Research

Research focus

The scientific branch limnology deals with inland waters as ecosystems. Limnologists study the biology, physics, chemistry and ecology of rivers, lakes, groundwater and wetlands. Currently, the importance of limnology increases due to processes like climate change, pollution of surface- and ground-waters. The research focus of the Limnological Station Kilchberg starts with the smallest independent organisms, namely bacteria, but concerns also the huge variety of unicellular eukaryotic organisms (e.g. algae, protozoa). Beside bacteria, protists belong to the oldest (3 billions) and smallest (a hundredth of one millimetre) organisms. For limnologists, bacteria and protists are of great importance as they are excellent indicator organisms for the characterization of inland waters (e.g. pollution effects).

Die Limnologie ist die Wissenschaft von den Binnengewässern als Ökosysteme. Die Limnologie befasst sich also mit der Biologie und Ökologie von Fließgewässern, Grundwasser, Feuchtgebieten und Seen. Wasser wird einen noch höheren Stellenwert in unserer Gesellschaft erhalten als es jetzt schon hat. Denken Sie z.B. an Badegewässer, Verschmutzung von Gewässern, Trinkwasserqualität, Wassermangel und Überschwemmungen. Der Forschungsbereich der Limnologischen Station Kilchberg beginnt bei den kleinsten selbständigen Organismen, den Bakterien, umfasst aber auch die vielseitige Welt aller Einzeller (tierisch = Protozoa und pflanzlich = Algen). Einzellige Lebewesen (z.B. Wimpertierchen) gehören neben den Bakterien zu den ältesten (circa 3 Milliarden Jahre) und kleinsten (hundertstel Millimeter) Organismen auf der Erde. In Flüssen, Seen und Böden werden Bakterien und Einzeller zur Gütebestimmung herangezogen, da sie sich aufgrund kurzer Entwicklungszeiten (Stunden bis Tage) laufend auf Veränderungen in ihrer Umgebung einstellen können.

Cyanobacterial toxins: characterization and toxicity to aquatic organisms

Project leader:

Blom Judith, Pernthaler Jakob, Gademann Karl, Fent Karl

Investigators:

Esther Kohler, Verena Grundler, Marialuisa Pioppi

Duration:

from 2011-01-01 until 2013-12-31

Summary:

We aim at understanding the occurrence and ecotoxicological effects of selected cyanobacterial toxins and elucidating their uptake and modes of action in fish. The data will contribute to the hazard and risk assessment.
Background
Cyanobacteria have gained worldwide importance as their intense growth in eutrophic surface waters. Microcystis and Planktothrix spp. are most often observed to develop high densities in lake water. These phytoplankton species may produce harmful toxins such as cyclic oligopeptides, however, the biological functions of most cyanobacterial oligopeptides are not known. Microcystin-LR (MC-LR) may have a severe impact on aquatic biota, or even lifestock drinking contaminated water. However, in vivo uptake mechanisms and elimination kinetics of microcystins are poorly understood. Human health problems mainly originate from chronic exposure to low microcystin concentrations in poorly treated drinking water, leading to liver cancer. Cyanopeptolins, another class of cyanobacterial oligopeptides are not investigated for their toxicity. To date, there is a lack of understanding of the uptake kinetics, metabolism and effects of these peptide toxins in fish including their molecular effects.
Aims
The aim of this project is to deepen our understanding on the formation, molecular and cellular effects of these cyanobacterial toxins. Research is promoted by limnologists, environmental toxicologists and chemists focusing on a common research question, thereby investigating multiple aspects including isolation, structural and toxicological characterization, preparation of a series of derivatives to probe the toxicology and mode of action, in particular of cyanopeptolin CP1020 and MC-LR. Uptake through transmembrane transporters, kinetics and molecular and developmental effects will be studied in zebrafish. Following questions will be addressed for a better hazard and risk assessment of these toxins:

1. What toxin patterns exist in P. rubescens, and what are their chemical structures and toxicity?
2. How is the uptake, distribution and elimination kinetics of fluorescent MC-LR and CP1020 in zebrafish?
3. What is the role of uptake transporters (Oatp) and efflux transporters (ABC-transporters) in zebrafish hepatocytes?
4. What are the molecular effects and mechanisms of action of MC-LR and CP1020 on the transcriptome in zebrafish?

