and a number of heterotrophic bacteria that specialize on these compounds. Model results will be compared to observed time series of phytoplankton species, DOM characteristics and heterotrophic species.
Contact Ferdi Helleger: ferdi.hellweger(at)tu-berlin.de, KF 306
Bachelor-/Masterarbeit: Priority effects of bacterial associations to phytoplankton
Interactions between phytoplankton and bacteria are crucial for the functioning of aquatic systems and biogeochemical cycles at a global scale. Most of these interactions, however, take place at the surface of the phytoplankton cell, which offers limited space.
In ecology, the “priority effect” implies that a species benefits as a result of its prior arrival at a site, i.e. first come, first serve. The concrete mechanisms underlying the priority effect in phytoplankton-bacteria associations, however, are yet unknown. The aim of the Bachelor/Master thesis is to add experimental support to the proposed priority effect for phytoplankton-bacteria associations, and to gain insights on the underlying mechanisms. For this, two different bacterial strains that own similar growth rates will be sequentially added to an axenic (i.e. bacteria free) phytoplankton culture, and the priority effects analyzed by 16S rDNA sequencing. The obtained experimental results will be compared to outcomes of a model simulating phytoplankton-bacteria associations (including priority effects) which was developed by Prof. Ferdi Hellweger.
The student will perform experiments, sampling and (partly bioinformatic) analysis.
The student should be interested in aquatic microbial ecology, and familiar with Excel. Ideally, the student has experience in lab work (pipetting, use of a clean bench, etc), but this is not mandatory. Necessary skills will be taught during the project. If you are interested in the topic please contact Dr. Falk Eigemann: eigemann(at)tu-berlin.de.
The student is very welcome to add own ideas or suggestions to the project.
Bachelor-/Masterarbeit: Why and when is it beneficial for heterotrophic bacteria to leave their phytoplankton host
Phytoplankton fix carbon dioxide, and subsequently release the synthesized compounds as dissolved organic matter, which becomes processed and recycled by heterotrophic bacteria. Bacteria, for their part, provide e.g. vitamins to the phytoplankton. Such phytoplankton-bacteria interactions are crucial for the functioning of aquatic systems and biogeochemical cycles at a global scale.
The BA/MA thesis will experimentally examine two mechanisms that potentially benefit the bacterium due to decreased loss rates in phytoplankton-bacteria associations.
i) Do bacteria detach from their phytoplankton host at night to avoid zooplankton predators?
Background: Zooplankton performs a diel vertical migration, i.e. at daytimes the zooplankton stays in the deep, whereas at night the zooplankton migrates to the surface. Thereby, zooplankton hides during the day from predators (mostly fish) that rely on light to sense their prey, and swim up at night (when light is scarce), to feed on phytoplankton. However, the zooplankton may not only feed on the phytoplankton, but also on phytoplankton associated bacteria. Consequently, a detachment of bacteria from their phytoplankton host at night may decrease the loss rate of bacteria. To test this, phytoplankton will be cultured at day/night cycles with defined bacterial strains, and the diel ratio of attached to detached bacteria determined by fluorescence microscopy.
ii) Do bacteria kill their phytoplankton host when it gets sick and/or old to leave a “high risk environment”?
Background: Interactions between phytoplankton and bacteria sometimes switch from symbioses into pathogenicity if the phytoplankton host becomes senescent, due to chemicals rendered by the bacterium. Why the bacteria kill their phytoplankton hosts, however, is not known in detail. To gain insight on potential benefits of killing your host, a bacterial strain that kills its phytoplankton host as well as a mutant of the same strain lacking this feature will be cultured together with the phytoplankton host, and processes that may explain why killing your host is a beneficial trait will be mimicked.
The obtained experimental results of both experiments will be compared to outcomes of a model simulating phytoplankton-bacteria associations (including diel detachment and attachment, as well as switches from symbiosis to pathogenicity) which was developed by Prof. Ferdi Hellweger.
The student will perform lab work (experiments, sampling), and subsequent (partly bioinformatic) analyses of the experiments.
The student should be interested in aquatic microbial ecology, and familiar with Excel. Ideally, the student has experience in lab work (pipetting, use of a clean bench, etc), but this is not mandatory. All necessary skills will be taught during the project. If you are interested in the topic please contact Dr. Falk Eigemann: eigemann(at)tu-berlin.de.
The student is very welcome to add own ideas or suggestions to the project.
