(i) Microbial ecology and diversity of freshwater ecosystems

(i) Microbial ecology and diversity of freshwater ecosystems.

Phosphorus and Iron Cycling: Geobiology in aquatic ecosystems

Key words

eutrophication, lake sediments, anoxia, iron-phosphate complexes, microbial iron cycle, phosphate release, sedimentation, biomass enrichment.

Description

Phosphorus retention and release is tightly coupled to iron cycling which in turn is linked to the microbially mediated cycles of sulfur and carbon. Phosphate is scavenged by ferric precipitates under oxic conditions and transported as an integral component of the iron particles. Upon reduction of the ferric matrix by ferriphilic bacteria the phosphate and ferrous iron are released. Both products can serve as nutrients for biomass formation thus driving an ecosystem production cycle. We were studying these processes in situ in the sediments of the oligotrophic Jöri lakes III and XIII. In laboratory microcosms we simulate seasonal changes under controlled conditions with the aim to disect coupled biogeochemical cycles and to understand microbial adaptation to seasonal transients. Amorphous iron-phosphate particles were detected in sediments and then produced in the laboratory. These particles are being characterized employing methods of solid state chemistry. Back in the field, we try to quantify and model the cycles for entire lakes in order to become able to understand the role of ferric-iron-covered erosion particle as nutrient scavenging enrichment agents in oligotrophic high mountain lakes.

Contacts

Kurt Hanselmann

Collaboration

Barbara Sulzberger, Federal Institute for Environmental Sciences, EAWAG, Dübendorf.
Patricia Colberg and Norbert Svoboda, University of Wyoming

Funding

Swiss National Science Foundation.

Publications

Seasonal variation of the microbially regulated buffering capacity at sediment-water interfaces in a freshwater lake. Aquatic Sciences, 61, 1999, 59-74. M. A. Lazzaretti-Ulmer and K. W. Hanselmann
Geomicrobiological coupling of sulfur and iron cycling in anoxic sediments of a meromictic lake: sulfate reduction and sulfide sources and sinks in Lake Cadagno. Documenta Ist. ital. Idrobiol. 63, 1998, 85-98. K. Hanselmann and R. Hutter.

Key words	Biogeochemical cycles, atmospheric nutrient input, oligotrophic mountain lakes, meteorological determinants, lake dynamics, lake heat budget, lake ice formation and melting, erosion minerals, surface chemistry, microbial communities, microbial loops.
Description	Aquatic ecosystems of high mountain environments are normally oligotrophic. They support characteristic microbial communities which have been naturally selected for the harsh conditions which exist here during most of the year. Environmental changes, meteorological and chemical ones, are reflected rapidly in these habitats. Even small alterations in the water constituents can be detected with the aid of modern analytical methods and changes in the composition of the microbial community (population diversity) as well as its physiological behavior respresent biological signals indicative for environmental changes. The major questions to be answered are: How do climatic changes and atmospheric precipitation composition affect the food web in high mountain aquatic ecosystems ? By what mechanism does the nutrient input affect the available nutrient regime in presence of high numbers of chemically reactive surfaces from the catchment erosion minerals ? How rapidly can oligotrophic ecosystems adapt to man-made environmental changes, i.e. to enlarged nutrient loads, to acidification and to pollutant imissions or even to several of these factors when they influence mountain ecosystems simultaneously ?
Contacts	Matthias Gabathuler, Philipp Roelli, Hans - Rudolf Preisig, Kurt Hanselmann
Collaboration	Donat Högl and Albert Waldvogel, Laboratory for Atmospheric Physics of the Swiss Federal Institute of Technology;Hans-Rudolf Preisig, Institute of Systematic Botany, University of Zürich; Ferdinand Schanz, Limnology Dept. University of Zürich; Olivier Besson, Dept. of Mathematics, University of Neuchâtel; Armand Vernez, Swiss Meteorological Service, Payerne; Urs Krähenbühl, Institute of Inorganic Chemistry and Biochemistry, University of Bern;
Funding	Swiss National Science Foundation and Swiss Federal Office for Education and Research.
Publications	Seasonal dynamics and phytoplankton diversity in high mountain lakes (Jöri lakes, Swiss Alps). J. Limnol.,58/2, 152-161, 1999. Hinder, B. , M. Gabathuler, B. Steiner, K.W. Hanselmann, H.R. Preisig. Microbial food web in an oligotrophic high mountain lake (Jöri lake III, Switzerland). J. Limnol.,58/2, 162-168, 1999. Hinder, B., I. Baur, K.W. Hanselmann, F. Schanz.