By tackling these questions and by linking limnology, chemistry and ecotoxicology we will provide a unique multidisciplinary training opportunity across multiple areas.

Scent of danger: Kairomone-mediated aggregate formation of a freshwater bacterium in response to protistan predation

Project leader:

Pernthaler Jakob

Investigators:

Blom Judith

Duration:

from 2009-04-01 until 2012-03-31

Summary:

The formation of microcolonies or cell aggregates by planktonic bacteria is frequently observed both in pure culture and mixed assemblages. One documented ecological advantage of such aggregates is their resistance to predation by bacterivorous flagellated protists. Some bacteria may actively respond to predation by enhanced growth of the aggregated cell type, and that such an adjustment may be due to the presence of a chemical signaling compound. We have established a model predator-prey system consisting of a bacterial isolate related to Sphingomonas sp. and the chrysomonad flagellate Poterioochromonas sp. strain DS. The Sphingomonas sp. isolate features a subpopulation of grazing-resistant aggregated cells, and significantly enhanced cell aggregation was observed after exposure to supernatants from predator-prey co-cultures. These observations point at the action of an infochemical that is potentially released during flagellate grazing and that triggers a morphological defense in the Sphingomonas sp. strain.   

 The project will study the aggregate-inducing chemical factor and the growth conditions that favor cell aggregation in the Sphingomonas sp. isolate.

(Swiss National Science Foundation - SNF)

Functional Role and Ecotype divergence in freshwater Ultramicrobacteria (FREDI)

Project leader:

Pernthaler Jakob

Investigators:

Michaela Salcher

Duration:

from 2010-07-01 until 2013-06-30

Summary:

(Funded by the Research Council of European Science Foundation (ESF), together with partners from Germany, Austria, Czech Republic)

Prokaryotic microorganisms in freshwater habitats are centrally involved in carbon turnover processes, yet individual microbial populations greatly differ in their respective metabolic and ecological features. The pelagic zone of freshwater systems is typically dominated by freely suspended ultramicrobacteria. The proposed project will study the functional differences and similarities of three monophyletic groups of freshwater ultramicrobacteria (P. necessarius, actinobacteria from the Ac1 clade and alphaproteobacteria affiliated with the LD12 lineage). It will furthermore investigate the sorting of physiologically and genotypically distinct ecotypes within each group by their specific habitats. Single-cell approaches will be combined with (meta)genomic and transcriptomic analyses both on available isolates and on uncultured ultramicrobacteria in experimental studies and comparative in situ investigations in different habitats, and the diversity and expression of functional genes (e.g., bacterial rhodopsins) will be assessed. The different levels of interactions and common activities envisaged in the proposed project will for the first time allow a synoptic view of the functional roles and phylogeographic distribution patterns of freshwater ultramicrobacteria that could not be achieved otherwise. It also offers a chance to European scientists to take a leading role in freshwater microbiology through the concerted development and application of novel functional genomic research tools.

Limnobotics: Understanding blooms of toxic freshwater cyanobacteria using an autonomous sampling platform and molecular strain typing

Project leader:

Pernthaler Jakob, Posch Thomas, Pradalier Cedric (ETHZ)

Investigators:

Garneau, Marie-Eve

Duration:

from 2010-04-01 until 2013-03-31

Summary:

(This project is a SNF-funded collaboration between the Limnological Station of the UZH, and the Autonomous Systems Lab from ETH Zurich. It will run for 3 years and will provide funding for one PhD at the ASL and one postdoc at the Limnological Station.)

The goal of this multi-disciplinary project is to provide unprecedented spatial and temporal coverage of key limnological parameters of Lake Zurich for a better understanding of the mass occurrence and population dynamics of the toxic cyanobacterium P. rubescens. We propose to develop a Autonomous Boat equipped with a variety of sensors (temperature, pH, light, oxygen, nutrients, and algal pigments) to allow for the high-frequency monitoring of cyanobacterial spatiotemporal distribution. In parallel, we will develop and apply methods to rapidly assess the contribution of toxic strains to the P. rubescens population. The boat-generated field data will serve

  1. to create a lake basin-wide model of P. rubescens development in the context of physico-chemical parameters and
  2. to guide the specific (event-driven) manual sampling campaigns and subsequent laboratory analyses, such as strain typing, gene expression of microcystin production and single-cell detection of microcystin concentration.