Research activity

The Alpine Biology Centre of Piora (CBA) aims to promote university teaching, scientific research and the dissemination of research results in the Val Piora region. The Institute of Microbiology of SUPSI (IM-SUPSI) provides scientific support to the CBA for activities mainly related to environmental microbiology.

Scientific research at Piora, coordinated by IM-SUPSI in collaboration with the Universities of Geneva and Zurich, is funded by the Swiss National Science Foundation (SNSF) for research.

The SNSF is currently funding a project whose main objective is to study the effects of the bioconvection process on the ecophysiology of the main microbial species in the chemocline (BIOCAD 2018-22).

Other Swiss and world universities are also attracted to research in the Val Piora area, both in limnology and in other fields such as botany and geology.

Microbial and molecular ecology of microorganisms in stratified water systems

Knowledge of the various organisms in Lake Cadagno is linked to the biogeochemical cycles of the most important compounds, especially sulphur, to energy flows and metabolic transformations; this allows a global approach to the network of processes present in complex aquatic systems.

The dolomite vein (Sacca di Piora or Pioramulde) of Val Piora, which has been mentioned in the media because of possible problems related to the construction of the Alptransit tunnel, enriches part of the waters of Val Piora with mineral salts (carbonates, magnesium, sulphates, etc.). These waters come from underwater springs and are stratified at the bottom of Lake Cadagno. This results in a permanent stratification, or meromixis, of the water mass with the formation of two layers, a superficial layer (from 0 m to 12 m depth) composed of water poor in salt and oxygen, superimposed on an anoxic layer (from 12 m to a maximum depth of 21 m). A transition zone between oxic and anoxic water, commonly called chemocline, is present at about 12 m; here the ideal conditions are found (light, absence of oxygen, presence of sulphides) for the massive development of a community of phototrophic anaerobic sulphuric bacteria linked to the sulphur cycle, which represent an additional primary production, in addition to that of the algae in the surface layer. It is precisely because of the photosynthetic activity of these chemocline bacteria that Cadagno can support many more fish than an ordinary alpine pond, making it very popular with fishermen.

This transition zone also shows a relatively stable vertical stratification of bacterial populations adapted to different depths (e.g. sulphur phototrophic bacteria, chemoorganotrophic bacteria, methane and sulphide oxidising bacteria, sulphate and nitrate reducing bacteria, iron and manganese oxidising bacteria, methanogens, etc.). This natural phenomenon, known as crenogenic meromixis, is of particular interest as it offers the possibility of following the processes of biomass production and mineralisation in the natural state. The great advantage offered by Lake Cadagno is that the stratification of the reactions and bacterial populations mentioned is present over a thickness of about 2 metres, which means that they can be easily sampled. In lakes without this water stratification phenomenon, these processes usually take place between the water mass and the sediments over a space of a few centimetres, and therefore with greater methodological difficulties of investigation.

Crenogenic meromixis in Lake Cadagno is a unique phenomenon in the Alps and rare worldwide. Its importance lies in the fact that it represents a natural habitat of high microbial biodiversity that serves as an ideal model for understanding the role of microorganisms in global biogeochemical cycles. The concept of environmental biodiversity at the level of microscopic organisms is generally poorly understood, but is gaining in importance with the development of specific molecular methodologies that allow targeted, precise and highly accurate analyses.

The main objective of the microbial ecology studies at LMA-SUPSI is the analysis and characterisation of the composition, spatial and temporal distribution of key species as well as the study of the diversity of the main microbial populations and their physiological activity in the different compartments of the lake.

Ongoing projects

Microbial Ecology Laboratory Uni-Ge/IM-SUPSI

Bioconvection-mediated microbial ecophysiology in aquatic systems - Multi-scale dynamics in the chemocline of meromictic Lake Cadagno

Lake Cadagno shows a permanent stratification of the water throughout the year, with the upper oxygen-containing water layer above an anoxic layer rich in dissolved salts. Red sulphur anaerobic bacteria (RSA) of the species Chromatium okenii thrive at the interface of the two layers, where they are able to mix considerable volumes of water, not by stirring it directly with their flagella, but by clustering together in search of light in a restricted area near the oxygen diffusion front. In doing so, the volume density increases and the water begins to fall, taking the micro-organisms with it in a process known as bioconvection.