Bachelor-/Masterarbeit: Haben stärker verwandte Mikroorganismen eine ähnlichere Fitness? Wie stark ist der Zusammenhang zwischen phylogenetischer Distanz und ökologischer Fitness in verschiedenen Bakterienfamilien?
Mikroorganismen werden heutzutage typischerweise durch Sequenzierung von Markergenen, wie z.B. der 16S rRNA, identifiziert, die dann mit Datenbanken abgeglichen werden, um die Sequenz einer Spezies zuzuordnen.
Manche Sequenzen, die phylogenetisch stärker verwandter Spezies, sind sich sehr ähnlich und unterscheiden sich nur durch wenige Nucleotide. Vergleicht man hingegen nur schwach Verwandte Spezies, sind die Unterschiede der Sequenzen größer. Maß hierfür ist die sogenannte „Average Nucleotide Distance“, kurz AND.
Lassen sich aus dieser AND, also der phylogenetischen Distanz, Schlussfolgerungen ziehen wie ähnlich sich die Spezies in einem Ökosystem Verhalten? Ob sie gleichzeitig vorkommen?
Aktuelle Ergebnisse deuten darauf hin, dass ein Zusammenhang besteht, der augenscheinlich in einigen Familien größer ist, als in anderen.
Ob dem tatsächlich so ist soll anhand hochauflösender Zeitreihendaten analysiert werden. Ein solches Datenset steht bereits zur Verfügung, weitere können/sollen im Rahmen der Arbeit (je nach Umfang, Bachelor- oder Masterarbeit) recherchiert werden.
Bei Interesse meldet euch gerne per E-Mail bei Jutta Hoffmann: jutta.hoffmann(at)tu-berlin.de
Master Thesis: Magnetic iron oxide nanoparticles (MNP) as surrogate for nanoscale contaminants in drinking water treatment systems
Many substances in water are in the nanometer to micrometer range, such as humic substances, viruses
or bacteria. Because of their relatively small size, there are risks of incomplete retention in physical
barriers, such as rapid sand filters and membranes. Analytical methods for nanoscale contaminants vary
from case to case and often require extensive lab work and time. In addition, there is still a lack of a
holistic description between the size of nanoscale contaminants and the effectiveness of physical
removal. Are there fast methods to characterize the fate of nanoscale contaminants? Can we manipulate
test particles to mimic the behavior and retention of complex particles? Magnetic iron oxide magnetic
nanoparticles (MNP) might be a valuable option due to their very fast and pragmatic detection.
Magnetic iron oxide nanoparticles (MNP) typically consist of magnetite (Fe3O4) or maghemite (γ-Fe2O3)
cores with sizes ranging from 1 to 100 nm [1]. They have many important properties, such as modifiable
surfaces, biocompatibility and high magnetic susceptibility [2], which contribute to their wide
applications in biotechnology such as biosensing, diagnostic imaging, gene therapy, cell labeling,
transplant monitoring, etc. [3]. Many researches have proved efficient synthesis routes of sizecontrolled MNP with narrow size distributions [4], and different MNP systems and specific physical
properties are commercially available. MNP can be quickly quantified by deploying photometry and
magnetic techniques such as magnetic particle spectroscopy [5] and magnetorelaxometry [6]. These
characteristics provide a basis for applying MNP in water treatment research.
In this master thesis, potentials of MNP-based test procedures in the water treatment field shall be
explored. Your tasks could include:
Characterizing the physical properties of magnetic iron oxide nanoparticles of different sizes
Analyzing the fate of magnetic iron oxide nanoparticles in column systems for drinking water treatment
Tracing the fate of magnetic iron oxide nanoparticles in membrane filtration
Comparing the fate of MNP with nanoscale contaminants such as bacteria and plasmids in column and membrane filtration systems
The laboratory work will be carried out in different research institutions in Berlin, including
Umweltbundesamt (UBA), TU Berlin and Physikalisch-Technische Bundesanstalt (PTB).
