Natural Antibacterial Clay Mineralogy ~ Medical Geology ~

1. Clélia Tommi & Dr. Lynda Williams School of Earth & Space Exploration Natural Antibacterial Clay Mineralogy~ Medical Geology ~

2. Why do Antibacterial Clay Research? - Overuse of antibiotics around the world - Proliferation of antimicrobial resistance strains • - Identification of new antibacterial agents - What makes a natural clay antibacterial? Buruli 1 Staphylococcus MRSA

3. First, let’s define what are clays? • Common misconceptions between • CLAY SIZE & CLAY MINERALOGY • Clays are a fine grained particle • size less than 2 µm diameter • The mineralogy of clay • deposits is variable but mostly • composed of phyllosilicate • minerals.

4. What makes the structure of clays so important? TETRAHEDRAL OCTAHEDRAL TETRAHEDRAL Interlayer CATIONS TETRAHEDRAL OCTAHEDRAL TETRAHEDRAL - Interlayer cations can exchange when hydrated

5. What makes the structure of clays so important?

6. Electron Microscopy of Clay Minerals

7. How does clay interact with the bacteria? • - Metals have been used as antimicrobial agents • since antiquity • - Studies indicate that different metals cause discrete • and distinct types of cell damage http://www.nature.com/nrmicro/journal/v11/n6/full/nrmicro3028.html

8. Experimental Methods Testing clays for their antibacterial properties Rhodes Clays, North Carolina OMT Clays, Oregon Greeney’s Clays, New York Walker’s Clays, Nevada In Vitro Antibacterial Testing - Bacterial Plate Counting - Disk Diffusion Mineral Analysis • X-Ray Diffraction • RockJock Analysis

9. In Vitro Antibacterial Susceptibility Testing - Bacterial Plate Counts Summary of bar graph showing E.coli growth in sample incubated with clay minerals

10. In Vitro Antibacterial Susceptibility Testing - Disk Diffusion Petri dishes showing zone of inhibition - 0 mm Rhodes - 0 mm Greeney - 24 mm OMT - 50 mm Walker Petri dishes showing the zone of inhibition for the OMT clay (24 mm), compared to the Rhodes clay that is not antibacterial

11. XRD Mineral Analysis • Random powder X-Ray Diffraction • pattern of the Greeney Clays

12. XRD Mineral Analysis • Random powder X-Ray Diffraction pattern of the Walker Clay

13. Conclusions - Antibacterial testing showed that the Rhodes and the Greeney clay are not antibacterial, but the OMT and Walker clay are. - XRD shows the presence of goethite and anhydrite in the Rhodes and Greeney clay, suggesting oxidation. Other minerals are igneous and metamorphic assemblages. - The antibacterial clays (OMT and Walker) are hydrothermally altered deposits that contain reduced metals (e.g., pyrite). • - The oxidation state (Eh) and acidity (pH) of the clays equilibrated with water is important to the antibacterial effect.

14. Questions? - Disk Diffusion Thank you!