Bacterial biomineralization: where to from here?

It is widely accepted that bacteria bind metals and form minerals, but where did this understanding come from? The answer is simple, Terry Beveridge. His pioneering research in the 1970s, as a PhD student at the University of Western Ontario under the supervision of Drs Robert Murray and William Fyfe, demonstrated that the outer surfaces of the common soil bacterium, Bacillus subtilis, could bind so much metal that they formed dense aggregates (e.g. Beveridge & Murray, 1976). Transition metals, in particular, imparted such strong electron-scattering power into the cell wall that some of them have subsequently been used as contrasting agents for electron microscopy (Beveridge, 1978). Indeed, many of the advances made on bacterial ultrastructure over the past three decades were made possible by metal staining and visualization of thin sections under the transmission electron microscope (TEM). From this work, another pivotal paper followed. In it, Terry used a variety of chemical treatments to modify or remove electronegative and/or electropositive groups within the cell wall of B. subtilis, and in doing so, showed that it was the anionic carboxyl groups in Gram-positive cells that contributed most to metal binding (Beveridge & Murray, 1980). By contrast, subsequent research with Gram-negative cells, such as Escherichia coli, showed that phosphate groups in the outer membrane were the main metal-binding groups (Ferris & Beveridge, 1986).