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

Abstract

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.

Calcium carbonate: controlled synthesis, surface functionalization, and nanostructured materials

“…395 The ethanol both solubilizes the ligand and assists in the formation of kinetically stable ACC. Two main reactions successively occur, according to eqn (10) and (11). The PCDA chains are bound to the ACC core via chelation between their terminal -COOH groups and Ca 2+ ions.…”

“…1,2 In addition, CaCO 3 is present in many living organisms, functioning either as a structural support (e.g., in algae, 3 sponges, 4,5 corals 6 ), a form of protection (e.g., shells), 7 a hard buoyancy tank (e.g., cuttlebone), 8 or as a component in photoreceptor systems (e.g., light-focusing eye lenses of chitons and brittlestars). 9 CaCO 3 is also synthesized by bacteria, 10 even in extreme biomineralization conditions, 11 and is an essential component of mineralized tissues as in the apatitic whale bone. 12,13 Crystalline CaCO 3 exhibits three polymorphs: hexagonal vaterite, orthorhombic aragonite, and rhombohedral calcite, in order of increasing thermodynamic stability.…”

“…, light-focusing eye lenses of chitons and brittlestars). 9 CaCO 3 is also synthesized by bacteria, 10 even in extreme biomineralization conditions, 11 and is an essential component of mineralized tissues as in the apatitic whale bone. 12,13 Crystalline CaCO 3 exhibits three polymorphs: hexagonal vaterite, orthorhombic aragonite, and rhombohedral calcite, in order of increasing thermodynamic stability.…”

Bacterial templated carbonate mineralization: insights from concave-type crystals induced by Curvibacter lanceolatus strain HJ-1

“…In order to investigate the mechanisms of bacteria-induced carbonate precipitation, scientists have conducted numerous biomineralization experiments using different microorganisms, including sulfate-reducing bacteria, 17 anaerobic bacteria, 18 urea hydrolyzing bacteria, 19,20 thermophilic bacteria, 21 and cyanobacteria. 22,23 The aforementioned studies indicate that in bacteria-induced carbonate precipitation systems, bacteria influence/regulate the carbonate precipitation process through several aspects: bacterial activities can alter the physicochemical properties of the solution.…”

Multilevel Micronanoscale Texture Effects on Fly Wing Membrane–Water Droplet Interaction

“…Here, this raised an interesting issue about how to choose the correct surface coating method toward a substrate with a multilevel micronanoscale structure in changing a nonwettable surface to a wettable surface and revealing its mechanisms. Those experimental studies are less due to the difficulties in understanding the natural or mimetic wetting states in different theoretical models, , fabricating the wettable surface or nonwettable surface with a multilevel micronanoscale structure in a controllable route − and turning those examples into a more actual usage scenario. − …”