The main objective of this project (PhD Francesco Di Nezio UNIGE and PostDoc Nicola Storelli SUPSI) is to study the effects of the bioconvection process on the ecophysiology of key microbial species in aquatic environments. Through a multidisciplinary approach, the chemical and physical environmental conditions necessary for the optimal development of microorganisms will first be determined. Subsequently, the eco-physiological effects of bioconvection will be studied by setting up microcosms in the laboratory and by carrying out analyses directly in the lake (thanks to the facilities of the Centre for Alpine Biology in Piora). At the end of this project, we will finally be able to lay the foundations for understanding the consequences of bioconvection on the whole lake ecosystem.

It is assumed that the anaerobic phototrophic sulphur bacteria studied in this project are part of the first life forms that appeared on Earth, when oxygen was not yet present. These primitive micro-organisms could therefore represent the starting point of the whole evolutionary process that led to a massive and heterogeneous presence of life on our planet. The comparison and interaction of different species of phototrophic sulphobacteria that are ecologically very similar, but physiologically very different, will reveal important details about three distinct evolutionary lineages of the three main bacterial populations in the lake.

CO2 and H2S assimilation rates of the most important phototrophic sulphur bacteria of the Lake Cadagno chemocline

The aim of this project (master Clarisse Beney UNIGE) is to analyse the different rates of sulphide (H2S) oxidation and the efficiency of carbon dioxide (CO2) assimilation for the most important populations of anaerobic phototrophic sulphur bacteria living in the chemocline of Cadagno Lake, namely the red bacteria (PSB) Chromatium okenii LaCa, "Thiodictyon syntrophicum" Cad16T and the green bacteria (GSB) Chlorobium pheobacteroides.

The oxidation rate and affinity will be measured for each of the three micro-organisms at different light intensities and starting H2S concentrations. For these measurements, a microbreathing device capable of measuring the smallest fluctuation of H2S in real time (SULF UNISENSE sensor) will be used. In addition, it will also be interesting to evaluate other electron donors such as thiosulphate (S2O32-), as well as the use of intracellularly stored S0 for PSB or externally excreted S0 for GSB.

The effective capacity and rate of CO2 fixation will be evaluated for the three microorganisms under different laboratory conditions, including microaerophilic conditions (<5% O2) and continuous darkness, and during the summer directly in the lake using dialysis bags. The study will also be completed by a transcriptomic analysis, mainly to compare the metabolism in the presence of light with that in the dark. This analysis should finally reveal the metabolic processes that allow good CO2 fixation activity in the absence of light.

Population dynamics

Over the last 25 years, increasingly efficient bacterial identification techniques have been developed and applied, and then validated and standardised so that they are available as a service at LMA-SUPSI (identification and typing of environmental micro-organisms). The dynamics of bacterial populations, in particular phototrophs, is fundamental for the structure and ecological activity of the lake. In order to monitor the microbial population dynamics of Lake Cadagno, a complete monitoring is planned every year (LMA researchers Samuele Roman and Nicola Storelli) at the beginning, middle and end of the season for chemical values using the MERCK spectroqunt kit, physical values using the CTD Sea and Sun multiparameter probe and biological values using fluorescence in situ hybridization (FISH) and flow cytometry.

