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Scientists Reveal How Microbe 'Eats' Electricity

Some microbes, simple as they may be, have an ability to gather energy from extreme sources like sulfur, formic acid, minerals, and… electricity? Rhodopseudomonas palustris are gram-negative bacteria that has remarkable dexterity in obtaining energy and is able to take cues from the environment to employ photoautotropic, photoheterotrophi
c, chemoautotrophic, or chemoheterotrophic metabolism. This flexibility has baffled microbiologists for some time. Girguis’s team focused on the phototrophic aspects of its metabolism in order to begin teasing out some answers. Electrons are essentially the energy currency for most forms of life and they are exchanged through oxidation-reduction  reactions. R. palustris TIE-1 is somewhat different in that it is able to take electrons from materials in the solid phase, while most others require electron donors and acceptors to be in solution. One of these metabolic mechanisms allows the bacteria to obtain energy through extracellular electron transfer, though the cellular processes that accomplish this have been a mystery until now.  While it has been suggested that these bacteria could be used to create a functional battery, Girguis is not so sure it would be an efficient fuel source. He does note that there is a large opportunity to use them in the pharmaceutical industry where they could be altered to “produce something that is of interest” to researchers and merely need to be fed with electricity.
Yes, electricity. A team led by Peter Girguis from Harvard has discovered how a certain bacteria gets its energetic needs from electrons pulled from the environment. The results of this study were published in Nature Communications.  These bacteria traditionally get electrons from iron, though Girguis was able to show that it wasn’t necessary—a critical breakthrough in understanding R. palustris’s metabolism. When the bacteria were exposed directly to an electrode, they were readily able to uptake the electrons and convert them into energy using carbon dioxide as an electron acceptor. Subsequent experiments showed that a certain gene is responsible for the majority of electron uptake. Without it, the microbe loses 66% of its ability to uptake free electrons. RuBisCo is the protein that is used to convert carbon dioxide into the energy-rich nutrients that the bacteria need. The gene that produces the protein is activated by sunlight, as is much of the ability to take in electrons from the environment. However, the ferrous materials used by the bacteria are below the ground where they would not have access to sunlight. The researchers found that while the bacteria stay on the surface, they are able to draw in electrons from the sediment beneath them and get the best of both worlds.

The existence of dark matter has been known for decades, but working out what it is actually made from has been a frustrating quest. Now, however, Professor David Cline has told a UCLA symposium of the finding of what could be the first cold dark matter particle, an object weighing 30 billion electron volts.  What is needed is “cold dark matter” particles, ones that travel slowly enough that those produced in the big bang would have clumped together in the spots that became modern day galaxies. Every two years UCLA convenes a symposium to discuss progress in the search for dark matter of one form or another. Nothing has yet been published, but Cline, of the home campus’s College of Letters and Science, commented, “At this symposium, it was obvious that excitement is building in the fields of dark matter theory and, especially, detection.”  The Fermi telescope has found mysterious gamma rays, which Cline thinks may be emitted by the particles. Attempts to get WIMPs to interact with atomic nuclei in underground laboratories have failed to find anything, but Cline said, “there is no incompatibility [in these detectors’ null results] with the interesting excess in the FERMI data.”
 
The first evidence for dark matter emerged in 1932 when Jan Oort noted that objects are circling the galactic plane as if our galaxy has substantially more mass than we can see. Further study on other galaxies found the same pattern. Two main theories emerged: Weakly Interacting Massive Particles (WIMPS) or Massive Compact Halo Objects (MACHOs). The first involves subatomic particles with no electromagnetic charge or strong nuclear interaction; the second posits objects the size of planets or stars that don’t shine. The problem is far from trivial. It is estimated that the dark matter we cannot see accounts for more than five times as much mass in the universe as the ordinary matter we can. Over time the weight of scientific support has shifted to the idea that WIMPS account for most of what we are missing, but finding them has been more of a problem. Neutrinos were thought to be the answer, but the neutrinos left over from the formation of the universe travel too fast, and so would be too evenly spread, to account for the mass clumped around galaxies. Subatomic particles are classified by their mass, but by the famous E=mc2 mass can be converted to energy, making electron volts, a unit of energy, often the favored way to describe them. For comparison, protons have a mass of just under a billion electron volts. “Because dark matter makes up the bulk of the mass of galaxies and is fundamental in the formation of galaxies and stars, it is essential to the origin of life in the universe and on Earth,” said Cline.
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