Abstract:

Biosilica, more specifically hydrated amorphous silica, often referred to as opal, is the second most abundant mineral
type  formed by organisms, with only  the carbonate minerals exceeding  it  in abundance and distribution. As  the predominant
contributor  to biosilica  in  the oceans, diatoms are known  for  the  intricate geometries and spectacular patterns of  their silica-
based cell walls. Biochemical studies demonstrate that diatom biosilica is a composite material containing several general organic
components in addition to inorganic silica, such as polysaccharides, long-chain polyamines and zwitterionic proteins. Functional
studies on these organic components indicate that they play a crucial role in guiding silica precipitation as well as in the formation
of species-specific nanopatterns. This article gives an overview of current knowledge on the function of above-mentioned organic
and biological molecules  in biosilicification. Moreover, some studies of biomimetic mineralization using model organic additives
and in vitro experiments using molecules extracted from organisms are also involved. An insight into the silicification mechanisms
in diatoms will link the global cycles for Si and C mechanistically, whereas identification and classification of the components in
diatoms may assist us in deeper understanding of material sources of petroleum and the evolutionary development of diatoms.

Key words:  diatom, biosilicification, biomineralization-associated molecules, organic matrix-mineral interaction