(ii) Environmental Regulation of Toxin Production by Cyanobacteria in cold-extreme Mountain Habitats

Key words	cyanobacteria, toxin, microcystins, benthic biofilms, psychrophile, high mountain environments, cold adaptation, molecular techniques.
Description	Cyanotoxins are metabolites with inhibitory, toxic or even lethal effects on other organisms. They are produced by planktic and benthic cyanobacteria. Developments of cyanobacteria under the harsh and extremely variable conditions of high mountain environments are often limited to benthic mats. The synthesis of the harmful metabolites may be induced by resource imbalances. Our research addresses questions related to the detection of cyanobacteria from cold-extreme environments, the determination of their toxicity and the analysis of the role of their toxins. We would like to apply the research results to predict whether, under which conditions and when a particular cyanobacterial population begins to proliferate into a hazardous biofilm development and what factors will induce toxin production. We like to know more about the factors which regulate the synthesis of toxic metabolites and to develop diagnostic tools which allow to make reliable predictions about the regulation of toxin production. Our model organisms are oligotrophic cyanobacteria from thin bacterial mats present in high mountain aquatic ecosystems (lakes, ponds, swamps). We are interested to find out: (i) how the different species present in these biofilms get selected by environmental determinants and whether the ”toxins” they produce are molecules of communication or ”weapons” which help certain species to ”fight” for dominance; and (ii) we are trying to find the promotor region for the enzyme microcystin synthetase in order to experimentally confirm regulation of toxin production by environmental factors. We would also like to be able to design specific molecular probes to learn more about the distribution of toxin-producing genes (Microcystin synthetases) in cyanobacterial species present in these cold-extreme, oligotrophic environments.
Contacts	Munti Yuhana, Kurt Hanselmann
Collaboration	H.- R. Preisig, Institute of Systematic Botany, University of Zürich
Funding	Department of Defence.
Publications	Environmental conditions in high mountain lakes containing toxic benthic cyanobacteria. Hydrobiologia, 368, 1998, 1-15. K. Mez, K. Hanselmann and H.R. Preisig. Plötzliche Todesfälle von Alprindern im Kanton Graubünden. Schweizer Archiv für Tierheilkunde 139, 1997, 201-209. H.Naegeli, A.Sahin, U.Braun, B.Hauser, K.Mez, K.Hanselmann, H. R.Preisig, A.Bivetti, J.Eitel Identification of a microcystin in benthic cyanobacteria linked to cattle deaths on alpine pastures in Switzerland. Eur.J.Phycol. 32, 1997, 111-117. K.Mez, K.A.Beattie, G.A.Codd, K.Hanselmann, B.Hauser, HP.Naegeli, H.R.Preisig.

Key words	biofilm classification, microbial communities, corrosion diagnosis, molecular techniques, PCR, RFLP, ARDRA, RCCH, surface growth, electron acceptor, depolarization.
Description	In collaboration with various European firms and government agencies, we are in the process of developing a series of well defined, reproducible, standardized, validated, cost-effective and easy to perform assays for the characterization of biofilm organims on production materials and a key to their corrosion potential. In collaboration with corrosion and material testing laboratories we attempt to microbiologically classify corrosive and non-corrosive biofilm types by characterizing the community composition and its changes during biofilm development and relate composition to corrosive activities. We apply molecular techniques for the identification of bacteria as part of our contribution to a European industrial corrosion-research project. This research project is a first attempt to classify microbial biofilm types by characterizing their organismic composition and their activities as well as to reconstitute biofilms with predictable surface alteration capabilities.
Contacts	Christine Lehmann, Marcello Marchiani, Kurt Hanselmann
Collaboration	Sulzer Innotec AG, Winterthur, Switzerland, Department of Chemistry, University of Wales, Bangor, U.K., National Research Institute for Radiobiology and Radiohygiene, Dept. of Radiobiology, Budapest, Hungary. EMPA (Swiss Federal Institute for Materials Testing), Biology Dept., St.Gallen, Switzerland, and Universidad Politécnica de Madrid, Departamento de Ingenieria y Ciencia de los Materiales, Escuela Tècnica Superior de Ingenieros Industriales.
Funding	COST 520 (cooperation europeenne dans le domaine de la recherche scientifique et technique); through the Swiss Department for Research and Education.

