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The oxalate-carbonate pathway: measuring biological interactions and dynamics in a natural C sink ecosystem

English title The oxalate-carbonate pathway: measuring biological interactions and dynamics in a natural C sink ecosystem
Applicant Junier Pilar Eugenia
Number 137994
Funding scheme Interdisciplinary projects
Research institution Laboratoire de Microbiologie Institut de Biologie Université de Neuchâtel
Institution of higher education University of Neuchatel - NE
Main discipline Other disciplines of Environmental Sciences
Start/End 01.01.2012 - 31.12.2013
Approved amount 300'000.00
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Keywords (6)

Oxalate; Carbonate; Bacteria; Fungi; Calcium; Carbon sink

Lay Summary (English)

Lead
Lay summary

The formation of calcite in otherwise carbonate-free acidic soils through the biological degradation of oxalate is a mechanism termed oxalate-carbonate pathway, which occurs during interaction between biological and geological systems. In this pathway, atmospheric CO2 is fixed by the photosynthetic activity of plants, part of which is destined to the production of oxalate to control the intracellular Ca2+ concentrations. An additional source of calcium oxalate is fungi, which are able to produce this organic acid to cope with elevated concentrations of metals. The decay of plant material results in a source of calcium oxalate for other trophic levels. In spite of its abundance as a substrate, oxalate is a very stable organic anion that can be metabolized only by a group of bacteria that use it as a carbon and energy source. These bacteria close the biological cycle by degrading calcium oxalate, releasing Ca2+ and changing the local soil pH. If the conditions are adequate, the geological part of the pathway begins because this biological process will indirectly lead to the precipitation of secondary calcium carbonate (calcite) under unexpected geological settings. 

The activity of the oxalate-carbonate pathway has now been demonstrated in several places around the world. Furthermore, it can constitute an important, although underestimated, soil mineral carbon sink. This is because due to the initial acidic soil conditions and the absence of geological carbonate in the basement, it is unexpected to find C in the form of calcite. By its global scale and its stability through a long period of time, this terrestrial C sink is of a crucial interest as the sustainability of other C sequestering processes (e.g. sinking of CO2 in the ocean) is under question.

The study of the oxalate-carbonate pathway constitutes a multidisciplinary research that brings together competences in biology (botany, physiology, microbiology) and geology (geochemistry, mineralogy, soil science). Thus, from its inception, this research has been carried out by a multidisciplinary team and by combining two crucial aspects: field expeditions and laboratory work using several tropical soils as models. Our most recent results show that biological interactions between bacteria and fungi, that have been underestimated, are essential for reproducing the pathway in vitro. Also, we have observed that Ca budget/availability has a direct impact on pedogenic carbonate accumulations.

Therefore, the aims of this proposal are twofold: first, we aim at elucidating the nature of the interaction between bacteria and fungi and its importance for the oxalate-carbonate pathway. Second, we aim at understanding how the Ca cycle (pools, fluxes and limitations in the concentration of Ca2+) can drive an “ecosystem induced-C sink”, in our case the oxalate-carbonate pathway system.

By pursuing these two objectives, we expect to contribute essential information within two of the current “black boxes” of the system, which will allow the establishment of a model of the dynamics of carbon accumulation associated with the oxalate-carbonate pathway. This may have an enormous impact due to the potential importance of this ecosystem (or equivalent ecosystems) in tackling the increasing atmospheric CO2 concentrations and their direct effect over global climate.

Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Isolation and characterization of oxalotrophic bacteria from tropical soils.
Bravo Daniel, Braissant Olivier, Cailleau Guillaume, Verrecchia Eric, Junier Pilar (2015), Isolation and characterization of oxalotrophic bacteria from tropical soils., in Archives in Microbiology, 197, 65-77.
Detection of active oxalate-carbonate pathway ecosystems in the Amazon Basin: global implications of a natural potential C sink
Cailleau G., Mota M., Bindschedler S., Junier P., Verrecchia E.P. (2014), Detection of active oxalate-carbonate pathway ecosystems in the Amazon Basin: global implications of a natural potential C sink, in Catena, 116, 132-141.
Identification of active oxalotrophic bacteria by Bromodeoxyuridine DNA-labeling in a microcosm soil experiments
Bravo Daniel, Martin Gaetan, David Maude M., Cailleau Guillaume, Verrecchia Eric, Junier Pilar (2013), Identification of active oxalotrophic bacteria by Bromodeoxyuridine DNA-labeling in a microcosm soil experiments, in FEMS Microbiology Letters, 348, 103-111.
Isolation of oxalotrophic bacteria able to disperse on fungal mycelium
Bravo Daniel, Cailleau Guillaume, Bindschedler Saskia, Simon Anaele, Job Daniel, Verrecchia Eric, Junier Pilar (2013), Isolation of oxalotrophic bacteria able to disperse on fungal mycelium, in FEMS Microbiology Letters, 348, 157-166.

Collaboration

Group / person Country
Types of collaboration
Greenloop Belgium (Europe)
- Industry/business/other use-inspired collaboration
Association Racines Switzerland (Europe)
- Industry/business/other use-inspired collaboration
Lukas Y. Wick Germany (Europe)
- Publication
- Research Infrastructure
Nérée Awana Onguéné Cameroon (Africa)
- in-depth/constructive exchanges on approaches, methods or results
Olivier Braissant Switzerland (Europe)
- Publication
- Research Infrastructure

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
Bacterial-fungal interactions Poster Applying the "fungal highways" concept as an approach to identify fungal-bacterial associations in natural ecosystems 07.12.2013 Roscoff, France Job Daniel; Verrecchia Eric; Junier Pilar Eugenia; Simon Anaele;
Bacterial-fungal interactions Talk given at a conference Fungal control of dispersion and activity of bacteria in unsaturated environments 07.12.2013 Roscoff, France Job Daniel; Simon Anaele; Junier Pilar Eugenia;
XXXV Meeting of the Chilean Microbiology Society Talk given at a conference Fungal control of dispersion and activity of bacteria in unsaturated environments 25.11.2013 Maintencillo, Chile Junier Pilar Eugenia; Job Daniel; Simon Anaele;
Swiss Geoscience Meeting Individual talk When a century is enough to invert a million years pedogenesis: the oxalate carbonate pathway in tropical agro-ecosystems 15.11.2013 Lausanne, Switzerland Junier Pilar Eugenia; Verrecchia Eric; Cailleau Guillaume;
Soil Space and Time Individual talk Calcium biogeochemical cycle within the oxalate carbonate pathway in tropical soils 30.09.2013 Ulm, Germany Verrecchia Eric; Junier Pilar Eugenia; Cailleau Guillaume;
5th Congress of European Microbiologist Poster Fungal highways in natural ecosystems, a new approach 21.07.2013 Leipzig, Germany, Germany Job Daniel; Verrecchia Eric; Junier Pilar Eugenia; Simon Anaele;
Swiss Microbial Ecoloby Meeting 2013 Talk given at a conference Identification of active oxalotrophic bacteria by BrdU labeled-DNA and their importance in the oxalate-carbonate pathway in natural environments 04.02.2013 Murten, Switzerland Verrecchia Eric; Job Daniel; Junier Pilar Eugenia;
Swiss Microbial Ecology Meeting 2013 Talk given at a conference Abundance, diversity and activity of fungal highways in natural ecosystems - A new approach 04.02.2013 Murten, Switzerland Simon Anaele; Junier Pilar Eugenia; Verrecchia Eric; Job Daniel;
Symposium in Fungi-Bacteria Interactions Talk given at a conference Fungal control of dispersion and activity of bacteria in unsaturated environments 11.10.2012 Neimegen, Netherlands Verrecchia Eric; Cailleau Guillaume; Junier Pilar Eugenia; Job Daniel; Simon Anaele;


