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Biomineralization is a process in which mineral products ( biominerals ) are created as a result of the life activity of organisms . The ability to biomineralize is almost as old as life on earth ( originated with the first prokaryotes in the Archean ) and is subject to an evolutionary process that is just as long. The associated ongoing optimization of the mineralization processes has led to results that are increasingly interesting for science and technology ( bionics ).

Biomineralization can be divided into the following three basic types: precipitation and oxidation reactions, reactions that produce perfectly crystallized minerals and reactions that lead to “composite materials”. The last-mentioned type of reaction is generally given the greatest attention, so that it can be described as “biomineralization in the narrower sense”.

Precipitation and oxidation reactions

These are comparatively simple reactions in which dissolved substances are converted into undissolved substances by the metabolic activity of microorganisms.

Precipitation of lime (formation of stromatolites)

The oldest stromatolites were formed by cyanobacteria about 3.5 billion years ago and are therefore among the oldest evidence of life on earth. As autotrophic organisms, they consume carbon dioxide and thereby precipitate calcium carbonate according to the following reaction:

This results in the formation of pillow-shaped or bulbous limescale deposits, which are also supported by clay-like and silt-like sediments. For the organisms, the advantage of this type of biomineralization is probably that it creates a solid foundation on which they can stand as “bio mats” even under adverse weather conditions.

Precipitation of iron (III) oxide hydrate (FeO (OH))

Mineralized specimens of Gallionella ferruginea in the corrosion product of a gray cast iron pipe for drinking water, image section: 1.7 × 2.5 mm

In an environment in which the oxidation of dissolved iron (II) ions takes place slowly by purely chemical means, some microorganisms can accelerate the oxidation of iron ions by means of oxygen or nitrate. The oxidation with nitrate proceeds according to the following reaction equation:

The iron (III) oxide hydrate is deposited on the structures of the microorganisms, a process known as "mineralization". As chemoautotrophic bacteria, the organisms involved gain the energy they need to maintain their life processes. Deposits of iron (III) oxide and hydrate oxide are common in nature. These can be products of biomineralization. However, it is difficult to prove that this is the case in individual cases because iron (II) ions can be oxidized under favorable conditions without the aid of microorganisms. In individual cases, however, the structure of the mineralized microorganisms - as the picture "Mineralized specimens of Gallionella ferruginea ..." shows, is so clearly recognizable that there is no doubt about the biomineralization in this case.

Ribbon iron ores were also created through the activity of oxygen-releasing microorganisms .

Precipitation of manganese (IV) oxide

Manganese (IV) oxide, 2 × 3 mm, developed as a biofilm on quartz gravel in the demanganisation filter of a waterworks (shrinkage cracks when drying)

Manganese (II) ions can only be oxidized to manganese (IV) oxide with oxygen:

The energy yield of this reaction is so low that it is not sufficient to maintain the life processes. Manganese (IV) oxide is, however, a good adsorbent for nutrients, which accumulate in the immediate vicinity of the organisms. This creates an indirect benefit for the microorganisms. The manganese nodules are spectacular results of the biomineralization of manganese (IV) oxide .

The precipitation of manganese (IV) oxide by microorganisms is the cheapest and at the same time the most effective way of eliminating dissolved manganese in waterworks in the context of drinking water treatment.

Deposition of pyrite and marcasite

Pyrite, framboidal, 0.9 × 1.2 mm, originated in fossil wood in an aquifer in the city of Hanover

In aquifers that contain fossil organic matter, microorganisms can reduce sulfate. In the presence of iron (II) ions, iron disulfides ( marcasite , pyrite ) can be formed. This reaction takes place at a very slow rate (half-life: approx. 76 to 100 years). The following reaction equation should clarify this type of biomineralization:

The reducing agent is the cellulose content in the fossil organic matter, here simply represented as carbon (C). This reaction gives rise to poorly crystallized products (e.g. "framboidal pyrite"). The microorganisms involved gain the energy for their life processes with the sulfate reduction. The deposition of marcasite or pyrite is an important partial reaction in the self-cleaning processes in aquifers that contain fossil organic matter.

Reactions that produce perfectly crystallized minerals


Ice is considered a mineral with a comparatively low melting point. It can be dangerous for all living beings if they cannot actively protect themselves against freezing, like warm-blooded organisms. In the course of evolution, two strategies have developed with which the organisms can defend themselves: Some fish prevent their body fluids from freezing with antifreeze proteins . Certain species of frogs and turtles use the opposite tactic: They enrich their blood with proteins ("ice nucleation proteins") that promote freezing and control it in such a way that their cells are not damaged. Some bacteria also produce proteins that promote ice formation. Suspensions of Pseudomonas syringae have therefore already been used to produce artificial snow.

