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Precipitation of amorphous CaCO3 (aragonite-like) by cyanobacteria: A STXM study of the influence of EPS on the nucleation process

Title data

Obst, Martin ; Dynes, James J. ; Lawrence, John R. ; Swerhone, George D. W. ; Benzerara, Karim ; Karunakaran, Chithra ; Kaznatcheev, Konstantin V. ; Tyliszczak, Tolek ; Hitchcock, Adam P.:
Precipitation of amorphous CaCO3 (aragonite-like) by cyanobacteria: A STXM study of the influence of EPS on the nucleation process.
In: Geochimica et Cosmochimica Acta. Vol. 73 (2009) Issue 14 . - pp. 4180-4198.
ISSN 0016-7037
DOI: https://doi.org/10.1016/j.gca.2009.04.013

Abstract in another language

An amorphous or nanocrystalline calcium carbonate (ACC) phase with aragonite-like short-range order was found to be a transient precursor phase of calcite precipitation mediated by cyanobacteria of the strain Synechococcus leopoliensis PCC 7942. Using scanning transmission X-ray microscopy (STXM), different Ca-species such as calcite, aragonite-like CaCO3, and Ca adsorbed on extracellular polymers were discriminated and mapped, together with various organic compounds, at the 30 nm-scale. The nucleation of the amorphous aragonite-like CaCO3 was found to take place within the tightly bound extracellular polymeric substances (EPS) produced by the cyanobacteria very close to the cell wall. The aragonite-like CaCO3 is a type of ACC since it did not show either X-ray or electron diffraction peaks. The amount of aragonite-like CaCO3precipitated in the EPS was dependent on the nutrient supply during bacterial growth. Higher nutrient concentrations (both N and P) during the cultivation of the cyanobacteria resulted in higher amounts of precipitation of the aragonite-like CaCO3, whereas the amount of Ca2+ adsorbed per volume of EPS was almost independent of the nutrient level. After the onset of the precipitation of the thermodynamically stable calcite and loss of supersaturation the aragonite-like CaCO3 dissolved whereas Ca2+ remained sorbed to the EPS albeit at lower concentrations. Based on these observations a model describing the temporal and spatial evolution of calcite nucleation on the surface of S. leopoliensis was developed. In another set of STXM experiments the amount of aragonite-like CaCO3 precipitated on the cell surface was found to depend on the culture growth phase: cells in the exponential growth phase adsorbed large amounts of Ca within the EPS and mediated nucleation of ACC, while cells at the stationary/death phase neither adsorbed large amounts of Ca2+ nor mediated the formation of aragonite-like CaCO3. It is suggested that precipitation of an X-ray amorphous CaCO3 layer by cyanobacteria could serve as a protection mechanism against uncontrolled precipitation of a thermodynamically stable phase calcite on their surface.

Further data

Item Type: Article in a journal
Refereed: Yes
Additional notes: BAYCEER135573
Institutions of the University: Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Heisenberg Professorship - Experimental Biogeochemistry
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences > Heisenberg Professorship - Experimental Biogeochemistry > Heisenberg Professorship - Experimental Biogeochemistry - Univ.-Prof. Dr. Martin Obst
Research Institutions
Research Institutions > Research Centres
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Faculties
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Earth Sciences
Result of work at the UBT: No
DDC Subjects: 500 Science
500 Science > 550 Earth sciences, geology
Date Deposited: 13 Aug 2020 12:55
Last Modified: 15 Sep 2020 08:53
URI: https://eref.uni-bayreuth.de/id/eprint/56491