If you are interested, please contact Ms. Lizhi Zhao: lizhi.zhao(at)uba.de
Section of Drinking Water Treatment, Umweltbundesamt (UBA)
Chair of Water Treatment, Technische Universität Berlin (KF 4)
Telephone: 030-8903-3121
Praktikum / Bachelor- / Masterarbeit: Abwasserwiederverwendung zur Grünflächenbewässerung. Bewertung mikrobiologischer Parameter mittels Durchflusszytometrie
Die Wiederverwendung von gereinigtem Abwasser bietet Möglichkeiten, mit der vielerorts bereits akuten Wasserknappheit besser umzugehen, beispielsweise durch regional verringerten Frischwasserverbrauch. Im Zuge von Feldversuchen zur Bewässerung von landwirtschaftlichen Flächen und Grünflächen mit behandeltem Abwasser führt das Umweltbundesamt umfangreiche Analysen durch. Ziel ist es, die damit verbundenen Risiken zu bewerten und Empfehlungen für die Implementierung der Wasserwiederverwendung zu erarbeiten.
Bei der Bewässerung von öffentlichem Grün stellt die Exposition gegenüber abwasserbürtigen Pathogenen ein Risiko dar. Die Anwendbarkeit von Durchflusszytometrie mit fertigen Testkits zur Ermittlung der Keimbelastung nach Bewässerungsereignissen soll hierfür untersucht werden. Sowohl Zeitreihen der Keimbelastung, als auch der Vergleich zu Standardmethoden sind dabei von Interesse.
Arbeitsumfang und Fragestellungen können je nach angestrebter Arbeit angepasst werden. Vorzugsweise wird eine Bachelorarbeit oder ein Praktikum absolviert.
Bei Interesse und Fragen bitte Kontakt aufnehmen:
E-Mail: pascal.hasselder(at)uba.de
Tel.: +49 (0) 030 8903-4088
Masterarbeit: Abwasserwiederverwendung zur Bewässerung in der Landwirtschaft. Eine Risikoanalyse aus der Praxis für die Praxis
Die Wiederverwendung von gereinigtem Abwasser bietet Möglichkeiten, mit der vielerorts bereits akuten Wasserknappheit besser umzugehen, beispielsweise durch regional verringerten Frischwasserverbrauch. Im Zuge von Feldversuchen zur Bewässerung von landwirtschaftlichen Flächen und Grünflächen mit behandeltem Abwasser führt das Umweltbundesamt umfangreiche Analysen durch. Ziel ist es, die damit verbundenen Risiken zu bewerten und Empfehlungen für die Implementierung der Wasserwiederverwendung zu erarbeiten.
Für eine umfassende Risikoanalyse ist es notwendig die relevanten Systemparameter zu erfassen, d.h. die Ausgangssituation muss beschrieben und mögliche Veränderungen überwacht werden. Ein Schwerpunkt dabei wird sein, den Transfer von Spurenstoffen aus dem Bewässerungswasser in Boden und Grundwasser sowie in die Pflanzen zu analysieren. Die Abschlussarbeit bietet Dir die Möglichkeit eine vielseitige Fragestellung, anhand eines konkreten Beispiels, mit Methoden der Umweltanalytik zu beantworten.
Bei Interesse und Fragen gerne Kontakt aufnehmen:
E-Mail: pascal.hasselder(at)uba.de
Tel.: +49 (0) 030 8903-4088
Master Thesis beim UBA: Anoxic microbial transformation of antibiotics
Exact title: Anoxic transformation of sulfonamide antibiotics by sulfate-reducing bacteria
The job
The group “Anoxic transformation” in the Department of Environmental Biotechnology is offering a master thesis for six months in “Anoxic microbial transformation of antibiotics” with expected start in December 2023 or January 2024, ideally in combination with a three months internship in the same group.
Current water infrastructure is not adequately equipped to meet the challenge of nowadays water contaminations and render sufficient removal in wastewater treatment plants (WWTPs). The global overconsumption of antibiotics, their persistency in WWTPs and occurrence in the environment lead to the propagation of antibiotic resistant bacteria and antibiotic resistance genes. Sulfonamide antibiotics (SAs) in combination with the antibiotic trimethoprim are one of the most prescribed antibiotics in livestock farming and are frequently detected in WWTPs effluents, aqueous environments, manure and even groundwater (Kümmerer, 2009). Due to the incapability of aerobic techniques in WWTP to sufficiently remove SAs from water (Verlicchi et al., 2012a, b), researchers focused on anaerobic techniques emphasizing the suitability of sulfate reducing conditions and sulfate-reducing bacteria (SRB) to transform SAs and reduce their environmental persistency (Köpke et al., in preparation).
