It’s only my first attempt at anything like this, so constructive comments are welcome…
(Hopefully you can see the embedded audio player here…)For those of you just tuning in, this is a 90-second explanation of Why Microbial Fuel Cells work. A longer (though still simple) explanation can be found at a slightly older post here.[Update: this was featured in the November 6, 2007 broadcast! Hooray, I can now claim to be an international “radio personality”!]Presuming hosting this file doesn’t kill my bandwidth, I’ll leave it up here. BelowAbove, you should see an embedded flash player (assuming you have Macromedia® Flash® player installed) which you should be able to click on to start the audio. I’ll also place a direct download link below. It should be noted that like everything else on this blog (unless otherwise specified), this audio is also available under the Creative Commons non-commercial/attribution/share-alike license, so as long as you have no problem with the terms of that license you are welcome to copy, redistribute, put up on bittorrent, host a public performance, turn into an interpretative dance art project, or whatever else you might want to do with it so long as you give me credit for it, don’t use it for commercial purposes, and distribute any derivative works of it under the same terms.
You can download the audio directly from here – right-click on the link and select “save link as…”. Ogg Vorbis format available on request…
That’s just awesome. Anything that can make your brother-in-law actually stop what he’s doing and ask “What the f*** was that??” has my thumbs up.
But seriously. Do more. Lots more. You’re fun to listen to when you get into “weird science” mode. 😉
I just caught your explanation of microbial fuel cells on an old episode of TWIS. It was so brill I actually rewound it twice to listen again and catch your website. (Your voice is so deep I could barely make it out…or possibly I should turn off the ultramegabass.)
In any case: Awesome job.
And a question: Could a person make a microbial fuel cell at home? (Just for fun–I realize this isn’t yet up to powering my house.) Like, what are these special bacteria (if such they be) that let their electrons go over a wire to oxygen elsewhere?
Thanks for the compliment, not to mention for taking the trouble to track down my blog to comment!
Although my “recording” voice is a bit deep, I think the version on the TWIS podcast was deepened slightly further – this being my first attempt at this kind of thing, I was somewhat rushing to make sure I could get the whole explanation into the allotted 90 seconds – as I recall it came in at about 75 seconds. I think they stretched the recording out to the full 90 seconds to slow down what I was saying in hopes of making it easier to follow, but doing so dropped the pitch a bit, too.
To be honest, I haven’t yet directly tried doing it myself, though I have an active 1-gallon jug of Gunnison Bay water that I want to try it on at some point.
Hypothetically, it should be really easy to make one. The bacteria that can breathe through electrodes do one of two different things. They can excrete some kind of “shuttle” molecule that can carry electrons out of the bacteria, give them up at the electrodes, and then get back into the bacteria for more – apparently at least some species of Geothrix bacteria do this[1]. In the yeast-based fuel cell demonstration, the methylene blue that’s added works exactly this way, except of course the yeast aren’t making the dye themselves. The other way is to secrete biological “nano-wires” made with strings of iron-containing molecules that can pass the electrons along directly to the electrodes. The most famous bacteria that do this seem to be Geobacter sulfurreducens and Shewanella oneidensis, but there seem to be many others that can as well.
Basically, if you set up some electrodes in an environment with active bacteria, it seems likely that some will be able to “breathe” through the electrodes, and those bacteria will tend to grow faster because of it. Papers I’ve read seem to suggest that it takes anywhere from a couple of days to a couple of weeks to get up to full activity, but it seems to happen automatically.[2] Right now, it seems like the only environments that are really well examined are wastewater and ocean sediments. I’d like to do some experimentation in other environments and see what other kinds of bacteria might be able to do this.
[1]Bond DR, Lovley DR: “Evidence for Involvement of an Electron Shuttle in Electricity Generation by Geothrix fermentans”; APPLIED AND ENVIRONMENTAL MICROBIOLOGY;Apr. 2005(71:4);p. 2186–2189
[2]Rabaey K, Boon N, Siciliano SD,Verhaege M,Verstraete W:”Biofuel Cells Select for Microbial Consortia That Self-Mediate Electron Transfer” APPLIED AND ENVIRONMENTAL MICROBIOLOGY;Sept. 2004(70:9), p. 5373–5382
Basically, if you set up some electrodes in an environment with active bacteria, it seems likely that some will be able to “breathe” through the electrodes, and those bacteria will tend to grow faster because of it.
Whoa whoa whoa. I know what I’m trying this weekend!
Wait…I can’t do that one with yeast….they’ll just make alcohol. I don’t know the first thing about biochem. Well, maybe I know the first thing, but I definitely don’t know the second.
But I can probably dig up some graphite rods, wire and bacteria.
The alcohol won’t be a problem here – the alcohol production only happens when the yeast can’t “breathe”. If they have oxygen (or, hypothetically, an electrode and a shuttle molecule) they should oxidize everything all the way down to carbon dioxide and water.
Actually, since yeast culture for brewing and other food-type uses is something I want to play with, I’ve been wondering if I might incorporate some electricity and methylene blue action into the culturing process, just to see what kind of effect it has on the mutation rate and health of the culture.