In-vitro synthesis of amorphous Mg-, Ca-, Sr- and Ba-carbonates:
what do we learn about intracellular calcification by cyanobacteria?
Nithavong Cam1, 2 Jean-François Lambert1, Karim Benzerara2,
Thomas Georgelin1, Maguy Jaber
1 Laboratoire de Réactivité des Surfaces, UMR 7197, CNRS & UPMC2 Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, UMR 7590, CNRS & UMPC, Muséum National d’Histoire Naturelle, IRD UMR 206
2
Cyanobacteria and mineralization
Photosynthetic bacteria
Riding R. (2006) Geobiology (4); 299:316
6 CO2 + 6 H2O → C6H12O6 + 6 O2
used to be considered as exclusively extracellular
important mineralization activity
3
Some cyanobacteria form intracellular carbonates
K. Benzerara et al. (2014) PNAS (111); 10933:10938
Cyanothece sp. PCC 7425
Synechococcus sp. PCC 63121 µm
4
Particularities of intracellular carbonates
Inclusions Ø:75-500 nm
Amorphous
E. Couradeau et al. (2012) Science (336); 6080, 459:462
Enriched in Sr and Ba
= 86
= 1370
Mg0.18Ca0.53Sr0.08Ba0.21CO3
Sr/Ca solidSr/Ca solution
Ba/Ca solidBa/Ca solution
5
Some properties of calcium carbonates
Partitioning 0.021 (X=Sr)0.012 (X=Ba)
Amorphous (ACC)
How does the cell stabilize the amorphous phase?
Calcite Aragonite
Dietzel M. et al.(2004)Tesoriero A. J. and Pankow J. F. (1996)
1.19 (X=Sr)1.5 (X=Ba)
X/Ca solid X/Ca solution
?
Where does come from the partitioning?
25 °C
3.31 x10-9 M2 4.57 x10-9 M2
M. Kellermeier et al. (2014)
2.32 x10-8 M2 SolubilityPlummer L. N. and Busenberg E. (1982)< <
6
CO32-Mg2+
Sr2+Ca2+
Ba2+
+ CO32- Abiotic carbonates
[Mg2+]= 10 mM [Ca2+]= 5.3 mM [Sr2+]= 0.8 mM [Ba2+]= 2.1 mM
Same Sr/Ca and Ba/Ca ratios as observed in cyanobacteria carbonates
Initial pH = 10.6
SIACC = 1.803SI = log (IAP/Ks)
[CO32-]= 10 mM
Procedure for carbonate precipitation
7
Similarities:
- size- poor crystallinity- composition
Elemental ratios in precipitates are same as in the solution
Mg0.16Ca0.51Sr0.05Ba0.28CO3Ø ≈ 200 nm
Poorly crystalline
Cam N. et al. (2015) Geochimica et Cosmochimica Acta (161); 36:49.
Abiotic carbonates like bacterial ones
8
Association of Mg with Sr or Ba helps amorphous phase stability
without Mg
without Sr without Ba
without Sr and Ba
Calcite
Poorly crystalline
Monohydrocalcite
SEM SEM
TEM TEM
Poorly crystalline
Substituants effect in carbonates precipitation
Cam N. et al. (2015) Geochimica et Cosmochimica Acta (161); 36:49.
9
H2O MgCO3 -> CO2+ MgO CaCO3 -> CO2+ CaO
~ 1 H2O per 1 CO3 unitAs observed in biotic and abiotic ACC L.Brečević and A.E. Nielsen (1989)
For further in abiotic ACC characterization
Mg0.16Ca0.51Sr0.05Ba0.28CO3·1.03H2O
Thermogravimetric analysis
Cam N. et al. (2015) Geochimica et Cosmochimica Acta (161); 36:49.
CO2
DTG
Heat flow
(derivative of the weight loss)
CO2
DTG
Heat flow
(derivative of the weight loss)
325°C 375°C
Exothermic event = Crystallization
Calcite
10
XRD
Thermogravimetric analysis
For further in abiotic ACC characterization
Cam N. et al. (2015) Geochimica et Cosmochimica Acta (161); 36:49.
11
Reproduce similar carbonates in an abiotic way is possible
Conclusions
no partitioning between Ca, Sr and Ba
≈ 1Sr/Ca solidSr/Ca solution
Ba/Ca solid Ba/Ca solution ≈ 1
Amorphous calcium carbonate
enrichment in Sr and Ba inside the cells
carbonates formation solution has same elemental ratios as the minerals
– size– poor crystallinity– composition
12
– pH = 10.64
– [Ca] = 5.3 mM
– [inorganic carbon] = 10 mM
About precipitation solution composition
Known chemistry of cyanobacteria intracellular medium is very different
– pH < 7.9
– [Ca]< 2.6µM
– [inorganic carbon] < 30 mM
Cyanobacteria intracellular medium
A. L. Barrán-Berdón et al. (2011)
M. R. Badger and T. J. Andrews (1982)
H.-B.Jiang et al. (2013)
SIACC = -2.225 no precipitation SIACC = 1.803
what we know about cyanobacteria intracellular composition can not explain the precipitation of calcium carbonate
Abiotic synthesis medium
13
Thank you for attention
This work was supported by French state funds managed by the ANR within the Investissements d'Avenir programme under reference ANR-11-IDEX-0004-02, and more specifically within the framework of the Cluster of Excellence MATISSE
G. Morin, F. Skouri-Panet and M. Poinsot (IMPMC)Acknowledgment:
K.Benzerara was supported by ERC grant (Calcyan)