Calcium carbonates: Induced biomineralization vs. controlled macromorphology?

Abstract

<p><strong>Abstract.</strong> Biomineralization of (magnesium) calcite and vaterite by bacterial isolates has been known for quite some time. However, the extracellular precipitation hardly has been linked to different macro-mophologies of the minerals that are observed. Here, isolates from limestone associated groundwater, rock and soil were shown to form calcite; magnesium calcite or vaterite was also present. More than 92 % of isolates indeed could form carbonates, while aboitic controls failed in mineral formation. The crystal morphologies varied, including rhombohedra, prisms and pyramid-like macro-morphologies. Using different conditions like varying temperature, pH or media components, but also co-cultivation to test for collaborative effects of sympatriotic bacteria, were used to differentiate mechanisms of calcium carbonates formation. Single crystallites were cemented with bacterial cells; these may have served as nucleation sites by providing a basic pH at short distance from the cells. A calculation of potential calcite formation of up to 2 g per liter of solution could link the microbial activity to geological processes.</p>