Biopolymers from a Bacterial Extracellular Matrix Affect the Morphology and Structure of Calcium Carbonate Crystals

Abstract

Biomineralization is a mineral precipitation process occurring in the presence of organic molecules and used by various organisms to serve a structural and/or a functional role. Many biomineralization processes occur in the presence of extracellular matrices that are composed of proteins and polysaccharides. Recently, there is growing evidence that bacterial biofilms induce CaCO3 mineralization and that this process may be related with their extracellular matrix (ECM). In this study we explore, in vitro, the effect of two bacterial ECM proteins, TasA and TapA, and an exopolysaccharide, EPS, on calcium carbonate crystallization. We have found that all the three biopolymers induce the formation of complex CaCO3 structures. The crystals formed in the presence of the EPS are very diverse in morphology and they are either calcite or vaterite in structure. However, more uniformly sized calcite crystals are formed in the presence of the proteins; these crystals are composed of single crystalline domains that ass...