Microbial Ecology - Lake Cadagno
Microbial Ecology - Lake Cadagno
The research is centred on the microbial ecology of the anoxygenic phototrophic sulfur bacteria living in the depth, water column (chemocline and monimolimnion) and in the sediments (microbial mats), of the meromictic Lake Cadagno. Especially in the oxic-anoxic transition zone, known as chemocline, the presence of light and hydrogen sulfide promotes the development of an abundant community of anaerobic phototrophic sulfur bacteria

Our main focus

The microbial ecology group at the LMA-SUPSI is mainly involved with the following tasks: 1) inter- and intra-seasonal monitoring of the Lake Cadagno water column, 2) eco-physiological studies using the anaerobic phototrophic sulfur bacteria of the chemocline, and 3) provides the necessary scientific and technical assistance to the Alpine Biology Centre (CBA) foundation in Piora. 

  1. Dynamics and evolution of the microbial populations in Lake Cadagno - During the last 25 years, the microbial populations and the Physico-chemical profiles of the Lake Cadagno water column are monitored continuously. The dynamics of bacterial populations, primarily anaerobic phototrophic sulfur bacteria of the chemocline, is fundamental for the structure and biological activity of the lake.

  2. Eco-physiology of anaerobic phototrophic sulfur bacteria - In the chemocline of Lake Cadagno, light irradiation, oxygen, and sulfur gradients favor the flourishing of a large community of anaerobic phototrophic sulfur bacteria. The most important populations are the purple sulfur bacteria (PSB) big-celled Chromatium okenii and small-celled Thiodictyon syntrophicum, and the green sulfur bacterium (GSB) Chlorobium phaeobacteroides. Every single bacterial population living in this ecological niche is subjected to physical and biological stress factors that presuppose survival and persistence strategies. Precisely because of the photosynthetic activity of the sulfur band located at a depth of about 12 meters in the oxy-anoxic transition zone of the lake, the Cadagno can support the presence of much more fish than in a typical alpine lake, making it very popular with fishers.

  3. Scientific support to the CBA - The coordination of scientific and educational activities at the CBA concerning microbiology issues. In particular, LMA provides scientific, logistical, and organizational advice and support to Swiss and foreign institutions active during the summer season at the CBA.

Group Members

Nicola Storelli (Group leader)

Mauro Tonolla (Professor SUPSI and UNIGE)

Samuele Roman (Technician and custodian CBA)

Francesco Di Nezio (PhD-Student)

Antoine Buetti-Dinh (Scientist) 


Current Projects

  • Bioconvection-mediated microbial ecophysiology in aquatic systems: Multi-scale dynamics in the chemocline of meromictic Lake Cadagno (BIOCAD) - In the permanently stratified waters of the Lake Cadagno, in Val Piora, lives a population of bacteria that, thanks to their synchronized movement, can cause the mixing of large volumes of water (up to 1m). This phenomenon is known as bioconvection and has never been studied in a natural environment before. The motile large-celled PSB Chromatium okenii can mix considerable volumes of water, not shaking it directly with their flagella but grouping in search of light in a small area near the front of oxygen diffusion. In this way, the density per volume increases, and the water begins to fall, taking the microorganisms with it. The main objective of the BIOCAD project, funded by the Swiss National Research Fund, is to study the effects of the bioconvection process on the eco-physiology of key microbial species in anaerobic aquatic environments. At the end of this project we can lay the foundations for understanding the consequences of bioconvection on the entire ecosystem of Lake Cadagno and use it as a model for describing similar phenomena in other environments. 

  • Sequencing of new genomes isolated from the meromictic Lake Cadagno - Genetic knowledge is necessary to better understand its specific role of each microorganism in the ecosystem of Lake Cadagno or more generally in general ecological processes.  

Bachelor and Master course UNIGE

Image Bachelor and Master course UNIGE

Lessons in biology at UNIGE (academic year 2019-20):

►Online (Zoom) the 1st and 2nd of July

  • 14B641_Hydrobiologie microbienne: Ecologie microbienne et écologie alpine (page 171) – The practical internship, lasting five days, is structured in theoretical and practical parts: lessons and didactic material accompany the practical work on Lake Cadagno and in the field (physical, chemical and biological analysis; in situ hybridization, flow cytometry, etc.). The emphasis is on the detection and typing of microorganisms and their ecological role in the biogeochemical cycles of matter.