Calcium carbonate

Water- clear calcite crystals have - depending on the optical axis - a refractive index of 1.6584 or 1.4864. Calcite is therefore suitable as a material for the manufacture of lenses. The starfish Ophioma wentii has eyes with optically correctly oriented calcite microlenses that are distributed over the entire body. Optical calcite lenses were already using some species of trilobites around 350 million years ago . Her eyes consisted of up to 15,000 individual lenses. Calcium carbonate can also be helpful for hearing and the sense of balance: Zebrafish use auditory stones made of aragonite , which they shape with the help of "Starmaker proteins" so that they optimally fulfill their purpose.


Electron microscope image of Magnetospirillum gryphiswaldense cells with chains of magnetite crystals

Magnetite , a black iron oxide with the formula Fe 3 O 4, has, as the name suggests, ferromagnetic properties. This mineral was first found in living organisms when studying magnetotactic bacteria, i.e. microorganisms that orient their own movement to the field lines of the earth's magnetic field (e.g. Magnetospirillum gryphiswaldense or Magnetospirillum magnetotacticum ). The magnetite crystals, the magnetosomes, are enclosed by a membrane and are arranged in a chain-like structure that is enforced by a special protein. In contrast to abiotic magnetite, the crystals themselves are completely free of defects in the crystal lattice. The defined size of the crystals of approx. 45 nm causes their uniform magnetic moment ( single-domain crystals ).

The ability known as magnetotaxis offers the microorganisms, which are adapted to the oxygen deficiency of water sediments, the advantage that they can find the shortest path into the sediments along the field lines. Magnetosomes have also been discovered in higher animals that cover long distances on their migrations, for example in migratory birds, trout and salmon.

Production of "composite materials"

With composite materials , people have been able to combine materials with different properties in such a way that new types of materials are created for centuries. The best-known technical composite material is reinforced concrete , in which the compressive strength of the concrete is combined with the tensile strength of the steel. In living nature, materials that are principally composite materials have been widespread for several hundred million years. The inorganic component of these biomaterials is usually deposited in very small particle sizes. Therefore, from a materials science point of view, they can be regarded as “nanocomposite material” or “nanostructured hybrid material”. The material of bones and tooth enamel as well as the shells of eggs, clams and diatoms are well-known examples.

Scientists try to carefully separate the components of natural “composite materials” and analyze them separately. In this way, the structure and function of the substances can be clarified step by step. An answer to the question of the means by which organisms intervene in the material balance of their environment in order to carry out biomineralization is still a long way off.

Calcium carbonate

Weathered fossil rubble lime dominated by cockle housing flaps, built in the Temple of Zeus at Olympia .
Fungia , a flat-growing solitary coral.

As a component of biological “composite materials”, calcium carbonate (“lime”) plays a role in the shells of unicellular organisms ( foraminifera ) and numerous marine invertebrates as well as in the shells of bird eggs. No biomineralization product achieves a greater global turnover than calcium carbonate: The calcareous residues of dead organisms occur as rock-forming, in the form of fine-grain offshore limestones (e.g. " chalk ") or fossil rubble limestones formed near the coast. When fossil rubble limestones weather, the structures of the limestone skeletons they contain are often carved out on the rock surface. Animals that put on a calcareous shell, such as foraminifera and other unicellular organisms, as well as mussels, snails and other invertebrates, use it to protect their sensitive soft bodies.

It can be assumed that the oldest protective covers in the history of development consisted only of proteins. Most snakes and lizards today still lay eggs with flexible protein shells. In the line of development that leads to today's birds, it has proven expedient to store calcium carbonate in the shells. This increased the stability of the egg shell. The embryo was better protected, which increased its chances of survival until hatching.


  • Mother-of-pearl is an iridescent form of aragonite (rhombic crystallized calcium carbonate), which is formed by numerous sea snails and mussels.
  • Sea urchins use calcium carbonate to form shells, biting tools and spines. Sea urchin spines can be over ten centimeters long and attain a strength that exceeds that of purely inorganic calcium carbonate by several orders of magnitude. Other echinoderms also have skeletons or skeletal elements made of calcium carbonate.
  • The polyps of the hard corals secrete an exoskeleton on the basis of calcium carbonate. The typical compact or branched structures result from the joint separation activity of many very small polyps in a coral colony or the lime separation of individual larger polyps (solitary corals). The polyps live in symbiosis with certain photosynthetic protozoa ( zooxanthellae ) , by which they are supported in calcium separation: the protozoa consume CO 2 and thereby facilitate calcium precipitation.

