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Institut de minéralogie, de physique des matériaux et de cosmochimie


Cyanobacteria are environmentally important photosynthetic organisms that use solar energy to fix atmospheric CO2 thereby making up a huge biomass that sustains a large part of the food chain of our planet. As recently discovered, some cyanobacteria form intracellular amorphous calcium carbonates (iACC), and accumulate very high intracellular contents of alkaline earth elements (AEEs) such as Ca, Sr, Ba or Ra (Couradeau et al., 2012 ; Benzerara et al., 2014[link 1] ). While this massive intracellular AEE accumulation questions the peculiarity of AEE homeostasis in these bacteria and offers promising perspectives to remediate radioactive 90Sr and 226Ra pollutions (Mehta et al., 2020[link 2] ), the mechanisms remain unknown. Based on a comparative genomics approach, we recently identified one gene with unknown function that may contribute to AEE sequestration, as it is shared by iACC-forming cyanobacteria and absent from the other fully-sequenced cyanobacterial genomes. The HARLEY project proposes to decipher the biochemical mechanisms of intracellular hyperaccumulation of AEEs by iACC-forming cyanobacteria and the role of the identified unknown gene in this process.

The Harley project will be carried out by a highly cohesive and interdisciplinary consortium grouping expertise in biochemistry, structural biology, biophysics, biogeochemistry, genetics and physiology of cyanobacteria. Our work program will consist in (1) characterizing in vitro structural and chemical properties of the protein encoded by the unknown gene. (2) characterizing the in vivo function of this protein and its role in AEE accumulation based on genetics. (3) searching for additional proteins involved in iACC formation. In addition to tackling the important issue of AEE homeostasis in these cyanobacteria and the biochemical mechanisms of iACC formation, results by the Harley project will be of great interest to structural biologists by the determination of novel protein folds and associated functions as well as cyanobacteriologists by the production of new genetic models. In the longer term, the Harley project will be crucial for designing new biomimetic or synthetic systems of value for an effective bioremediation of AEEs pollutions.


Start and duration of the scientific project: January 2020 - 48 Months

Coordinateur : Karim Benzerara

Useful links

- Site ANR (ANR-19-CE44-0017)

- Une bactérie pour dépolluer des effluents radioactifs - Actu CNRS-INSB - 19/02/2020

- Zoom Science - Un piège bactérien à strontium et baryum - Juin 2018

- Zoom Science - Janvier 2015 - Comment les cyanobactéries du monde entier forment-elles des carbonates ?


References :

“Intracellular Ca-carbonate biomineralization is widespread in cyanobacteria“
Benzerara K., Skouri-Panet F., Li J., Férard C., Gugger M., Laurent T., Couradeau E., Ragon M.,  Cosmidis J., Menguy N., Margaret-Oliver I., Tavera R., López-García P., and Moreira D.
2014, Proc. Natl. Acad. Sci. USA 111, 10933-10938

“An early-branching microbialite cyanobacterium forms intracellular carbonates”
Couradeau E., Benzerara K., Gérard E., Moreira D., Bernard S., Brown Jr. GE., López- García P.
2012. Science, 336, 459-462.

“16 S rDNA-based analysis reveals cosmopolitan occurrence but limited diversity of two cyanobacterial lineages with contrasted patterns of intracellular carbonate mineralization“
Ragon M., Benzerara K., Moreira D., Tavera R. and López-García P.
2014. Frontiers in Microbiology, 5, #331.



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