Interactions of Biomolecules and Bacteria with Titanium at the Mineral Microbe Frontier

Temple University, Philadelphia PA

Investigators

Abstract

In this project funded by the Environmental Chemical Sciences Program of the Chemistry Division, Professor Ann Valentine of Temple University is studying how biological molecules and whole microorganisms bind to and dissolve titanium oxide surfaces. Titanium is one of the most abundant elements on earth, but its role in biology is, at best, obscure. Titanium oxides are the most prevalent form of titanium in the environment, but they are normally very inert. Iron-scavenging biomolecules unlock an activity that is otherwise disfavored: the release of large quantities of titanium ions into solution. This research is revealing the role of titanium in biology and, conversely, how biology impacts the environmental chemistry of titanium. This project focuses on the interactions of iron-scavenging siderophores and bacteria with titanium dioxide surfaces, and on the chemical consequences of those interactions. The "siderophore"-mediated mobilization of titanium ions from titanium dioxide is being characterized quantitatively. The oxide surface and materials properties before, after, and during dissolution is being probed by using Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy as well as microscopy and related techniques. Microbe/oxide and biomolecule/oxide interactions are being studied by using the bacterium Rhodococcus ruber GIN-1, which adheres avidly to titanium dioxide and incorporates titanium into its biomass. Titanium dioxide surface binding proteins are being identified and characterized, and their abundance and properties correlated to whole-organism phenomena. Titanium uptake is being quantified and intracellular titanium binding molecules isolated. Rhodocuccus ruber GIN-1 siderophores are being isolated and characterized. Research activities are integrated with a program to improve teaching and learning in introductory undergraduate chemistry at Temple University. Environmental bioinorganic chemistry is featured in chemistry outreach efforts. The broader impacts of this work include potential technological benefits from new strategies for anchoring organic molecules to titanium dioxide surfaces, and from the identification of the first native titanium-biomolecule complex and potentially a titanium enzyme.