Biominerals coccoliths

Meldrum, 2002), the elaborately shaped spicules in ascidians, and finely the sculpted coccolith shells in coccolithophores (Mann, 2001). For silica structure, the diatoms produce the most exquisite siliceous cell wall (Sumper and Brunner, 2006). Also the calcium phosphate in bone shows a highly regulated organization and arrangement. Interestingly, avians have two main biomineralization systems, one produces calcium carbonate for egg shell and the other produces calcium phosphate for bone (Bauerlein, 2000 Mann, 2001). 

The first candidate is an inorganic mineral formed either by chemical processes or through some form of biomineralization. The latter development may have been an evolutionary response by the cellular material to improve on its coincidental use of an existing mineral structure. The previous examples all presume a cell, or cell model, with a flexible outer membrane composed of a water impermeable material such as a lipid or phospholipid. However, as mentioned at the start of this chapter it is possible to form capsules from materials that are rigid solids. In Nature the best examples of these are algae that form plates of metal carbonates, coccoliths, and... 

The use of biomineralization to compartmentalize materials occurs on many scales from the coccolith-forming algae discussed below to the shells of birds and reptiles. It has also been demonstrated by Martel and Young that combinations of calcium salts and proteins generate hollow calcium rich shells which bear very close similarities to purported remains of nanobacteria [24],... 

Lowenstam and Weiner (1989, pp. 8-11, table 2.1) clearly show that carbonates dominate in biomineralization. They even occur in plants and fungi. The volume percent of limestone and marbles is well documented from the Precambrian to the present. Whether these rocks are inorganic precipitates or festooned with fossils, many of the living creatures had biomineralized with calcium carbonate, is usually clear. Indeed, some strata are composed entirely of calcium carbonate shells. We present examples of carbonate mineral deposition in cyanobacteria, corals, coccoliths, foraminifera, mollusks, echinoids, and the arthropods. 

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