267 years ago, Ben Franklin flew his kite to demonstrate that lightning was electricity.  But, it really wasn’t of much use to us until some 130 years later. On the 4^th of September 1882, the Edison Illuminating Company began operating the first power plant (Pearl Street) with a network of copper wires.  (The problem is that our electric grid has not really progressed much beyond that mess of copper wires.)

Except that’s not quite true.  Because we had electric grids operating long before that.  This grid operated in salt marshes, muddy river bottoms, maybe even the ocean floor.  You see, microbes have been providing electricity for a long time.  We just haven’t harvested it for our own needs.

Just like I found the microbes I needed to convert honest-to-goodness-solid-waste (HGSW) to methane gas almost 5 decades ago, scientists are finding microbes to achieve certain tasks operating in our ecosphere.  Some 30 years ago, Drs. John Stolz and Derek Lovley (Duquesne University) isolated Geobacter metallireducens in the Potomac River.  Of course, they then scratched their heads and tried a variety of techniques to discern how they could induce the microbe to grow and reproduce in the lab.  Using carbon compounds and operating anaerobically (no oxygen; since there isn’t much at the bottom of the Potomac), that means instead of using oxygen as the electron sink, these microbes use iron oxide (rust), converting it to magnetite, for their reactions.

After a while, Dr. Lovley (now at UMass) was the only one to continue the study of the microbe.  (He has since found the microbes exist in underground oil.)  And, now, he knows that Geobacter has the ability to sense when there is nearby rust- and when it does, it sprouts a pilus  (hairlike growth) to create a grid, connecting to the needed electron sink.  And, electrons flow from the microbe down the pilus to the rust (the receptor).   (By the way, when Geobacter are hindered from producing and extruding pili, there is no conversion of rust to magnetite.)  Moreover, Geobacter can connect to other microbes (who need a flow of electrons) instead of pili and the rust deposit; some actually convert carbon dioxide to methane.

It’s not just Geobacter.  Dr. Lars Peter Nielsen (University of Aarhus) found microbes in the Bay of Aarhus (Denmark) that convert hydrogen sulfide (the rotten egg smelling compound).   The microbes produce ‘wires’ that grow vertically in the mud of the bay, reaching 2 inches in length.  This wire is actually single cells piled up on another (consider a stack of 1000s of dimes), with a protein sheath surrounding them- and that pile is what conducts electricity.  And, at the top of the stack- where there is oxygen, the microbes use the electrons from the bottom feeders (from the hydrogen sulfide reactions) to attach to oxygen, producing water.  He calls these ‘cable bacteria’.

So, it’s not surprising the Dr. B Barstow (Cornell) is trying to wire these microbes to solar panels.  As the sunlight hits the panel, a stream of electrons is generated. These will then flow along the microbial wires to convert sugar into fuel.  (These microbes are of the genus Shewanella.)

We won’t be running our offices or homes with such generated power any time soon- but it is an intriguing avenue of research.

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