Members & Current Projects
Microbial Ecology Group Members
We are highly interested in topics related to Microbial Ecology of pelagic and benthic marine as well as freshwater aquifer communities. Our research employs cutting-edge techniques (e.g. stable-isotope probing, Omics, Nanometer-scale Secondary Ion Mass Spectrometry) to identify microbial key-players within diverse microbial communities, to determine microbial activities and its limiting and stimulating factors, to unravel metabolic pathways, and to shed light on the fate of pollutants in the environment.
Around 30 % of freshwater on Earth occurs as groundwater stored in aquifers, which are valuable sources of drinking water. However, anthropogenic activities such as fertilizer and pesticide application to agricultural land can have deleterious effects on the quality of the groundwater resulting in elevated concentrations of harmful pollutants. My research uses in-situ microcosms deployed in groundwater wells to characterize the microbial community and identify active microbes involved with pollutant turnover. The genomic potential and capabilities of these crucial microbes will also be investigated by applying omics techniques such as metagenomics, metatranscriptomics and metaproteomics.
Human activity in urban and rural areas has resulted in diffuse pollution of anthropogenic contaminants across the environment. Despite decades of research, serious knowledge gaps exist concerning the fate of these compounds on the landscape scale and their impact on water quality, ecology, and human health. My research will focus on the assessment of microbial pathways of pollutant turnover (e.g. nitrate, pesticides) in contrasting landscape elements (rivers, sub-catchments, floodplains, aquifers and soils) in the catchment area of River Ammer in Germany. A variety of molecular-biological tools will be used to achieve this goal, such as qPCR, amplicon sequencing, and cutting edge meta-omics techniques.
Diffuse pollution of soils, surface waters, and ground-water by a multitude of anthropogenic organic and inorganic compounds is a growing global concern. To shed light on the fate and behavior of these pollutants on the landscape scale microbial pollutant turnover will be examined by applying 16S amplicon sequencing, metagenomics, metatranscriptomics, and metaproteomics to field samples. I will focus on the management and integrative bioinformatics analyses of omics data sets of environmental samples. The aim is to identify major microbial players in pollutant degradation and the underlying molecular processes.
As technician my main duty is the organization of lab structure including the instruction of new students and postdocs, maintenance of instruments, monitoring and updating of SOPs and preparation of standardized buffers and solutions. In addition I supervise Bachelor and Master Students and support PhD students and Postdocs e.g. in the optimization of DNA extraction methods, the development of qPCR assays or in the preparation and completion of field sampling campaigns.
Small-scale oil pollution events, i.e. diffuse inputs, contribute to greater extends to global anthropogenic oil contamination than large-scale pollution events. To elucidate this major environmental thread on marine ecosystems, the response of marine microbiomes to small-scale pollution scenarios will be studied. For this, I will evaluate a molecular-biological method to characterize microbial seawater communities by their potential and actual hydrocarbon degrading properties. Subsequently, pure cultures, microcosms, and field samples will be studied to quantify hydrocarbon degradation rates, determine rate-influencing factors, identify microbial key players, and elucidate metabolic pathways.
Microbial iron(II) oxidation plays an important role for the fate of many contaminants (e.g., arsenic) and nutrients in the environment, however, the metabolic mechanisms of iron(II) oxidation still remain unclear. In my PhD project, I will investigate metabolic survival strategies of iron(II)-oxidizing bacteria from freshwater ecosystems via several cultivation and molecular biological techniques, including metagenomics, metatranscriptomics, and metaproteomics. In particular, I will enrich, identify, and examine nitrate-reducing iron(II)-oxidizing bacteria to shed light on so far unresolved mechanisms of microbial iron(II) oxidation.
In my PhD project, I am investigating the impacts of dispersant and/or oil addition on hydrocarbon-degrading microbial populations in different aquatic environments. Recently, it was shown that chemical dispersants can suppress the activity of hydrocarbon degraders but the underlying mechanisms still remain unclear. Using molecular biological methods, my goal is to identify and examine hydrocarbon- and dispersant-degrading microorganisms in environmental samples and to further characterize their activity under different conditions. Podcast with Saskia Rughöft from the Microbiology Society Annual Conference: https://microbepost.org/2017/04/28/podcast-annual-conference-2017-roundup/
Despite the fact that diffuse oil sources are the main anthropogenic input of oil into the marine environment, the knowledge on microbial hydrocarbon degradation at low oil concentrations is still insufficient. Thus, during my PhD, pure cultures and environmental water microcosms will be investigated using molecular biology, GC-MS analysis and 14C-based hydrocarbon degradation assays. Furthermore, a model will be developed to predict hydrocarbon degradation, taking into account different environmental parameters. The overall aim is to gain a comprehensive understanding on the impact of small-scale pollution on different microbial communities and their hydrocarbon degradation performances by applying a combination of experimental and modelling approaches.
