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Nested Formation of Calcium Carbonate Polymorphs in a Bacterial Surface Membrane with a Graded Nanoconfinement: An Evolutionary Strategy to Ensure Bacterial Survival.

  • Simon, Paul1
  • Pompe, Wolfgang2
  • Gruner, Denise3, 4
  • Sturm, Elena1, 5
  • Ostermann, Kai3
  • Matys, Sabine6
  • Vogel, Manja6
  • Rödel, Gerhard3
  • 1 Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Straße 40, 01187 Dresden, Germany. , (Germany)
  • 2 Institute of Materials Science, Technische Universität Dresden, Helmholtzstraße 7, 01069 Dresden, Germany. , (Germany)
  • 3 Institute of Genetics, Technische Universität Dresden, Zellescher Weg 20b, 01217 Dresden, Germany. , (Germany)
  • 4 Polymeric Microsystems, Technische Universität Dresden, Helmholtzstraße 100, 01069 Dresden, Germany. , (Germany)
  • 5 Physical Chemistry, University of Konstanz, POB 714, D-78457 Konstanz, Germany. , (Germany)
  • 6 Helmholtz Institute Freiberg for Resource Technology, Helmholtz-Zentrum Dresden-Rossendorf, Bautzener Landstraße 400, 01328 Dresden, Germany. , (Germany)
Published Article
ACS Biomaterials Science & Engineering
American Chemical Society (ACS)
Publication Date
Feb 14, 2022
DOI: 10.1021/acsbiomaterials.1c01280
PMID: 34995442


It is the intention of this study to elucidate the nested formation of calcium carbonate polymorphs or polyamorphs in the different nanosized compartments. With these observations, it can be concluded how the bacteria can survive in a harsh environment with high calcium carbonate supersaturation. The mechanisms of calcium carbonate precipitation at the surface membrane and at the underlying cell wall membrane of the thermophilic soil bacterium Geobacillus stearothermophilus DSM 13240 have been revealed by high-resolution transmission electron microscopy and atomic force microscopy. In this Gram-positive bacterium, nanopores in the surface layer (S-layer) and in the supporting cell wall polymers are nucleation sites for metastable calcium carbonate polymorphs and polyamorphs. In order to observe the different metastable forms, various reaction times and a low reaction temperature (4 °C) have been chosen. Calcium carbonate polymorphs nucleate in the confinement of nanosized pores (⌀ 3-5 nm) of the S-layer. The hydrous crystalline calcium carbonate (ikaite) is formed initially with [110] as the favored growth direction. It transforms into the anhydrous metastable vaterite by a solid-state transition. In a following reaction step, calcite is precipitated, caused by dissolution of vaterite in the aqueous solution. In the larger pores of the cell wall (⌀ 20-50 nm), hydrated amorphous calcium carbonate is grown, which transforms into metastable monohydrocalcite, aragonite, or calcite. Due to the sequence of reaction steps via various metastable phases, the bacteria gain time for chipping the partially mineralized S-layer, and forming a fresh S-layer (characteristic growth time about 20 min). Thus, the bacteria can survive in solutions with high calcium carbonate supersaturation under the conditions of forced biomineralization.

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