The role of cyanobacterial extracellular polymeric substances (EPS) in carbonate precipitation

Marlisa de Brito soutiendra sa thèse sur le rôle des cyanobactéries dans la précipitation des carbonates vendredi 29 septembre à 14 h 30 dans l’amphithéâtre Guyton de Morveau (3^e étage, aile sud).

Résumé

Cyanobacteria are major contributors to the precipitation of minerals forming biogenic carbonates through microbially-mediated mineralization processes (often called ‘organomineralization’). Their photosynthetic activity increases pH, favoring CaCO₃ precipitation. Additionally, these phototrophs produce copious amounts of exopolymeric substances (EPS) which can carry a net negative electric charge and have the capacity to bind metal ions including Ca²⁺, initially inhibiting precipitation. Upon alteration (including degradation) of EPS, Ca²⁺ is released and can precipitate as calcium carbonate. Alternatively, the Ca²⁺ bound on EPS can precipitate on the organic matrix. EPS properties are the result of its production and consumption and, thus, change constantly. Environmental conditions (e.g., including pH) impact the charger and binding capacity of EPS and consequently influence the properties of CaCO₃ crystals. The main objective of this thesis is to characterize and understand the role of cyanobacterial EPS in carbonate precipitation. For that, cyanobacterial growth patterns, quantity and quality of EPS produced were investigated as well as the effect of EPS produced in carbonate mineral formation in the laboratory (in vitro) and in the natural system (in situ).

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The role of cyanobacterial extracellular polymeric substances (EPS) in carbonate precipitation

Marlisa de Brito soutiendra sa thèse sur le rôle des cyanobactéries dans la précipitation des carbonates vendredi 29 septembre à 14 h 30 dans l’amphithéâtre Guyton de Morveau (3^e étage, aile sud).

 

Résumé

Cyanobacteria are major contributors to the precipitation of minerals forming biogenic carbonates through microbially-mediated mineralization processes (often called ‘organomineralization’). Their photosynthetic activity increases pH, favoring CaCO₃ precipitation. Additionally, these phototrophs produce copious amounts of exopolymeric substances (EPS) which can carry a net negative electric charge and have the capacity to bind metal ions including Ca²⁺, initially inhibiting precipitation. Upon alteration (including degradation) of EPS, Ca²⁺ is released and can precipitate as calcium carbonate. Alternatively, the Ca²⁺ bound on EPS can precipitate on the organic matrix. EPS properties are the result of its production and consumption and, thus, change constantly. Environmental conditions (e.g., including pH) impact the charger and binding capacity of EPS and consequently influence the properties of CaCO₃ crystals. The main objective of this thesis is to characterize and understand the role of cyanobacterial EPS in carbonate precipitation. For that, cyanobacterial growth patterns, quantity and quality of EPS produced were investigated as well as the effect of EPS produced in carbonate mineral formation in the laboratory (in vitro) and in the natural system (in situ).