Doctoral school CUSO (year 2020):

  • Field course Lake Cadagno - This 5-day activity aims at offering the students the required training by combining field activities with the development of a practical project that can be accomplished in the field. This will be complemented by presentations and discussion (by the students and participants) related to topics linked to the environment under study (Lake Cadagno and its catchment area in the Piora region, Tessin).


Information and documents from 2018-19 (last year):

Open position

We are open to the possibility to involve students for internship periods (minimum one month) or Bachelor/Master projects related to microbial ecology, in particular related to the meromictic Lake Cadagno. For any additional information or questions, contact Nicola Storelli.




Master projects


to be defined personally with the student.



Last publications

  • Luedin SM, Storelli N, Danza F, Roman S, Wittwer M, Pothier JF, Tonolla M (2019) Mixotrophic Growth Under Micro-Oxic Conditions in the Purple Sulfur Bacterium “Thiodictyon syntrophicum.” Front Microbiol 10:384 . doi: 10.3389/fmicb.2019.00384
  • Luedin SM, Liechti N, Cox RP, Danza F, Frigaard N-U, Posth NR, Pothier JF, Roman S, Storelli N, Wittwer M, Tonolla M (2019) Draft Genome Sequence of Chromatium okenii Isolated from the Stratified Alpine Lake Cadagno. Sci Rep 9:1936 . doi: 10.1038/s41598-018-38202-1
  • Danza F, Ravasi D, Storelli N, Roman S, Lüdin S, Bueche M, Tonolla M (2018) Bacterial diversity in the water column of meromictic Lake Cadagno and evidence for seasonal dynamics. PLoS One 13:e0209743 . doi: 10.1371/journal.pone.0209743
  • Luedin SM, Pothier JF, Danza F, Storelli N, Frigaard N-U, Wittwer M, Tonolla M (2018) Complete genome sequence of “Thiodictyon syntrophicum” sp. nov. strain Cad16T, a photolithoautotrophic purple sulfur bacterium isolated from the alpine meromictic Lake Cadagno. Stand Genomic Sci 13:14 . doi: 10.1186/s40793-018-0317-z
  • Danza F, Storelli N, Roman S, Lüdin S, Tonolla M (2017) Dynamic cellular complexity of anoxygenic phototrophic sulfur bacteria in the chemocline of meromictic Lake Cadagno. PLoS One 12:e0189510 . doi: 10.1371/journal.pone.0189510
  • Sommer T, Danza F, Berg J, Sengupta A, Constantinescu G, Tokyay T, Bürgmann H, Dressler Y, Sepúlveda Steiner OR, Schubert CJ, Tonolla M, Wüest A (2017) Bacteria-induced mixing in natural waters. Geophys Res Lett. doi: 10.1002/2017GL074868
  • Tonolla M, Storelli N, Danza F, Ravasi D, Peduzzi S, Posth NR, Cox RP, Jørgensen MF, Gregersen LH, Daugbjerg N, Frigaard N-U (2017) Lake Cadagno: Microbial Life in Crenogenic Meromixis. Springer International Publishing, pp 155–186

Past group members

Clarisse Beney (MSc-Student 2018-2019)

Francesco Danza (PhD student 2013-2018)

Samuel Lüdin (PhD student 2013-2018)

Pietro Tenti (MSc-Student 2017-2018)


Past Projects

  • Clarisse Beney, from the University of Geneva, did her master's work from September 2018 to October 2019. The aim of her project was to analyse the different oxidation rate of sulfide (H2S) and the effectiveness of carbon dioxide (CO2) assimilation for the most important populations of anaerobic phototrophic sulfur bacteria living in the chemocline of Lake Cadagno, i.e. the purple bacteria (PSB) Chromatium okenii LaCa, Thiodictyon syntrophicum Cad16T and the green beating (GSB) Chlorobium pheobacteroides.