Key words	GEM, protozoa, gene transfer, slide method, DNA stability, biosafety.
Description	As a contribution to the public discussion about biosafety concerns of gene technology we were studying gene transfer in high density bacterial conglomerates, i.e. in biofilms grown on a variety of materials and in vacuoles of protozoa which are the first link in food webs of aquatic and soil ecosystems. This project connects to fundamental questions about microbial evolution by horizontal gene transfer under natural conditions. It was the aim of the study to evaluate the role of genetically altered bacteria as vectors for genes in aquatic ecosystems and to better understand the ecophysiological fate of GEMs (genetically engineered microorganisms) in natural microbial habitats. As a test system we use trophic interactions between microorganisms in the aquatic food chain. We monitored the behavior of the predator towards various bacterial diets (GEMs and wild type bacteria) and developed test methods based on structural changes and the physiological behavior of the protozoan predators. We found that certain bacteria survive the digestion process in the food vacuole and are thereby enriched in the environment. Other bacteria invade the predator's cytoplasm and kill it, and some bacteria kill their predators through toxic metabolites or virulence factors. Conjugation and transformation can take place between engulfed bacteria which makes digestive vacuoles of protozoa microniches that promote horizontal gene transfer. We developed a slide technique which allows for the detection of single fluorescent transformants. Based on this technique we developed a test for the evaluation of bacterial toxicity towards protozoa of the food web. We recommend and are marketing the assay for biosafety evaluations. Employing the slide technique we discovered that genetic transformation of bacteria is much more frequent if detected under non selective conditions and that even heat-treated DNA can still be transcribed in recipient transformants. This implies that gene transfer is probably much more common in nature than it has been assumed so far.
Contacts	Marcello Marchiani, Bernard Jenni (Novartis), Kurt Hanselmann
Cooperation	Biosafety Department of Novartis, AG.
Funding	Swiss National Science Foundation and Novartis, AG, Basel.
Publications	BACTOX: A rapid bioassay using protozoa to assess the toxicity of bacteria. Appl. Environ. Microbiol. 65, 1999, 2754-2757. Schlimme, W., M. Marchiani, K. Hanselmann and B. Jenni. Gene transfer between bacteria within digestive vacuoles of protozoa. FEMS Microbiology Ecology 23, 239-247, 1997. Schlimme, W., M.Marchiani, K.Hanselmann, B.Jenni. Genetic transformation in freshwater: Escherichia coli is able to develop natural competence. Applied and Environmental Microbiology 62, 3673-3678, 1996. Baur, B., K.Hanselmann, W.Schlimme, B.Jenni.

Key words	eutrophication, lake sediments, anoxia, iron-phosphate complexes, microbial iron cycle, phosphate release, sedimentation, biomass enrichment.
Description	Phosphorus retention and release is tightly coupled to iron cycling which in turn is linked to the microbially mediated cycles of sulfur and carbon. Phosphate is scavenged by ferric precipitates under oxic conditions and transported as an integral component of the iron particles. Upon reduction of the ferric matrix by ferriphilic bacteria the phosphate and ferrous iron are released. Both products can serve as nutrients for biomass formation thus driving an ecosystem production cycle. We were studying these processes in situ in the sediments of the oligotrophic Jöri lakes III and XIII. In laboratory microcosms we simulate seasonal changes under controlled conditions with the aim to disect coupled biogeochemical cycles and to understand microbial adaptation to seasonal transients. Amorphous iron-phosphate particles were detected in sediments and then produced in the laboratory. These particles are being characterized employing methods of solid state chemistry. Back in the field, we try to quantify and model the cycles for entire lakes in order to become able to understand the role of ferric-iron-covered erosion particle as nutrient scavenging enrichment agents in oligotrophic high mountain lakes.
Contacts	Kurt Hanselmann
Collaboration	Barbara Sulzberger, Federal Institute for Environmental Sciences, EAWAG, Dübendorf. Patricia Colberg and Norbert Svoboda, University of Wyoming
Funding	Swiss National Science Foundation.
Publications	Seasonal variation of the microbially regulated buffering capacity at sediment-water interfaces in a freshwater lake. Aquatic Sciences, 61, 1999, 59-74. M. A. Lazzaretti-Ulmer and K. W. Hanselmann Geomicrobiological coupling of sulfur and iron cycling in anoxic sediments of a meromictic lake: sulfate reduction and sulfide sources and sinks in Lake Cadagno. Documenta Ist. ital. Idrobiol. 63, 1998, 85-98. K. Hanselmann and R. Hutter.