Biocontrolled soil nutrient distribution under the influence of an oxalogenic-oxalotrophic ecosystem

Pons, Sophie; Bindschedler, Saskia; Sebag, David; Junier, Pilar; Verrecchia, Éric P.; Cailleau, Guillaume

doi:10.1007/s11104-018-3573-1

Cited by 11 publications

(3 citation statements)

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“…Among our strains, only eight were able to solubilize inorganic phosphate, suggesting a minor contribution of the OCP fungi to the P cycle. This is in line with in situ measurements of phosphorus content in an OCP system, where this content was mostly influenced by soil depth but not by the OCP [62].…”

Section: Discussionsupporting

confidence: 89%

“…We reported here the first evidence of an active OCP in Madagascar. To date, the OCP has been observed in numerous tropical and semiarid environments, with different tree species, and across various geographical areas, such as Israel [ 60 ], the USA [ 61 ], Bolivia [ 30 ], India [ 23 ], Cameroon [ 62 ], the Ivory Coast [ 13 ], Haiti, and Mexico [ 63 ]. Here we identified T. indica as an oxalogenic tree driving an active OCP.…”

Section: Discussionmentioning

confidence: 99%

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Functional Diversity of the Litter-Associated Fungi from an Oxalate-Carbonate Pathway Ecosystem in Madagascar

et al. 2021

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The oxalate–carbonate pathway (OCP) is a biogeochemical process linking oxalate oxidation and carbonate precipitation. Currently, this pathway is described as a tripartite association involving oxalogenic plants, oxalogenic fungi, and oxalotrophic bacteria. While the OCP has recently received increasing interest given its potential for capturing carbon in soils, there are still many unknowns, especially regarding the taxonomic and functional diversity of the fungi involved in this pathway. To fill this gap, we described an active OCP site in Madagascar, under the influence of the oxalogenic tree Tamarindus indica, and isolated, identified, and characterized 50 fungal strains from the leaf litter. The fungal diversity encompassed three phyla, namely Mucoromycota, Ascomycota, and Basidiomycota, and 23 genera. Using various media, we further investigated their functional potential. Most of the fungal strains produced siderophores and presented proteolytic activities. The majority were also able to decompose cellulose and xylan, but only a few were able to solubilize inorganic phosphate. Regarding oxalate metabolism, several strains were able to produce calcium oxalate crystals while others decomposed calcium oxalate. These results challenge the current view of the OCP by indicating that fungi are both oxalate producers and degraders. Moreover, they strengthen the importance of the role of fungi in C, N, Ca, and Fe cycles.

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Section: Discussionsupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Functional Diversity of the Litter-Associated Fungi from an Oxalate-Carbonate Pathway Ecosystem in Madagascar

et al. 2021

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“…The microbial metabolism of oxalic acid exchanges a strong acid-oxalic acid (pK a 1 ¼ 1.25 and pK a 2 ¼ 4.27)-for a weak one-carbonic acid (pK a 1 ¼ 6.35 and pK a 2 ¼ 10.33)-which may lead to a strong local increase of pH. Such an influence on the soil pH prevents cation leaching from soil as a result of low pH (Pons et al, 2018) and can eventually promote the precipitation of calcium carbonate (CaCO 3 ) if pH increases above 8 (Aragno & Verrecchia, 2012;Verrecchia et al, 2006). In this latter process, for each mole of calcium oxalate oxidized, 1 mol of CO 2 is released in the atmosphere, while the other one is sequestered in soils as biomineralized CaCO 3 .…”

Section: Cell-to-cell Interactionsmentioning

confidence: 99%

Bacterial oxalotrophy as an alternative biocontrol approach for the fight against pulmonary aspergillosis

