FROM OBSERVATION OF FORM TO MOLECULAR SCALE MECHANISMS: BIOMINERALIZATION RESEARCH PAST, PRESENT, AND FUTURE

Studies of biogenic minerals enjoy a rich history that largely began in the 1950's as separate enterprises in the medical and geological communities. While medical groups sought to understand skeletal diseases, Lowenstam and Urey focused on developing an isotope-based chemical proxy for temperature that could be applied to ancient environments. Their work marked the onset of quantitative efforts to interpret signatures contained in biogenic minerals. In finding that few biominerals are deposited in isotopic equilibrium, they were the first to recognize physiological effects, later known as “vital effects”— a forefront topic in paleoclimate research.

The advent of SEM disclosed structural details of many biominerals, but provided limited information about relationships between intracellular macromolecules and biomineral morphology. Stereochemical relationships between modifier and mineral were inferred primarily from macroscopic growth experiments. Limited rigorous and quantitative analysis within established formalisms of nucleation and growth were pursued, in part because these systems were recognized as very complex.

Because the formation of structural components in organisms finds its roots in mechanisms taking place at the nanoscale, the field is presently moving rapidly forward with insights from new high-resolution characterization technologies. A fundamental shift is occurring with the realization that biogenic calcite or aragonite may rarely form by the processes envisioned within classical models of crystal growth from solution— rather, calcification (and silicification) begins with amorphous precursors that experience temporal changes en route to final products. The importance of such nucleation pathways, dominance of kinetic controls over thermodynamic drivers, and the need for computational approaches to understanding stereochemical relationships have taken center stage. Also far-reaching is an emerging understanding of how growth dynamics control minor and trace element contents in minerals—biological or not. Over the next 15 years, these and other studies promise a science-based understanding of how genetics, biomolecules, and microenvironment influence the onset of mineralization, compositional signatures, and polymorph selection.