Light my wire: correspondence
with Ed 072205
Re the light activated biowire My one comment is that this basically is an energy conversion problem, if you want to help drive current with light. What happens in nature with geobacter is it can to oxidize acetate anaerobically, and reduce a variety of terminal electron acceptors, like sulfate, or graphite electrodes that span a redox gradient - maybe using pili as a physical conduit sometimes. Anaerobic oxidation of acetate is what ultimately drives the current, and where the electrons come from. How to couple this to light ?
I haven't thought this through entirely, but here's my off the cuff on the PR biowire idea. The two basics in cellular energetics are energy and reducing power. What we know right now, is that the light-driven proton pumping works with these rhodopsins in E coli. That gets you to a light-activated proton motive force - so far so good. Now, if you're going to drive electron transfer from that, you have to somehow convert the proton motive force into reducing potential. Not impossible - you can drive otherwise thermodynamically unfavorable redox rxns for example with that chemiosmotic potential (but you still have to grab your electrons from somewhere). Some bugs do this kind of thing, basically running respiratory chain in backwards, so called "reverse electron transport" to generate NADH from exogenous reductants. But the light -> reducing power -> current while attractive, isnt straightforward to my mind. It *is* a cool bioengineering problem thats probably tractable, but maybe not ready for prime time in a course...
Re: cloning new PRs The cloning of PRs would be an easier project, and basically you can either screen libraries with probes, or if you are cloning into a high copy # vector, by allowing it to express in media containing retinal - this produces colored colonies. But you have to screen beacoup colonies... This would be a tractable excercise, because one could characterize the clones then in a variety of ways.