Bacterial Nanowires

Nanowires- with high conductivity

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Most of us who work in biochemical engineering know that nature has supplied us with a variety of microbes that provide great starting grounds from which we can develop the specialized strains we need.  In my case, that meant finding two strains that could degrade ammonia to innocuous gases- and with a little manipulation, a viable product was soon available.   We employed the same process to eradicate aromatic hydrocarbons and,m then again, for some specialized mining situations.   (The first set of microbes where I used this process involved finding the right bunch of bugs in nature for the inoculum to  degrade honest-to-goodness solid waste to methane near Deer Island and the Boston Common- for one of my theses.)  I also reported that Drs. Lewis and Epstein used the same ideas for their new antibiotic development.

Well, this concept is still viable, in these days of CRISPR/Cas9 genetic constructions.  Drs. Y Tan, RY Adhikari, NS Malvankar, S Pi, JE Ward, TL Woodard, KP Nevin, Q Xia, MT Tuominen, and DR Lovley (all from the University of Massachusetts) published the results from their studies. The article, Synthetic Protein Nanowires with High Conductivity, was just published in Nanotechnology.  Starting with a strain of Geobacter (isolated near DC in the Potomac River- pretty far from Massachusetts), they capitalized on the microbes ability to derive energy from iron oxide. Actually, the microbes transfer electrons through tiny filaments.  And, from that start, this multidisciplinary team were able to “convince” the microbes to product tiny filaments, basically- nanowires.

Bacterial Nanowires

The problem is that while Geobacter sulfurreducens grows in nature, those filaments it produces don’t carry any appreciable current. Hmm.  Why else do we have genetic engineering and manipulation?  The researchers had the microbes producing filaments containing tryptophan.  (No, this really doesn’t put you to sleep- but it IS a great vehicle for electron transfer.  Especially for those ranging on the size nanometers (that’s a billionth of a meter.)

Nanowires- Geobacter sulfurreducens

How successful was this change?  Oh, not much.  Just able to boost electrical conductivity by nearly 2000X- in filaments 60,000 times thinner than the hair on your head.  And, despite its size and current carrying capability, these filaments seem pretty durable. And, they can be embedded in resins (plastics)- even though they are pretty short.

Given that length, these conducting filaments would be useful in medical sensors, especially since they are very sensitive to pH changes.  Or, the filaments could function as transistors (you know, the building block in a microchip) or capacitors (temporary batteries).

I can hardly wait to see how this scale-up moves along.

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