Palmieri¹

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Although fungi are estimated to kill more than 1.5 million people every year worldwide, the issue of fungal pathogenesis is largely neglected. Moreover, the rise of emergence of multi-resistant fungal pathogens worldwide is a major threat for human health. This is notably the case of the opportunistic fungal pathogens of the genus Aspergillus. The prevalence of Aspergillus-related infections, also known as aspergillosis, has dramatically increased in the last few years. Aspergillus species, such as A. fumigatus, A. flavus, A. nidulans, A. terreus or A. niger, are known to cause a vast spectrum of respiratory diseases, ranging from mild allergies to life-threatening invasive infections. Interestingly, the formation of calcium oxalate crystals has been previously reported in the latter cases. Oxalic acid is known to play a key role in the pathogenesis of plant fungal pathogens, such as for instance Sclerotinia sclerotiorum. However, a link between the production of oxalic acid and pathogenicity has not been made yet in the case of Aspergillus. Oxalic acid is commonly produced by soil fungi, along with other low molecular weight organic acids. In soils, oxalic acid generally occurs in the form of calcium oxalate crystals. Despite its chemical stability and low solubility, calcium oxalate is rarely found in the geological records, something that has been suggested to be the results of its metabolization by oxalotrophic bacteria. Oxalogenic fungi are known to interact with oxalotrophic bacteria in soils within the oxalate-carbonate pathway, where fungi, along with plants, are the source of oxalate, and oxalotrophic bacteria are its sink. Oxalotrophy is concomitant with a pH increase, which eventually leads to the precipitation of calcium carbonate, if the pH increases above a value of 8.4. The aim of the present thesis was to translate the metabolic interaction between oxalogenic fungi and oxalotrophic bacteria occurring in soils to human health. Specifically, we developed and assessed a novel biocontrol strategy for the treatment of pulmonary aspergillosis based on the manipulation of the environment through bacterial oxalotrophy, a process we named environmental interference. For this, the influence of the composition of the culture medium on the production of low molecular weight organic acids was tested for selected fungal strains, as well as their interaction with non-oxalotrophic and oxalotrophic bacterial strains. The fungal strain Aspergillus niger was selected because of its systematic production of oxalic acid in all culture media tested, and because of its medical relevance. The first demonstration of the principle of environmental interference in-vitro was made by showing the biocontrol exerted by the oxalotrophic bacterial species Cupriavidus oxalaticus on the growth of A. niger. The use of soil bacteria was shown to be problematic, as they induce important cellular damage. Therefore, the genome of C. oxalaticus was analyzed in order to better understand the oxalotrophy metabolism in this model bacterial species. This highlighted the presence of an operon containing all the genes that are required for the degradation of oxalate. These data will be used for the design of an entirely enzymatic degradation pathway of oxalate that will be more suitable as a potential therapeutic option. Finally, the fungal:fungal:bacterial interaction between A. niger, Candida albicans and C. oxalaticus was investigated. This interaction is relevant in the case of pulmonary co-infection in immunocompromised patients and patients suffering from cystic fibrosis. The interaction of both opportunistic fungal pathogens and the oxalotrophic bacterium depended on the inoculation mode (simultaneous versus sequential). To conclude, while the presented results on the biocontrol concept of environmental interference are promising, a preclinical in-vivo demonstration of this concept in a murine infection model is crucial for the development of a potential clinical application. Indeed, a more comprehensive approach by integrating the immune system is necessary in order to better comprehend the interplay between the host, the pathogen and the lung microbiota in disease development.

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Calcium oxalate and calcium cycling in forest ecosystems

Parsons

Attiwill

Uren

et al. 2021

Trees

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Biocontrolled soil nutrient distribution under the influence of an oxalogenic-oxalotrophic ecosystem

Cited by 11 publications

References 45 publications

Functional Diversity of the Litter-Associated Fungi from an Oxalate-Carbonate Pathway Ecosystem in Madagascar

Functional Diversity of the Litter-Associated Fungi from an Oxalate-Carbonate Pathway Ecosystem in Madagascar

Bacterial oxalotrophy as an alternative biocontrol approach for the fight against pulmonary aspergillosis

Calcium oxalate and calcium cycling in forest ecosystems

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