Eating Electricity!!!
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| Fig. 1 Structure of mitochondria (1). |
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| Fig. 2 Simple diagram of ETC/OXPHOS pathway (2) |
In our Biochem 2 Metabolic Pathways course, we have recently
started to study the electron-transport chain/oxidative phosphorylation coupled
pathway that occurs within the cell’s mitochondria, specifically the inner
membrane (with the exception of cytochrome c
in the intermembrane space [IMS], of course), where the transfer of electrons
from the NADH and FADH2 reducing equivalents generated from previous
metabolic pathways—such as glycolysis, b-oxidation,
and the citric acid cycle—is coupled to the formation of the voltage/pH
gradient between the IMS and the mitochondrial matrix (see Figs. 1 & 2)1,2.
This pH gradient is then utilized so that the protons (H+)
travel through the ATP Synthase in a fashion akin to a turnstile that forces
the otherwise unfavorable formation of ATP from ADP and inorganic
phosphate. ATP is essentially the
primary energy currency the cell uses for other energetically unfavorable
cellular processes. In one of my
post-docs, I worked on a project that dealt with Complex III of the ETC. Many pathologies, including cardiomyopathies,
aging, parkinsonism, and so on1 are attributed to mitochondrial
respiratory chain defects, but that is fodder for other potential blog posts.
We spend much
of the semester discussing how the electrons are acquired via different
metabolic pathways’ redox reactions, transported as NADH and FADH2
into that inner sanctum of the mitochondrial matrix, and ultimately used to
reduce O2 into water while providing the means for the synthesis of
ATP. Bacteria, however, must utilize
other means of producing their energy currency.
Recently, researchers at Harvard University have discovered bacteria
that can actually use Fe from the environment as the source of electrons, along
with sunlight, for energy production.
That in of itself is not what is uber-fascinating to me. They must get these electrons iron ore,
right? (So they just grow on iron
deposits?) Well, in the lab, these
scientists have proven that the “bacterium Rhodopseudomonas
palustris can
use natural conductivity to pull electrons from minerals located deep in soil
and sediment while remaining at the surface, where they absorb the sunlight
needed to produce energy”3,4. Essentially, this
bacterium can use the natural minerals as a circuit to conduct the electrons
(i.e. ‘electricity’) back to itself where it can “eat” it to produce the energy
the organism needs to survive. How cool is
that?!?!? For a general article concerning
this process see the Science Daily link below (ref. 4), and for the original
journal article see ref. 3.
1. Zapico SC, Ubelaker
DH. mtDNA Mutations and Their Role in Aging, Diseases and Forensic Sciences. Aging
Dis. 2013;4(6):364-380. doi:10.14336/AD.2013.0400364.
2. Poling
Vaccine/Autism Case-Implications for ME/CFS Patients. Available at:
http://www.theoneclickgroup.co.uk/news.php?id=2428#newspost. Accessed March 11,
2014.
3. Bose
A, Gardel EJ, Vidoudez C, Parra EA, Girguis PR. Electron uptake by
iron-oxidizing phototrophic bacteria. Nat Commun. 2014;5.
doi:10.1038/ncomms4391.
4. Harvard University. (2014, March 10). A shocking diet: Researchers describe microbe that 'eats' electricity. ScienceDaily. Retrieved March 11, 2014 from www.sciencedaily.com/releases/2014/03/140310144000.htm
This article was a very interesting read. These microorganisms are somehow capable of using genes to pull electrons through the earth using metals in the earth as conductors. The researchers found that the removal of one particular gene decreased the microorganisms’ ability to pull electrons by around 30%. It is fascinating that these microorganisms can use cellular structures as a type of positively charged magnet to pull these electrons. I thought it was fascinating how the researchers wanted to use these microorganisms in a type of fuel cell. It will be interesting to see in the future if they can successfully upscale this process to make it an efficient manner of bio-electric production. The authors of this article also stress the importance of this discovery in understanding biogeochemical cycles and processes. These microorganisms are capable of creating rust out of iron and creating metal circuits in the earth. It will be interesting to see if other microorganisms share this ability or something similar to it.
ReplyDeleteIs “uber” your favorite word? I think this article was very interesting, although I have yet to study the great and wonderful course: Biochemistry. I also liked their literary reference: "When you think about electricity and living organisms, most people default to Mary Shelley's Frankenstein, but we've long understood that all organisms actually use electrons -- what constitutes electricity -- to do work."
ReplyDeleteI had no idea that there are microbes that use extracellular electron transfer (EET). I do not think we really study how bacteria get energy, so this article was nonconventional. Somehow, the microbes are able to take up electricity by using iron to provide the electrons they need to fuel energy production. When the researchers attached an electrode to the bacterial colonies, they observed that the microbes could absorb electrons from a non-ferrous source. This implies that the bacteria may also use other electron-rich minerals like other metals and sulfur compounds to get their energy in the wild.
The weird part is that these microbes rely on sunlight to help produce energy, but the iron they require is found way below the surface in the sediment layers. These microbes have developed an unusual strategy to collect the iron by converting naturally occurring conductive minerals into iron oxide crystals, which collect in the surrounding soil. Over a period of time, those crystals become conductive and act as circuits that enable microbes to oxidize minerals they wouldn't have been able to reach. Therefore these microbes are able to absorb electrons to produce something! I wonder how this could be used to aid public health?
This article was vey interesting to read for the simple reason that bacteria are commonly used in science for research. I found it to be fascinating how the microbes were observed to absobs electrons from a non-ferrous source. It was also interested how the researchers were able to learn how the sunlight dependent microbes were able to locate and use iron that is found to be deep into the earth's soil. The researchers found that inorder to do so the microbes take up electrons through natrully occuring conductive metals. As the microbes pull the electrons from the iron they are able to create iron oxidized crystals which percipitate into the soil around them. With time the iron oxidized crystalls from a cirucit which allows the microbs to pull and use electrons that it would not have otherwise be able to reach. Nature truly is an incredible creation.
ReplyDeleteFirst of all, the picture from the website (although just an artistic depiction) is super cool! The idea of eating to gain energy is not a new concept since we do this every single day. However, microbes eating electricity is quite revolutionary. Rhodopseudomonas palustris does not quite sit down at the dinner table and “eat” the electricity, but it does draw electrons toward itself from far away, so it can still absorb sunlight from the surface of soil, which it needs to survive.
ReplyDeleteThese microbes rely on the iron that they get from the soil to fuel their energy generation, however, the article mentions that iron is not essential to this process. These microbes can draw their electrons from other minerals as well, so if there is a lack of iron they can still produce their energy. Furthermore, the microbe’s ability to do this is dependent upon their genes, but lack of a specific gene decreased its ability to uptake electrons by a third. If the microbe cannot produce energy it cannot survive, so this gene could be a potential target. However, the more interesting use of this knowledge is the potential use for these bacteria to conduct energy through an electrode to be used in the pharmaceutical industry.
What is of interest to me, though, is how the microbe draws electrons unto itself. Scientists speculate that the microbe takes up electrons through conductive minerals. As they pull electrons away from iron they create iron oxide crystals that precipitate and act as a circuit. I’d be interested in a more detailed description of how it does this. To know that it makes such good use of its surrounding resources though is quite incredible!