Silicon dioxide

Diatoms ( diatoms ) precipitating silica from the water and form therefrom at normal temperature and normal pressure hydrous amorphous silicon dioxide (Skelettopal) from which they produce their delicate skeleton. This is very hard and at the same time tough, so that it offers optimal protection.

The proteins involved in the structure of this silicate armor can only be isolated by hydrofluoric acid, which is used to dissolve the skeletal opal. Some of the amino acids that make up the proteins do not belong to the “standard repertoire” of living nature, but have been significantly changed afterwards. The original amino acid sequence could be determined indirectly via the genetic information. Two types of proteins have been identified: The high molecular weight protein is apparently incorporated into the skeletal opal structure for reinforcement. The low molecular weight proteins (“silaffins”) are able to precipitate a solid with a complex nanostructure from ordinary silica within minutes.

Dead diatoms can form deposits of diatomaceous earth . Due to its large inner surface, diatomite is an important technical aid, for example for cleaning beverages in the food industry and for producing dynamite from nitroglycerine.

The flora also has a large turnover in silicon dioxide. It is known that rice plants use silicon dioxide to stabilize their stems, improve light absorption and seal the leaves against water loss through evaporation.


  • At the University of Kassel the optical properties of the silica structures of diatoms are investigated.

Hydroxyapatite (bone)

The bones of vertebrates (vertebrates) consist of about 65% inorganic components, mainly hydroxyapatite , a calcium phosphate with the formula Ca 5 [OH | (PO 4 ) 3 ] and about 35% organic components, mainly collagen . Collagen is a structural protein with very high tensile strength. In addition, there are proteins and fats as well as water in fresh bones. The hydroxyapatite causes the compressive strength and rigidity, the collagen the tensile strength of the bones.

Dinosaur National Monument, USA, guided tour on the exhibition wall

Hydroxyapatite can be produced in certain cells, the osteoblasts , from phosphate and calcium ions. For this purpose, phosphate ions are first released in a collagen matrix made of organic phosphates until the solubility product for calcium phosphate is exceeded. Collagen acts as a crystal nucleus and hydroxyapatite crystallizes out. The high strength is due to the fact that the crystallites of the hydroxyapatite align themselves in lines of tension preferentially after compressive and tensile stress and thereby form a strut-like structure. This architecture of bone structure can be traced back to the dinosaurs using fossil material.

The bones of killed animals have been extremely valuable to humans for thousands of years: As a "composite material", bones were an important raw material for the manufacture of tools. The organic components provided bone glue and the inorganic components (e.g. as bone meal or bone ash ) a valuable phosphate fertilizer (until this type of application was banned because of the BSE problem).

Bones take a relatively long time to decompose after the death of a vertebrate. Therefore, there is a higher probability for them to be passed down in fossil form than for the soft tissues. Fossil bones are therefore an important “archive of life”. What man knows today about the evolution of vertebrates and thus also about his own development history, he owes primarily to the comparatively high fossil preservation capacity of bones and teeth. The diet, illnesses and the consequences of armed conflicts are "archived" in bones and teeth. In rare cases, remains of genetic material could still be detected in fossil bones. An impressive example of the archival function of bones can be seen in the Dinosaur National Monument in the USA.

Hydroxyapatite and other apatites also arise under certain biochemical conditions in the soil (entire deposits are created in this way) and are often indistinguishable from bone hydroxyapatite mineralogically and morphologically. The decisive factor is the microenvironment and the resulting chemical solutions (see Schmittner and Giresse) created by clay particles, bacteria (containing about 5% P) and other micro-beings (monosaccharides produced by algae for the explosive multiplication of bacteria). The concentration ratio of Ca to P in the micro-solution determines the formation of hydroxyapatite or calcite. Flat hydroxyapatite crystals, 10 micrometers in size, can be produced within 3 to 5 days using high equal P and Ca concentrations. For another simple illustration: a double concentration of Ca to P results in calcite. In addition, our daily deposits on the teeth consist of up to 60% hydroxyapatite (formed in the presence of oxygen) and partly also calcite (but no oxygen in the "micro-world" here, as it is used up by oxygen-consuming bacteria), especially after eating sweet Food; However, these deposits are undesirable because they contain a myriad of bacteria and, as is well known, bacteria produce acids that in turn attack the tooth enamel and leave a "micro to millimeter crater landscape" on the tooth surface.
In other words, the purely chemical prerequisites for the formation of hydroxyapatite in the bones do not differ from those that are given when hydroxyapatite is deposited as a deposit on the teeth, or those that favor the formation of hydroxyapatite in rocks.


