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| Shewanella bacteria growing on culture plates |
During
my PhD I worked with a micro-organism called Shewanella oneidensis MR-1.
It's a rod-shaped bacterium that was first isolated in 1988 from the sediments
of Lake Oneida (New York State). It's a model organism for a process called extracellular
electron transport, where electrons are transferred from the inside to
the outside of the bacterium during respiration (almost like a flow of
electricity coming out of the bacterium!). The process starts when electrons
are released from the breakdown of food by the bacterium. The electrons are
then transferred across the cell membrane to external molecules/metals via
iron-containing proteins called cytochromes. Shewanella produce loads of
cytochromes so have distinctive red-coloured cell pellets (compared to E.
coli which typically have white-coloured cell pellets).
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| Shewanella growing in a liquid nutrient-rich broth |
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| Shewanella red pellets after centifugation! |
The bacterium is also what's called a facultative anaerobe meaning
it can survive in environments both with and without oxygen. The highly
versatile nature of the microbe makes it relatively quick and easy to grow and
study in a laboratory. On the downside, my research colleagues tell me that
it can be much harder to genetically modify compared to something
like E. coli (fortunately I didn't have to do much genetic modification
work in my PhD though!).
The process of extracellular electron transport can be exploited using a device
called a microbial fuel cell which uses electrodes to capture the
electricity generated by Shewanella. Small, hand-held devices can power
things like LEDs, digital timers and calculators. The bacterium is therefore an
important model organism because it represents a relatively sustainable way to
produce electricity, particularly because it can be grown using a wide variety
of food sources. Current research aims to further understand the movement of
electrons within the bacterium and explore ways to make Shewanella even
better electricity-producers.
Further reading
If you are interested in learning more about Shewanella you can read a recent review article published by the Royal Society here
Further viewing #ScienceFromHome
Sam has made two #ScienceFromHome videos for more information about bacteria!
The first one is about electric bacteria click here to view! and the second one is about Shewanella oneidensis MR-1 which you can find our more about and view here
To see what Sam get's up to you can link up on Linkedin or follow him on Twitter!
LinkedIn: https://www.linkedin.com/in/samrowe1/
Twitter: @samfrowe
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