Completed projects

Functional genomics of purple sulphur bacteria from Lake Cadagno

Samuel Lüdin's PhD project (2018 UNIGE) was mainly focused on the genomics and proteomics of the main anaerobic phototrophic sulphur bacteria of Lake Cadagno. During his thesis, Lüdin succeeded in completing the chromosomal and plasmid sequence of 2 very important species for the ecology of the lake such as the PSB strain Cad16T "Thiodictyon syntrophicum" and the PSB strain LaCa Chromatium okenii. The genetic knowledge of the anaerobic phototrophic sulphur bacteria community opens the door to future, more detailed metaproteomic (or metatranscriptomic) analyses with the aim of increasing knowledge of the ecological importance of this particular type of microorganism. One of the main characteristics of this species is its great capacity to fix CO2 not only in the presence of light, but also in the dark. For this reason, although the Cad16T strain of "T. syntrophicum" represents only about 2% of the total community of phototrophic anaerobic sulphur bacteria, it contributes to almost 25% of the total primary production of Lake Cadagno. Further studies on the metabolism of the PSB Cad16T strain "T. syntrophicum" have revealed factors differentially expressed under light and dark conditions, which can now be better interpreted thanks to complete genomic knowledge. Furthermore, this research lays the foundation for the development of targeted laboratory and in situ experiments aimed at understanding the role of these important microorganisms in the Cadagno Lake ecosystem. The project was carried out in collaboration with the Spiez Laboratory (Dr. M. Wittwer), the Zurich-Wädenswil University of Applied Sciences ZHAW (Dr. J. Pothier), the company Mabritec (Dr. V. Pflüger) and the University of Geneva (Prof. M. Goldschmidt-Clermont and Prof. M. Hothorn).

Flow cytometry as a tool to investigate the coexistence of phototrophic anoxygenic sulphur bacteria in the chemocline of the meromictic lake Cadagno.

Francesco Danza's PhD work (2018 UNIGE) focused on the use of flow cytometry for the rapid recognition and counting of anaerobic phototrophic sulphur bacteria in Lake Cadagno. Furthermore, due to the change in cell complexity related to the accumulation of sulphur globules (S0) during anaerobic photosynthesis, it was possible to apply flow cytometry to also assess the metabolic activity of each individual cell. By means of flow cytometry, an attempt was made to understand some of the behaviour of the populations, both at the global and individual level. The idea was to transfer the model obtained with the laboratory data to the more complex system of the natural environment in which these micro-organisms live in the presence of other species. The efficiency and precision of flow cytometry also made it possible to establish a correlation between turbulence, measured by Professor Johny Wuest's research group at EPFL, and the motive activity of the Chromatium okenii species. The measurements carried out directly in Lake Cadagno, applied to mathematical simulations, led to a scientific publication in the journal "Geophysics Research Letters", showing and validating for the first time a "bioconvection" process in nature (previously, the phenomenon had only been observed in the laboratory). This work is part of a collaboration between the "Surface Water" group at EAWAG, the "Microfluidics" group at ETHZ and the "Biogeochemistry" group at the Max Planck Institute in Bremen.

(https://archive-ouverte.unige.ch/unige:103201)

Role of phototrophic sulphur bacteria of the chemocline in the primary production of Lake Cadagno

Nicola Storelli's PhD work (2014 UNIGE) showed the importance of anaerobic phototrophic sulphur bacteria in the primary production of Lake Cadagno. Indeed, these bacteria contribute significantly to the total primary production of the lake with high values of carbon dioxide (CO2) fixation in the presence of light (photosynthesis) and especially in the dark with a still unknown mechanism. The red sulphur bacterium PSB Candidatus "Thiodictyon syntrophicum" strain Cad16T was found to be the best CO2 assimilator among the various dominated populations (excluding PSB Chromatium okenii)

in the Lake Cadagno chemokine and was therefore used as a model organism to try to understand dark fixation. Analysis of the different proteomes (light and dark) by 2D difference gel electrophoresis (DIGE) showed the presence of 23 proteins more present in the light and 17 in the dark. Of the 23 proteins more present in the light, three were involved in the production of intracellular storage globules (poly-3-hydroxybutyrate) that store reducing power (NAD(P)H) and carbon compounds (acetyl-CoA). In the dark, of the 17 most abundant proteins, three were part of the autotrophic cycle found only in the archaeal kingdom, the "dicarboxylate-hydroxybutyrate" (DC/HB). However, this DC/HB cycle is nothing more than the sum of the more common reverse tricarboxylic acid (rTCA) and beta-oxidation cycles, especially the latter responsible for the utilisation of storage globules produced in the presence of light (poly-3-hydroxybutyrate).

In addition, the raw genome sequences (contigs) sequenced for the first time from strain Cad16T revealed the presence of two RuBisCO genes (cbbLS and cbbM), crucial for CO2 fixation by the Calvin cycle, which are differentially expressed. RuBisCO type II cbbM is constitutively expressed (unregulated) while the more evolved RuBisCO type I cbbLS is regulated by its environment.

