Understanding Interfacial Processes:....

Speaker:Dr. Megan Ferguson, Postdoctoral Fellow
Occidental College
Los Angeles, CA Understanding interfacial processes: TiO2-photocatalyzed As(III) oxidation and Bacterial predation by Bdellovibrio bacteriovorusAbstract
The U.S. drinking water standard has recently been revised from 50 ƒÝg L-1 to 10 ƒÝg L-1, thus requiring thousands of water distribution facilities to implement new As removal procedures. However, most As removal technologies treat As(V) much more effectively than As(III), so a pre-oxidation step is recommended for source waters containing As(III) at significant concentrations. The photocatalyzed oxidation of As(III) on titanium dioxide (TiO2) has been critically evaluated as a potential technology to achieve pre-oxidation. Mechanistic studies conducted with batch slurries demonstrated that the extent of As(III) sorption to TiO2 dictates the order of the photooxidation reaction and that photogenerated superoxide plays a major role in this reaction. Experiments with fixed-bed, flow-through reactors did not suffer from catalyst poisoning or severe mass transport limitations. The UV requirement for this photooxidation of micromolar levels of As(III) was sufficiently small that both a 365 nm handheld lamp and natural sunlight were effective. Based on these findings, TiO2-photocatalyzed As(III) oxidation could be a viable pre-oxidation technology for certain small water distribution facilities.
The predation of E. coli by Bdellovibrio bacteriovorus is a very different example of interactions at an interface. B. bacteriovorus burrows into the periplasm of other gram-negative bacteria, where it feeds on the prey cell cytoplasm and ultimately divides, lyses the prey cell, and moves on to new prey. Understanding these microbial interactions could contribute to many potential applications in which B. bacteriovorus is used to reduce unwanted bacteria in agriculture, medicine, and industry. In these studies, atomic force microscopy (AFM) was used in contact, tapping, and force modes to characterize the cell surface properties over the course of B. bacteriovorus infection. Force curves taken in buffer solution show that the adhesive force between a cell and the AFM tip increases significantly after an E. coli cell has been infected.

Location: Kaprielian Hall (KAP) - rielian Hall, Room 203

Audiences: Everyone Is Invited

Contact: Evangeline Reyes