Chem 8157

In today's seminar, Daniel Bond described his work with electron-producing anaerobic bacteria. These organisms contain enzymatic pathways to oxidize molecules such as acetate to produce ATP and generate a net flow of electrons (current) as a byproduct. Dr. Bond studies these bacteria with several analytical techniques. He cultures bacteria in special sealed electrode chambers (in an oxygen-free environment) containing a graphite electrode. Scanning electron microscopy (SEM) has been used to study the smoothness of these electrodes- this is a property that affects how close the bacteria can come to the surface (an important parameter for electron transfer). The bacteria accumulate on the electrode as they multiply - Dr. Bond's group has used confocal fluorescence microscopy to characterize the thickness of the layer of bacteria that accumulate on this electrode. Briefly, this technique uses a set of optics to remove out-of-plane fluorescene produced by laser-induced excitation of a sample so that only one focal plane of light is allowed to reach the detector.

Dr. Bond's group uses electrochemical techniques to study the properties of electron transfer from the bacteria to the electrode. In the seminar today, he focused on the results obtained from cyclic voltammetry, a technique in which potential is scanned and current is measured. Data obtained from this technique can be manipulated to provide mechanistic rate constants like k_cat and estimates for redox potentials of the enzymatic reactions occurring in the bacteria.

I just wanted to comment on Dr. Bond's presentation. I thought it was an amazing concept that you did not have to add a catalyst to lower the activation energy of an enzymatic reaction. Instead, he commented on adding a burst of energy, like a pulse, to make the electrons jump the energy barrier. His discussion on different enzymes and how they could be mapped on a grid and thereby link enzymes and how they react to a single substrate was also very interesting.