Unusual Crystal Formation in Organisms - Exceptions that Confirm Biomineralization Rules

Biomineralization is a complex combination of biochemical and physiological processes, depending on endogenous activity of an organism and the exogenous environmental influence. In marine organisms (bacteria, calcareous algae, molluscs, crustaceans, fish and mammals) biomineralization starts at early stages of development and continues during the entire life. These processes take place in different tissues, shells and skeletons, and are manifested in calcification, decalcification and in polymorph transitions of calcium carbonate in particular shell or skeleton layers (Lowenstam, 1981; McConnaughey, 1989). Biomineralization processes depend on a number of conditions of which the main ones, that influence the type and structure of the biomineral, are the following: supersaturation of the medium with calcium and other ions, the nature of the critical nucleus, characteristics of the organic matrix, promotors and inhibitors of phase transitions, environmental temperature, salinity concentration and pH ranges (Wilbur & Saleuddin, 1983; Addadi & Weiner, 1992; Mann, 1991, 2001; Bauerlein, 2004; Veis, 2008). The research related to the biomineralization processes is interdisciplinary and the main aim of the present review is to express and interpret results obtained by different methods and approaches. In this review we address three major topics. First, we turn back to the period before the modern biomineralization theory, which presents several innovative hypotheses and proposes mechanisms fundamental in understanding crystal formation in the living organisms. These advanced ideas were randomly or deliberately neglected and minimized in recent biomineralization literature, and they deserve attention.