Electric life forms that feed pure energy
Place an electrode in the ground, pump some electrons down and it will appear: alive cells that eat electric energy. We know bacteria that can survive thanks to different energy sources, but none of them isn’t as unusual as this electric bacteria.
Think about Frankenstein’s monster which can be brought to live with galvanic energy, but keep in mind that these “electric bacteria” are real and can be found everywhere.
Unlike other life forms on Earth, the electric bacteria use the energy in its purest form, electricity as electrons obtained from rocks and metals. We already knew about two types of bacteria like this: Shewanella and Geobacter.
Now the biologists show us that they can attract more electrons from rocks and marine mud, tempting them with some electricity. The experiments realized by the biologists showed that these bacteria can grow on electric battery electrode, proving this way that these amazing life forms eat and eliminate electrons.
Thins thing shouldn’t be a surprise, says Kenneth Nealson from University of Southern California in Los Angeles. We already know that life is a flux of electrons: “we eat sugars that have an excess of electrons and we breathe oxygen that is gladly accepting them”. The cells in our bodies decompose the sugars and the electrons pass through these in a variety of chemical reactions until they reach the oxygen that needs them.
In the process, the cells create an ATP molecule that works as a unit of energy storage for almost all forms of life. The movement of electrons represents an essential condition in formation of an ATP molecule. “Life is very intelligent”, says Nealson. “In this way we figure out how to obtain electrons from food and we can control them.”. In most of the life forms, the organism stores the electrons in molecules that can transport them safely through cells, until they are released in the breathed oxygen.
“This is the way we get the energy needed by the body and any form of life on this planet uses this process”, says Nealson. “Electrons must move in order to obtain energy. That’s why a person that remains without oxygen dies within a few minutes. Without the oxygen needed to survive, electrons don’t move through the body.”
The discovery of these bacteria shows that some forms of life don’t need sugar anymore and can use energy in its purest form, electrons, that are captured from mineral’s surface. “It is something unprecedented”, says Nealson. “In some way, we can think at an extra-terrestrial life”.
Nealson’s team is one of the few biologist teams that managed to grow these bacteria directly on electrodes, keeping them alive with electric energy and nothing else, like sugars or any kind of nutrients. A human equivalent of this process, says he, it would be that we plug in our fingers to get some energy.
In order to grow the bacteria, the team of biologists collected sediments from the seabed and used them into lab-experiments. Later, they out the electrodes in these sediments.
First, the biologists measured the electric tension that naturally exists in these sediments, before applying a slightly different tension. An electric tension a bit higher than the natural one generates an excess of electrons, a lower tension meaning that the electrode will easily accept electrons generated by other electricity source.
The bacteria from sediments can “eat” electrons generated by a higher tension or can “breathe” electrons out of a electrode with a lower tension, generating electric current. This current is analyzed by researchers, representing a sign of the presence of a life form that the researchers captured.
“In principle, the idea is to take these sediments, to put the electrodes inside and then to ask ourselves: OK, who likes this thing?”, says Nealson.
An unusual breathing
At the Goldschmidt Geoscience Conference that took place in Sacramento, California, Shiue-lin Li from the Nealson’s laboratory presented the results of the experiments on growth of these electric bacteria in sediments collected near Santa Catalina Island from California. Also, Yamini Jangir from University of Southern California presented the results of different experiements on growth of these electric bacteria from Death Valley situated in Mojave Desert, California.
Daniel Bond and his co-workers from University of Minnesota published their experiments that show that they managed to grow a certain type of bacteria that captures electrons from an iron electrode. This research, says Moh El-Naggar who is the supervisor of Jangir, can be the most conclusive argument that we have until now about the existence of energy eating bacteria and which were cultivated on a source of electrons, without other nutrients.
But Nealson says that much more data about these life forms will be published. His PhD, Annette Rowe, identified eight different types of bacteria that use electric energy. These results are about to be published.
Nealson is thrilled about Rowe’s identification on so many types of electric bacteria, all very different between them and none of them alike Shewanella or Geobacter. “This thing is very important. From here results that here exists a whole part of bacterial world that we know nothing about.”
The discovery of this hidden biosphere represents the reason why Jangir and El-Naggar want to grow electric bacteria. “We use electrodes to simulate the interactions between them”, says El-Naggar. “We grow something that could not be grown until now, if you want”. The researchers want to install a battery inside gold mine from South Dakota to see what could live there.
NASA is also interested in life forms that can live underground because these organisms can easily survive with little energy and can indicate the presence of life forms in other regions of the solar system.
Yet, electric bacteria could have a practical use even here on Earth, like biomachines that can clean residual waters or contaminated underground waters, obtaining their energy sources from the environment. Nealson calls them self-powered useful devices – SPUD.
Practically, another interesting perspective is to use these electric bacteria to try to answer to some fundamental questions about life, like “what is the minimum energy needed to sustain life”.
In the next step of the experiments, says Yuri Gorby, a microbiologist from Rensselaer Polytechnic Institute in Troy, New York we need to cultivate the bacteria not only on one electrode, but in the space between two electrodes. These bacteria practically eat electrons from one electrode and uses them as a source of energy and then throws them on the other electrode.
Gorby thinks that the bacteria that eat and breathe electrons will be discovered soon. “An electric battery that evolves between two electrodes could live forever”, says Gorby. “If it won’t be eaten or destroyed, theoretically, we could keep that organism alive indefinitely”.
Also, it is possible to vary the tension applied to the electrodes to reduce the energy available to these bacteria until a minimum of energy needed to survive is reached. In this situation, the cells wouldn’t be capable to reproduce or to grow, but they could still be used to maintain machines made of these cells. “For them, this energy could mean survival”, says Gorby.
How much battery??? liquid is necessary in order to keep an electric battery alive? Answer this question and you will answer one of the most fundamental questions about life.
Wire in the mud
Electric batteries have different shapes and sizes. A few years ago, biologists found that some of them make filaments like hairs that work like electric wires for the transfer of electrons forward and backward between cells and the environment. These are called bacterial nanowires.
Lars Peter Nielsen and his o-workers from Aarhus University from Denmark found that ten thousands of electric bacteria can merge to form chains that transport electrons across centimeter distances, a huge distance for a bacteria of 3-4 micrometres. This means that bacteria that live in the seafloor mud where the oxygen doesn’t reach, can access the oxygen dissolved in the water, holding hands with their friends.
These bacteria can be found wherever we look, says Nielsen. A simple way to find out if you are near these electrons consumers is to put a certain amount of left over in a small dish full of water and then gently swirl it. The dirt must fall apart. If not, then probably the wires formed by these bacteria held them together.
Here it’s about more than fun. The first experiments showed that this type of cables conduct electricity as well as the wires that connect your toaster to a plug. This observation could open up new interesting research directions on flexible lab-grown biocables.