(https://archive-ouverte.unige.ch/unige:34915)

Cantonal Institute of Microbiology (ICM)

Syntrophic aggregates of Thiodictyon syntrophicum CAD16 and Desulfocapsa thiozymogenes CAD626 from Lake Cadagno

Lake Cadagno and permanently stratified lakes in general are ideal models for the study of aquatic microorganisms. Lake Cadagno is particularly interesting for the presence of populations of photo-synthetic sulphur bacteria and sulphate-reducing bacteria. In recent years, it has been shown that photosynthetic red sulphur bacteria belonging to the candidate species Thiodictyon syntropicum Cad16 and sulphate-reducing bacteria of the species Desulfocapsa thiozymogenes Cad626 are able to associate in structures called aggregates. Until now, a detailed study of how aggregation could take place was not feasible due to the impossibility of reproducing the structure of aggregates in the laboratory. With this master thesis directed by Nicholas Vecchietti (2011 UNI Insubria), for the first time, we succeeded in identifying the ideal conditions that allow the reproduction of the bacterial aggregate in the laboratory.

Paleo-microbiology of Cadagno Lake sediments

In 2009, an interdisciplinary research project on the anoxic sediments of Lake Cadagno was conducted in collaboration with ETH Zurich, the University of Basel and NordCEE Denmark. This research allows the study of landslides and is combined with the evolutionary history of microbial populations that occurred in the lake.

In particular, a post-doctoral research project (Damiana Ravasi) focused on the extraction of subfossil DNA from samples from different depths of the anoxic sediment. Quantification of subfossil ribosomal RNA sequences of different populations of sulphuric phototrophic bacteria revealed their presence throughout the sediment. The bacterial populations show variations in concentration depending on the depth at which they were found, indicating significant changes in the biological history of the lake. The dating of the 10-metre sediment core, which corresponds to the biological history of 10,000 years, is in progress.

Molecular approach to the study of sulphate-reducing bacteria and methanogenic Archaea in the sediments of lakes Cadagno and Rotsee.

The aim of Michel Bottinelli's thesis (UNIGE 2008) was to compare the final stages of microbial mineralisation, by examining methanogenesis and sulphate reduction, in the deep sediments of two lakes with different sulphate concentrations (Lake Cadagno and Lake Rotsee). In Lake Cadagno, sulphate reduction dominates ([SO₄²-] = ~ 3 mM; [S²-] = 2-3 mM), whereas Lake Rotsee shows a predominance of methanogenesis ([CH₄] = 5 mM; [SO₄²-] = ~ 1 μM). At the water-sediment interface, TOC and THAA values were twice as high in Cadagno (149 and 77 mg g-¹ of sediment). The 16S rDNA analysis showed a prevalence of bacteria with an average of 59% and 15%, including 55% and 10% of sulphate-reducing bacteria (SRB) as well as the kingdom "Archaea" with 27% and 4% in the DGGE profiles of Lake Cadagno and Rotsee respectively. In addition, the sediments of Lake Cadagno showed a higher diversity of bacterial 16S rDNA at different sediment levels.

(https://archive-ouverte.unige.ch/unige:98209)

Proliferation of new phototrophic sulphur bacteria in the chemocline of the meromictic Lake Cadagno: what consequences?

Following an extraordinary water mixing event in October 2000, a change in the populations of green phototrophic sulphobacteria (GSB) was observed, from Chlorobium phaeobacteriodes to Chlorobium clathratiforme. An increase in the abundance of GSBs compared to total phototrophic sulphobacteria was also observed: from 5-10% between 1994 and 1999 to 95% in 2002.

The aim of the "Diplôme d'études approfondies (DEA)" study conducted by Paola Decristophoris (2007 UNIGE) was to highlight the distribution in the chemocline of green phototrophic sulphobacteria (GSB) and violet sulphobacteria (PSB), two families with very similar metabolic requirements, and to understand whether changes in relative abundance between the two taxonomic groups had an effect on the vertical distribution of PSB populations.