However, the knowledge in regard to the molecular process of SA transformation by SRBs and the role of their reductive transformation in the sulfate reducing metabolism is limited to only a few studies (Ouyang et al., 2021). The extent to which SRBs can transform sulfonamides and chemically similar antibiotics, also under reduction of other electron acceptors is not elucidated yet. The following specific objectives are supposed to be investigated within the master thesis: A) investigate the anaerobic transformation of other SAs and trimethoprim than SMX and their metabolites by pure strains of sulfate-reducing bacteria; B) test the capability of SRBs to reductively transform isoxazole moiety-containing antibiotics other than SMX; C) test the capability of SRBs to reductively transform SAs while respiring alternative terminal electron acceptors then sulfate.
Overall, the described work will enhance the understanding of relevant natural attenuation processes of SAs, trimethoprim and other antibiotics in the environment. It will help to elucidate the favourable conditions and proposes responsible organisms ideally rendering these concerning micropollutants less recalcitrant and consequently reducing the risk of antibiotic resistance propagation in the environment.
Your tasks
- Conduct various anaerobic cultivation experiments testing one pure strain of SRBs in combination with different sulfonamides, trimethoprim and other antibiotics
- Apply different analytical techniques including ion chromatography (monitor sulfate consumption), spectral photometry (monitor sulfide generation, optical density), and high-performance liquid chromatography (HPLC; determination of organic substrates)
- Prepare liquid chromatography - tandem mass spectrometry (LC-MS/MS) samples following analytical quality standards and procedures
- Analyse, process and illustrate LC-MS/MS derived data
- Summarize, illustrate and discuss obtained experimental data with your supervisors on a regular basis
- Plan and conduct follow-up experiments in correspondence with your supervisors.
- Write and submit a master thesis.
We offer
- Excellent technical facilities and the opportunity to learn and routinely apply various analytical devices
- A very open-minded and interdisciplinary work environment of (micro)biologist, biochemist, environmental engineers and biotechnologists from various countries
- The chance to learn various anaerobic workflows and techniques
- A very high degree of flexibility, self-organization and independence in correspondence with you supervisors
- Opportunity to develop, test and pursue your own ideas and interests within the project
- A vibrant and young city with a high quality of life, cultural offerings and easy access to natural surroundings
Your profile
- Practical experience in (preferably anaerobic) microbiology, biotechnology, environmental engineering or sciences or equivalent fields
- Interest in an interdisciplinary project and work environment
- Experiences in independently planning and conducting laboratory experiments and deriving conclusion from them
- Proficient English for a scientific environment
If you are interested, please contact:
Mr. Jimmy Köpke
Doctoral student
Department Environmental Biotechnology
Helmholtz Centre for Environmental Research UFZ Leipzig
Permoserstraße 15, 04318 Leipzig
Email: jimmy.koepke(at)ufz.de
References
Kümmerer, K., 2009a. Antibiotics in the aquatic environment – A review – Part I. Chemosphere 75, 417–434. doi.org/10.1016/j.chemosphere.2008.11.086
Bachelorarbeit FG Wasserreinhaltung, Umweltchemie und Luftreinhaltung: Entwicklung und Bau einer kleinen Versuchsanlage für die Bildung von See-Aerosolen
Die Fachgebiete „Wasserreinhaltung“ und „Umweltchemie und Luftreinhaltung“ planen die Ausbreitung von an Aerosolen gebundenen Cyanotoxinen quantitativ zu erfassen. Diese Thematik ist aufgrund der häufigeren Entwicklung von Algen- bzw. Cyanobakterienblüten durch den Klimawandel von großer Bedeutung, da eine Inhalation der „beladenen“ Aerosole in Gewässernähe möglich ist. Es kann nicht ausgeschlossen werden, dass die Inhalation gesundheitsgefährdend sein kann, wenn z.B. das Nervengift Anatoxin-a aerosolgebunden inhaliert wird.
Die Methodenentwicklung, die die Erzeugung und Sammlung von Aerosolen sowie die quantitative Bestimmung ausgewählter organsicher Verbindungen an den Aerosolen beinhaltet, soll zunächst im Labor mit ausgewählten nicht toxischen organischen Spurenstoffen erfolgen.
Im Rahmen der Bachelorarbeit soll zunächst ein Versuchsaufbau zur Erzeugung von See-Aerosolen entwickelt und gebaut und erste Versuche zum quantitativen Nachweis von aerosolgebunden Verbindungen durchgeführt werden.
Beginn: nach Absprache
Betreuer: Dr. Anke Putschew, Prof. Held, Prof. Hellweger
September 2023