Micropearls as Bioremediation Agents – Microbials 2017

This project is one of the five winners of the call 2017 «Microbials – Direct Use of Micro-Organisms». Project partners: Department of Botany and Vegetal Biology, Department F-A Forel for Environmental and Aquatic Sciences, University of Geneva; Service de l'écologie de l'eau (SECOE), Geneva; Laboratorio di microbiologia applicata (ICM), Bellinzona; INRA- UMR CARRTEL, Thonon-les-Bains, France; Institute of Geosciences, Friedrich Schiller University Jena, Germany; Universidad Mayor San Andres (UMSA), Instituto de Investigaciones Biologicas, La Paz, Bolivia; Phytorestore, Paris, France

Project data

Project no: GRS-071/17
Amount of funding: CHF 325'000
Approved: 30.10.2017
Duration: 06.2018 - 12.2022
Area of activity: Microbials, seit 2016

Project management

Prof. Daniel Ariztegui
University of Geneva
Department of Earth Sciences
Rue des Maraichers 13
1205 Genève (Schweiz)
daniel.notexisting@nodomain.comariztegui@unige.notexisting@nodomain.comch

Project description

Recently certain microalgae have been discovered to form intracellular mineral inclusions called micropearls. They highly concentrate specific polluting elements (e.g. Sr and Ba) opening new possibilities to develop bioremediation techniques. This could be useful for example for waters polluted by radioactive strontium, which are produced in high quantities by accidents such as Chernobyl or Fukushima, but is also known as a major contaminant found in wastewater and sludges linked with nuclear activities. Organisms preferentially concentrating barium could be used for waters polluted by barium, linked to sludge deposits due to oil production.

These micropearls were first observed in Lake Geneva. The lake’s low concentration of pollutants uncovered these microalgaes extremely high concentration capacity. Preliminary laboratory tests further showed that these organisms are able to incorporate high concentrations of the polluting elements in only a few days. Moreover, they apparently survive in waters containing high quantities of the element they concentrate. Altogether these capacities elect these micropearl-forming organisms as very good candidates for the development of bioremediation methodologies.

The biomineralization process leading the organism to produce micropearls is not yet understood. The challenges are to 1) fully understand the biological process leading to the biomineralization of the micropearls; 2) identify the genes involved in the tolerance and the absorption of the polluting elements; and 3) implement a bioremediation application in natural environments.

What is special about the project?

This research addresses key questions concerning the environmental and internal conditions in which certain micro-organisms form intracellular mineral inclusions and concentrate polluting elements. Micropearls are a totally new feature in biology. Although some are produced by well-studied organisms (e.g. Tetraselmis cordiformis), they had been overlooked until end 2016. The mineralogy of micropearls is innovative in itself, as they show internal nanoscale concentric zonations which have never been observed in amorphous minerals before. Finally, the biological process leading to the biomineralization of micropearls has no known equivalent. To address this totally new topic, our interdisciplinary approach is a cross-over between geology, chemistry, biology and environmental sciences. Moreover, the possible bioremediation applications could be of great societal benefit.

Status/Results

In collaboration with the laboratory of Nuclear physics and chemistry of the Haute École du Paysage, D'ingénierie et D'architecture de Genève, we have demonstrated that T. chui presents high 90Sr uptake capacities, confirming its suitability for bioremediation applications to treat environments contaminated with this radionuclide. We performed several experiments with T. chui cultures containing the radioactive isotope 90Sr and we measured its uptake rate by T. chui cells. We developed an adapted technique to measure this radionuclide in the growth medium of the cultures using liquid scintillation counting. We have successfully sequenced the complete genome of T. chui and made its respective annotation. This achievement is of great relevance as it has never been done before and will allow the identification of genes related to micropearl formation. For that purpose, we are currently performing an RNA differential expression study of T. chui cultures grown under different culture conditions. The results obtained so far are promising and will be published shortly.

Thanks to the collaboration established with the laboratory of Marine biotechnology of The Algarve Centre of Marine Sciences (CCMAR-Algarve, Portugal), we optimized T. chui growth in 1L-bubble column photobioreactors and obtained a Sr (natural isotope) removal efficiency from seawater of 100%. Moreover, we discovered that CO2 injections accelerate algae growth and improve Sr uptake by the cells. These results are promising since this type of photobioreactor can be reproduced on a large/industrial scale and could be used simultaneously for atmospheric CO2 mitigation. T. chui has proven to be a robust species, able to reach high cell densities in environments with different salinities and pH, which is an essential requirement for an organism to be used as a bioremediation agent. Our results also suggest the use of other species within the genus Chlorodendrophycae for bioremediation purposes regarding 90Sr pollution since it has been shown that Sr uptake is related to micropearl formation (Segovia et al, 2022, under review).

Publications

Martignier A., Pacton M., Filella M., Jaquet J.-M., Barja F., Pollok K., Langenhorst F., Lavigne S., Guagliardo P., Kilburn M.R., Thomas C., Martini R. and Ariztegui D. (2017) Intracellular amorphous carbonates uncover a new biomineralization process in eukaryotes. Geobiology 15: 240-253.
Martignier, A., Filella, M., Pollok, K., Melkonian, M., Bensimon, M., Barja, F., Langenhorst, F., Jaquet, J.M., Ariztegui, D. (2018) Marine and freshwater micropearls: Biomineralization producing strontium-rich amorphous calcium carbonate inclusions is widespread in the genus Tetraselmis (Chlorophyta). Biogeosciences, 15, 6591-6605.
Martignier, A., De Respinis, S., Filella, M., Segovia, I., Marin, B., Günther, G., Barja, F., Tonolla, M., Jaquet, J.-M., Melkonian, M., Ariztegui, D. (2020): Biomineralization capacities of Chlorodendrophyceae: correlation between chloroplast morphology and the distribution of micropearls in the cell. Protist 171:125760.

Links

Research Group
Inés Segovia Campos at Université de Genève

Persons involved in the project

Prof. Daniel Aritzegui, project leader
Inés Segovia Campos, phd student
Francois Barja, lecturer, Department of Botany and Vegetal Biology, UNIGE
Karl Perron: Lecturer, Department of Botany and Vegetal Biology, UNIGE.
Montserrat Filella, lecturer, Department F-A Forel for Environmental and Aquatic Sciences, UNIGE
Jean-Michel Jaquet, guest scientist, Department of Earth Sciences, UNIGE
Agathe Martignier, SEM lab manager, Department of Earth Sciences, UNIGE (presently accomplishing her dissertation on the subject that is the base of this proposal)

External collaborations
Dario Acha: Professor/Director, Universidad Mayor San Andres (UMSA), Instituto de Investigaciones Biologicas, La Paz, Bolivia
Stephan Jacquet: Senior researcher, INRA, Thonon-les-Bains, France.
Mauro Tonolla: Head of the Laboratorio di microbiologia applicata (ICM), Bellinzona (Ti)
Luis Miguel Laglera Baquer: Professor/Head of Analytical Chemistry at Universitat de les Illes Balears (UIB)

Last update to this project presentation 17.01.2023

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