Biologically Controlled Mineralization in Prokaryotes

As stated in an Chapter 4, prokaryotes of both Domains or Superkingdoms, the Bacteria and the Archaea, mediate the formation of a large number of diverse minerals. They are known to do this either through biologically induced mineralization (BIM) (Lowenstam 1981) (the subject of Chapter 4 in this volume; Frankel and Bazylinski 2003) or biologically controlled mineralization (BCM). The latter has also been referred to as organic matrix-mediated mineralization (Lowenstam 1981) and boundary-organized biomineralization (Mann 1986). There are several important differences between BIM and BCM that will be discussed in detail in this chapter, most notably those dealing with aspects of the mineral crystals and the biomineralization process (see also Weiner and Dove 2003). However, there is another significant difference between the two modes of biomineralization and this is the aspect of functionality. Generally, in BIM there is no function to the biomineralized particles except, perhaps, as a solid substrate for attachment in the case of bacteria or as a form of protection against certain environmental conditions or attack from predators. However, it is easier to recognize the primary function of bone or shells produced by molluscs; two well-characterized examples of BCM by higher organisms. Functionality should always be examined when dealing with examples of biomineralization particularly in situations where the mineral product displays some qualities of both BIM and BCM.