Tooth enamel consists primarily of hydroxyapatite. The hardness of the tooth enamel is primarily due to the fact that it consists predominantly (approx. 95 percent) of inorganic material. With fluoride-containing preparations (medicines, dental care products) it is possible to partially replace OH groups in the hydroxyapatite with fluoride ions and thus partially convert the hydroxyapatite into fluorapatite. This is more resistant to acids and therefore has a better protective function against tooth decay.

Current research


The priority program of the German Research Foundation (DFG) "Principles of Biomineralization", which has been running since the middle of 2003 , under the leadership of the University of Hanover, deals with fundamental issues on the subject of "biological composites" with the inorganic components calcium carbonate, silicon dioxide and apatite. The Max Planck Institute for Metals Research in Stuttgart has a focus on “Bio-inspired synthesis of ceramic materials”. The architecture of the bone structure can be traced back to the dinosaurs using fossil material , a topic that is worked on at GKSS , Geesthacht, with the most modern instrumental equipment. Research with predominantly medical objectives has been carried out in Dresden for around 15 years.

Only a few topics can be highlighted from the worldwide activities on the subject of "biomineralization":

DNA is ideal as a construction material on the nanometer scale. This is made possible by the fact that DNA sequences can be programmed so that they couple very specifically to other molecules, which in turn interact with inorganic particles. Since different DNA sequences can be constructed in such a way that they attach to one another, there are almost unlimited possible combinations.

A research group at New York University uses genetically modified bacteria of the genus Escherichia coli to synthesize a peptide that is able to precipitate gold particles from a solution of gold (III) chloride and to adhere to the gold surface. The amino acid sequence glutamine / alanine / threonine is assumed to be the active sites of the peptide . This simple system has so far only been used for basic research.

At the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts, bacteriophages (M13 viruses) are grown, which are coated with metallic cobalt in a solution of a cobalt salt . When the cobalt was oxidized, the scientists obtained wires made of cobalt oxide 6 nanometers thick and 900 nanometers long. In an orienting test, they were able to prove that this material is suitable as a component of a lithium-ion battery.

Another research focus is the following problem: About half of the CO 2 that is produced when fossil fuels are burned and that contributes to global warming is absorbed by the oceans. This threatens to acidify the oceans , with the result that the formation of calcareous structures during biomineralization is made more difficult.

Biomimetic crystallization

In materials science, biomineralization - called “biomimetic mineralization” in the chemist's laboratory - is playing an increasingly important role. Intensive research is carried out into the laws according to which self-organization takes place, which leads to composite materials consisting of organic and inorganic components being created from the starting substances. Peptides play a key role in this.

Certain peptides are also suitable for generating purely inorganic crystals. For example, a peptide has been found that enables the formation of powellite (a calcium molybdate with the formula CaMoO 4 ) in aqueous solution. The technical production of this mineral, which z. B. is used as a phosphor in LEDs, requires temperatures of 500 to 1000 ° C.


  • M. Groß: Molecular recognition between biomolecules and crystals . Spectrum of Science, February 1995, 25-26
  • M. Groß: The secret of the nano-pebbles . Spectrum of Science, January 2000, 24-26
  • M. Groß: Materials at the Interface of biology and chemistry . News from Chemistry 53, November 2005, 1135–1138
  • NN: Dinosaur bones: Model for new structural materials . GKSS-Forschungszentrum Geesthacht GmbH, annual report 2003/2004, 33–35
  • SC Doney: The Ocean Goes Sour , Spectrum of Science, Jun 2006, pp. 62–69
  • K.-E. Schmittner, P. Giresse, 1999. Micro-environmental controls on biomineralization: superficial processes of apatite and calcite precipitation in Quaternary soils, Roussillon, France. Sedimentology 46/3: 463-476.
  • H. Cölfen: Biomineralization from the test tube , Nachrichten aus der Chemie 56 (January 2008), 23-28
  • Biomineralization. From Biology to Biotechnology and Medical Application (Wiley-Vch), Edmund Baeuerlein (Ed.), 2001, Wiley & Sons. ISBN 3-527-29987-4
  • Handbook of Biomineralization. 3 vols, Edmund Baeuerlein (Ed.), Peter Behrens (Ed.), Matthias Epple (Ed.), 2007, Wiley & Sons, ISBN 3-527-31641-8
  • GC Schwartze: Micro-range analysis of marine biomineralization products: Copepods of the Southern Ocean and the North Sea . Grin Verlag, Munich, 2011, ISBN 978-3-640-85438-7

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