MSc Student - Rebecca Debo
In modern agriculture, the benefits of pesticides contribute greatly to plant health and increased food production. However, residues of many pesticides are found ubiquitously in the environment, even after they have long been phased out (e.g. atrazine). In addition to, for many pesticides such as glyphosate little is known about their environmental impact and degradation pathways. In my project I will enrich and isolate microorganisms that contribute to the turnover of atrazine and glyphosate, the most widely used herbicides globally. The isolates derive from four different sites in the catchment area of the river Ammer near Tübingen (groundwater, sediment of the Ammer spring, and agricultural soil). Furthermore, I will characterize the isolates and their degradation capabilities by use of microbial biological techniques.
Pyrite oxidation by acidophilic chemolithoautotrophic microorganisms in mining regions leads to high input of heavy metals into local rivers, such as the Rio Tinto in Spain. When acidic river water contaminated by heavy metals is mixed with pH-neutral waters geochemical changes occur, however, their impact on microbially mediated processes and the mobility of heavy metals remains unknown. I will address : i) how tides influence microbial communities, ii) how hydrogeochemical conditions and microorganisms contribute to Fe(II) oxidation and heavy metal uptake, and iii) how heavy metals are distributed between water, colloidal fraction, sediment and rock matrix.
I am currently a Marie Skłodowska Curie Fellow at the University of Tübingen, Germany and Stanford University, USA. My research focuses on biogeochemical processes in the rhizospheres of crops and phytoremediating plants when stressed with metallic soil contaminants and a shifting climate. I investigate biogeochemical changes that occur at the micrometer scale in the rhizosphere to explain macrosopic outcomes of plant productivity and quality. My goal is to contribute to advancing sustainable agriculture, which is key to the global challenge of food security. http://www.mariemuehe.com/
High level of arsenic (As) in groundwater of the densely populated Red River delta is a serious health threat for millions of people. The rural population of Hanoi region mainly depend on shallow wells which provides drinking water from Holocene aquifer. However, As concentration in these waters frequently exceeds WHO drinking water limit of 10 µg/L, in some cases reaching over 300 µg/L. Microbially mediated processes are important for As mobilization, yet these processes are still not fully understood. The main goal of my PhD project is to investigate the role of bacteria controlling As dynamics in the Fe-dominated redox transition zones, which might be crucial in As transport and retention.
The fate of critical pollutants in aquifers, obtaining recharge from agricultural landscapes, frequently depends on microorganisms that have the ability to metabolize these pollutants, such as pesticides. In my research, I will quantify the metabolic rates of pollutant turnover and determine the factors limiting these rates using biomass obtained from groundwater monitoring wells. I will also examine the potential key players responsible for pollutant turnover using microcosm experiments including stable-isotope probing in combination with gene sequencing.
- Dr. Lu Lu, postdoctoral project: "Dispersant impacts on the activity of dispersant- and/or oil-degrading microorganisms as well as phytoplankton in pristine habitats of the North Sea" (2016 - 2018)
- Katrin Wunsch, MSc thesis: " Effects of crude oil versus water-accommodated fraction (WAF) addition on marine microbial communities and hydrocarbon degrading bacteria" (2018)
- Joseph Donald Martin, MSc thesis: “Assessing the efficiency of a novel isolation technique: Microbial Trapping Devices and their influence on the bacterial community of a karst aquifer" (2018)
- Anjela Thon, MSc thesis: “Effects of surfactants on marine hydrocarbon degrading microorganisms" (2017)
- Raphael König, BSc thesis: "Atrazine and nitrate degradation in selected wells in the Ammer catchment area" (2018)
- Nelly Wang, BSc thesis: “Identification of potential crude oil or chemical dispersant degrading marine bacteria" (2017)
- Katharina Meyer, BSc thesis: “Identification of acetate-assimilating bacteria in the nitrate-reducing iron-oxidizing Culture KS using stable-isotope probing” (2016)