Knowledge transfer events

Active participation

Title Type of contribution Date Place Persons involved
Journées lémaniques Talk 12.09.2013 Ngaoundéré, Cameroon Cailleau Guillaume;


Communication with the public

Communication Title Media Place Year
Talks/events/exhibitions Turning sunlight into stone: the oxalate-carbonate pathway in tropical ecosystems Western Switzerland 2012

Awards

Title Year
Best Poster Award 2013

Associated projects

Number Title Start Funding scheme
149853 Environmental factors limiting the interaction of bacteria and fungi in the context of the oxalate-carbonate pathway 01.01.2014 Interdisciplinary projects
172944 Assessing the coupled cycles of C and Ca in tropical environments: the significance of terrestrial carbonate deposits in limestone-free watersheds 01.10.2017 Project funding
118130 The role of plants, bacteria, and fungi in carbon transfer from atmospheric CO2 to calcium carbonate through the oxalate-carbonate pathway 01.11.2007 Interdisciplinary projects

Abstract

The formation of calcite in otherwise carbonate-free acidic soils through the biological degradation of oxalate is a mechanism termed oxalate-carbonate pathway, which occurs during interaction between biological and geological systems. In this pathway, atmospheric CO2 is fixed by the photosynthetic activity of plants, part of which is destined to the production of oxalate to control the intracellular Ca2+ concentrations. An additional source of calcium oxalate is fungi, which are able to produce this organic acid to cope with elevated concentrations of metals. The decay of plant material results in a source of calcium oxalate for other trophic levels. In spite of its abundance as a substrate, oxalate is a very stable organic anion that can be metabolized only by a group of bacteria that use it as a carbon and energy source. These bacteria close the biological cycle by degrading calcium oxalate, releasing Ca2+ and changing the local soil pH. If the conditions are adequate, the geological part of the pathway begins because this biological process will indirectly lead to the precipitation of secondary calcium carbonate (calcite) under unexpected geological settings. Because of the inter-relationship between trees, fungi, bacteria, and the environmental setting, this pathway can also be considered an ecosystem.The activity of the oxalate-carbonate pathway has now been demonstrated in several places around the world. Furthermore, it can constitute an important, although underestimated, soil mineral carbon sink. This is because due to the initial acidic soil conditions and the absence of geological carbonate in the basement, it is unexpected to find C in the form of calcite. By its global scale and its stability through a long period of time, this terrestrial C sink is of a crucial interest as the sustainability of other C sequestering processes (e.g. sinking of CO2 in the ocean) is under question.The study of the oxalate-carbonate pathway constitutes a multidisciplinary research that brings together competences in biology (botany, physiology, microbiology) and geology (geochemistry, mineralogy, soil science). Thus, from its inception, this research has been carried out by a multidisciplinary team and by combining two crucial aspects: field expeditions and laboratory work using several tropical soils as models. Our most recent results show that biological interactions between bacteria and fungi, that have been underestimated, are essential for reproducing the pathway in vitro. Also, we have observed that Ca budget/availability has a direct impact on pedogenic carbonate accumulations.Therefore, the aims of this proposal are twofold: first, we aim at elucidating the nature of the interaction between bacteria and fungi and its importance for the oxalate-carbonate pathway. Second, we aim at understanding how the Ca cycle (pools, fluxes and limitations in the concentration of Ca2+) can drive an “ecosystem induced-C sink”, in our case the oxalate-carbonate pathway system. By pursuing these two objectives, we expect to contribute essential information within two of the current “black boxes” of the system, which will allow the establishment of a model of the dynamics of carbon accumulation associated with the oxalate-carbonate pathway. This may have an enormous impact due to the potential importance of this ecosystem (or equivalent ecosystems) in tackling the increasing atmospheric CO2 concentrations and their direct effect over global climate.
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