The total biomass of phototrophic sulphobacteria increased threefold between 1998 and 2004. This increase was directly related to the proliferation of GSBs, while the biomass of PSBs remained unchanged. It would also appear that this had no impact on the microstratification of GSBs at different depths in the water column. The proliferation of GSBs suggests the appearance of an ecological niche in the Lake Cadagno chemocline after 1999, which C. clathratiforme was able to colonise without any measurable impact on the other phototrophic sulphobacteria already present.

Interactions between sulphate-reducing bacteria and purple sulphur bacteria in the chemocline of the meromictic lake Cadagno

Our attention, while maintaining the phylogenetic aspects, had shifted more towards the analysis of physiological activities, interactions with the external environment (lake water) and between organisms (syntropy and symbiosis). Indeed, Sandro Peduzzi's doctoral work (2003 ETHZ), in collaboration with Rutgers University in Newark, USA (D. Hahn) and EAWAG (ETH) in Dúbendorf (A. Zehnder), focused on the formation of a bacterial aggregate in Lake Cadagno. In the chemocline (11-14 m) of Lake Cadagno, part of the microbial community develops into a structure called an aggregate; this is composed of two bacterial species: red sulphur bacteria (RSB) of the family Chromatiaceae (Thiodictyon sp.) and sulphate-reducing bacteria (SRB) of the family Desulfovibrionaceae (Desulfocapsa thiozymogenes). The tight aggregation association is species-specific but not obligatory and is beneficial for the survival of both species involved. The project focused on identifying the chemical and physical conditions that induce the formation of the aggregate and understanding its structure (three-dimensional studies by confocal microscopy) in order to clarify its eco-physiological role.

Isolation of anaerobic bacteria from Lake Cadagno (late 1990s)

With the isolation and anaerobic culture techniques for phototrophic (e.g. Lamprocystis) and sulphate-reducing (e.g. Desulfocapsa) bacteria, the way has been opened for laboratory physiological studies combined with molecular methods. The cultivation and study of the metabolic activities of these micro-organisms correlate with the activities of their habitat and open the way to interesting biotechnological developments, such as the cultivation of phototrophic bacteria capable of purifying water from harmful substances such as sulphides and ammonia or the cultivation of bacteria capable of degrading pollutants that are difficult to remove from the environment, such as pesticides, and in particular organohalogens (genus Desulfomonile).

Characterisation of anaerobic bacteria in Lake Cadagno

The introduction of direct or "in situ" analysis methods with the fluorescence microscope was decided after the first works in the 1980s, based on the classical methods of environmental microbiology, given the low percentage of cultivable bacteria (<0.1%) in the samples taken from the lake compared to the bacteria actually present. Thanks to the collaboration with the CNR-Istituto di Ricerca per gli Ecosistemi of Pallanza, the counts of cultivable bacteria were complemented by direct counts of total bacteria after nucleic acid staining. Thanks to these methods, it was possible to discover and enumerate separately particular and abundant bacterial morphotypes in the different layers of the lake (diploma work J.-C Bensadoun 1995). The acquisition of the "Whole Cell Hybridization (WCH)" technique in collaboration with the Institute of Terrestrial Ecology of ETH Zurich (D. Hahn) and the Technical University of Munich and the Max Planck Institute of Bremen (R. Amann) initiated the introduction of "in situ" molecular detection methods applied to the Lake Cadagno samples. The first counts after cell hybridisation were carried out in 1994.

In 1995, the introduction of automated nucleic acid amplification (PCR) and sequencing made it possible to start the first work on the amplification and cloning of genes coding for 16S ribosomal RNAs, thus opening up wide possibilities for the typing of non-cultivable strains and the analysis of environmental microbial populations. This work allowed the development of specific detection techniques for bacteria present in Lake Cadagno in order to describe their spatio-temporal distribution. This has led to the discovery of previously undescribed species of phototrophic and sulphur-reducing bacteria that are present in the transition zone between the oxic and anoxic layers of the lake.

Start of research activities

Considering that training activities must always be supported by continuous and updated research, the ICM decided in 1992 to resume and encourage research aimed at understanding the microbiology of Lake Cadagno, even outside the training courses. In addition to the classical methods, which are important for comparison with previous data and with other ecosystems, new techniques have been developed on molecular and biophysical bases, in particular the molecular techniques of in situ detection, which allow for greater specificity and high resolution in space and time.

