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

Temple University, Philadelphia PA

Investigators

Abstract

This award is funded by the Environmental Chemical Sciences Program in the Division of Chemistry. Professor Ann M. Valentine of Temple University is supported to explore the interaction of titanium oxide surfaces with metal-scavenging biomolecules and/or microorganisms. Titanium is very abundant both in the environment and in organisms, and increasingly used in consumer products and industrial applications. Titanium is not widely appreciated as a bioactive element as it has a reputation for extreme inertness and insolubility in water. This research examines the ability of titanium dioxide to stick to (adhere) and release from well-characterized biomolecules and from a bacterium. Iron-scavenging biomolecules bind titanium especially tightly and keep it soluble and stable. They can also cause the release of large quantities of titanium ions into solution. This research sheds light on the impact of microorganisms on the environmental chemistry of titanium and reveals the biological role of titanium. The research is integrated with a new outreach program for rising high school juniors called Philadelphia Environmental Chemistry Explorations (PECE). Environmental bioinorganic chemistry is used as a platform to broaden participation in science. This project focuses on the interactions of iron-scavenging siderophores and bacteria with titanium dioxide (TiO2) surfaces. This inquiry sits at the intersection of inorganic and bioinorganic chemistry, biogeochemistry, and materials and environmental chemistry. Siderophores bind strongly to TiO2, and some siderophores dissolve titanium ions from the metal oxide surface, significantly remodeling the mineral in the process. Electronic spectroscopy, elemental analysis, and mass spectrometry reveal metal ion concentrations and speciation in solution. The oxide surface and properties before, during, and after dissolution are being probed using Attenuated Total Reflectance-Fourier Transfer Infrared (ATR-FTIR) as well as microscopy and related techniques. The mutual interference of titanium and iron is a special focus. Microbe/oxide and biomolecule/oxide interactions are being studied using the bacterium Rhodococcus ruber GIN-1, which adheres to titanium dioxide and incorporates significant quantities of titanium into its biomass. Titanium dioxide surface binding proteins are being identified and characterized. Their abundance and properties are correlate to whole-organism phenomena. Titanium uptake is being quantified and intracellular titanium-binding molecules isolated. A research program is maintained that educates and trains undergraduates and graduate students at the interface of inorganic chemistry and biochemistry. Research activities are integrated with chemistry outreach and with a new program for rising high school juniors. This program uses environmental bioinorganic chemistry as a platform to broaden participation in science.