At the boundary between oxic and anoxic conditions, the chemocline and moving between 10 and 13 m, the phototrophic sulfur bacteria find ideal conditions for growth: sufficient light, no oxygen but sulfide. These bacterial communities drive part of the sulfur cycle and boost the primary production in the lake. The chemocline stabilizes the stratification of the water and offers ideal growth conditions for phototrophic and chemoorganotrophic organisms.

This natural phenomenon of two rugged water layers is called krenogenic meromixis. In such a system the processes of biomass production and their mineralization take place in two different compartments. They can be studied in the lake independently. In the transition zone of up to 2 m width steep gradients of light, oxygen and sulfide are formed. The different bacterial populations with their activities are stacked; thus it became possible to sample the zone with high spatial resolution. In most other lakes we find the transition zone at the sediment surface and usually of only few mm in size which makes in situ experiments much more difficult.

The amount of bacteria from environmental samples which can be cultivated in the lab is around 0.1%, thus fluorescence microscopy substituted classical enumeration already in the 1980ies. In cooperation with the Institute for Aquatic Ecosystems at Pallanza the bacteria were quantified and characterized according to morphotypes after staining of the nucleic acids (Dissertation Bensadoun). In 1994 in situ hybridization of whole cells was started in cooperation with the Institute for Terrestric Ecology of the ETH Zürich (D. Hahn) and the Technical University in Münich and the Max-Planck-Institute at Bremen (R. Amann).

From 1995 on molecular methods such as nucleic acid amplification (PCR) and sequencing of selected gene fragments (16S ribosomal DNA) allowed to characterize non cultivable bacteria. This facilitated to describe the microorganisms in Lake Cadagno in space and time. With specifically developed DNA probes new species of phototrophic and sulfate reducing bacteria were found in the oxic-anoxic transition zone. Temperature-gradient-.gel-electrophoresis (TGGE) and denaturing-gradient-gel-electrophoresis (DGGE) expanded the knowledge on the bacterial distribution in the different layers of the lake (Dissertations Bottinelli und Shahn).

The expert knowledge in microbial ecology gained in the studies on Lake Cadagno opened the way for similar work in other ecosystems, such as the limnologic description of Lake Muzzano combined with the isolation of the bloom forming cyanobacterium Microcystis wesenbergii and the characterization of the gene responsible for the synthesis of the toxin mycrocystin (Thesis at the University of Pavia).

In a PhD thesis at the University of Geneva the ecological and genetic impacts of the biological control of the undesirable mosquito Aedes vexans by the bacterium Bacillus thuringiensis sv. israelensis was studied in cooperation with the foundation of Bolle di Magadino and financed by the Federal Office for Environment, Forest and Landscape and the Canton Ticino.

Ecological projects of the University of Zürich (Institutes for Plant Biology, Systematic Botany, and Evolutionary Biology and Environmental Studies).

Field work in the Piora Valley started in 1983 with student courses by Kurt Hanselmann. At that time the scientific and the living infrastructures in the upper floor of the barn (building C) were marginal, sleeping on pallets, a latrine and running water at the fountain on the fore court. The cooperation „Zurich-Ticino“ in ecological field work started with two students from the Ticino, Claudio Del Don and Mauro Tonolla. Claudio created in his diploma thesis the first limnologic description of the lake (1986) and Mauro studied the vertical movements of the phototrophic bacteria in the transition layer (1987). This work formed the basis of many other investigations on the chemistry and biology of the lake and of the challenging analysis of the movements of the bacterial biomass in situ. It was further studied in the diploma thesis of Johanna Loch (1989) and of René Israng (1992) using electronic sensors and finalized in the diploma thesis of Konrad Egli (1997). Konstanze Mez (1992) and Barbara Känel (1992) enlarged in a collective thesis, unique for our University, the physiologic basis of the sulfur cycle. Franziska Gassmann (1988), Michaela Waldburger-Schlapp (1990) and Adriano Joss (1993) studied the fluorescence properties of the phototrophic bacterial community from the transition layer in the lab and in situ using a home made detection system. Markus Fritz (PhD thesis 1999) expanded the lake chemistry with analyses of volatile organic sulphur compounds. Lucas Lüthy (1999) succeeded for the first time to measure in situ the rates of oxidation and reduction of the essential compounds in the sulfur cycle within the bacterial layer in the transition zone.

Microbial processes in the sediments of Lake Cadagno were first studied by Helmut Brandl (1984) and Patrick Höhener (1986), and René Hutter (1989) explained the relations between the sulfur cycle and the iron cycle in the sediments. Christine Lehmann (PhD thesis 1999) used new approaches to quantify the reduction of sulphate in the sediments and Linda Birch (PhD thesis 1993) traced the input of pollutants from the atmosphere into the remote alpine lake by studying profiles of heavy metals in sediment cores.

Yvonne Weggler (1981) searched for different sulfureta ecosystems in Switzerland and came up with the bacterial mats in the wetlands of Cadagno (Bolle di fuori). Maja Ulmer Lazzaretti (1988) characterized these mats while Markus Wiggli (PhD thesis 1997) enlarged these studies by spectroscopic measurements. Barbara Rutishauser (1997) analyzed the reductive formation of phosphine in the wetlands and Thomas Horath (1998) isolated and characterized members of the phototrophic population in the bacterial mats. Astrid Schenk succeeded fort he first time to demonstrate bacterial signal compounds (homoserine lactones) in natural bacterial communities in the mats West of Cadagno (1998).

Guided by Ferdinand Schanz the diploma students Carmen Fischer-Romero (1989), Claudia Friedl (1987), Piero Pasini (1999) and Susanne Stalder (1990) investigated the photosynthetic production of the phototrophic bacterial layer and its specific light clima ithe lake.

Rolf Stettler, trained at the ETH, introduced the molecular techniques to analyze microbial ecosystems into the group; the diploma theses of Yves Santini (1998), Dominique Grüter (1999) and the PhD thesis of Philipp Bosshard (2000) illustrate well the microbial diversity in the different layers of Lake Cadagno.

Besides the work discussed on aquatic research, some studies covered terrestrial ecosystems. The PhD theses of Andreas Schürmann (1999) and of Joachim Mohn (1999) on the liberation of nitrous oxide from alpine soils gave evidence that soil releases much more N₂O when covered with snow in winter than in summer. The PhD thesis of Thomas Horath (2010) illustrates a so far less regarded extreme ecosystem using physiological and molecular tools the endolithic microbes in the Dolomite in the Piora Valley.

A few diploma theses were accomplished at the Institute for Systematic Botany of the University of Zürich guided by Jakob Schneller on the topics biodiversity, population and reproduction biology of Polygonum viviparum (Martin Bauert, 1991), Anthyllis vulneraria (Karoline Haessig, 1993), Pulsatilla apiifolia (Evelyn Pelascini, 1993) und Euphrasia minima (Waldburga Liebst, 1999), furthermore the PhD theses von Martin Bauert (1994), Waldburga Liebst (2006) and Urs Landergott (2007).  In the group of Edwin Urmi the students Silvia Stofer (1995) and Ariel Bergamini (1995) completed the diploma work on the moss flora in relation to environmental factors in alpine regions.

At the Institute for Evolutionary Biology and Environmental Studies Sabine Ragot (2011) studied in the group of Helmut Brandl in an interdisciplinary approach with botanists and geologists die microbial populations on apatite and the solubilization of phosphate from rock material from the apatite band in the region of the Piatto della Miniera above Lake di Dentro.

From time to time also students from other universities carried out their research at the Centre of Alpine Biology, from the University of Konstanz Stefan Wagener (PhD thesis 1989) worked on protozoa in the lower anoxic water layer and Markus Fritz (1995) started his investigations on volatile sulfur compounds in the bottom water. Martine Uhde (1991) from the ETHZ/EAWAG and the University of Freiburg i.Br. examined the mixing processes in the lake using sulfur hexafluoride as tracer. Alexis Walter (2006) from the University of Neuenburg explored with new methods extensively the bacterial mats in the wetland of Bolle di fuori.