Microbes everywhere you look (and some other places)

A schematic of a microbial electrolysis cell.

A microbial fuel cell producing hydrogen, Image via Wikipedia

I am always amazed by the incredible diversity of microorganisms; microbiologists have found ecosystems of prokaryotes in essentially every single location they have looked at on the surface of our planet. Recall that when we introduced the topic of microbial nutrition, we said that every living cell must have a source of energy to drive cellular processes, and a source of carbon to construct new cellular material.  The diversity of prokaryotic life is such that many organic and inorganic compounds may be used as a source of energy. As long as a chemical compound has the ability to donate high energy electrons to an appropriate electron acceptor, more than likely there is some microorganism that has the ability to take advantage of that chemical reaction and live off of the energy liberated. However, it has been thought that sediments deep below the surface were inhospitable to life.

A new article published in the journal Geology, and summarized in Science News, suggests that sediments deep below the surface may harbor complete biospheres of novel microorganisms. Researchers at Cardiff University, in Wales, carried out the following experiment: they ground up different minerals such as quartz and basalt and mixed them with water to make a slurry. They added bacteria to some of these slurries, heated them at temperatures up to 100 °C in order to simulate conditions far below the surface of Earth, and let them cook for a while. Samples which had added bacteria began to produce hydrogen gas, while sterilized samples did not produce the gas. The production of hydrogen gas was therefore associated with the presence of the microorganisms mixed with the ground  up minerals. The organisms were assumed to be obtaining their energy needs from the inorganic materials, and liberating hydrogen by splitting water.

Hydrogen production by prokaryotes is not a new thing, and the process is actually a topic of very intense research. The interest is pushed by the need to supplement and replace fossil fuel reserves, and a renewable source of hydrogen is greatly desired. Any new way to make this resource is of great interest. The novel aspect of this is that the biochemistry involved is not well understood, and is apparently occurring in an environment that had not been associated with biological processes.

So will this process be useful from an industrial standing? My first impression is likely not. The microbes were mixed with the mineral sludge for months, with some gradual release of hydrogen gas, but not at the levels we might need to power our car.  I would recommend instead that we appreciate this example of the ability of life to be found in the most incredible and unearthly places.

BONUS:  Suggest a reason why the described experiment is working with ground up rocks, but likely would not generate detectable hydrogen gas with intact rocks. 


About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on February 23, 2011, in Bonus!, Microbes in the News, Strange but True. Bookmark the permalink. 4 Comments.

  1. The ground up rocks are consumed by the bacteria, which gives you protons and electrons and presumably hydrogen gas. Solid rocks would be unable to be consumed by the bacteria because of their size.

    • Presumably, the solid rock is a possible substrate for the biological reaction; it is chemically identical, after all. However, we only observe measurable hydrogen gas production from the ground up rock. What is different between the two situations? I gave a clue there.

  2. I think that the ground up rocks provide more nutrients and can react better with the bacteria because even though we can see the solid rocks better grounding them up makes them easier to absorb with the bacteria. Solid rocks are to big and don’t show the chemical contents inside the rocks like ground up rocks do.

    • The bacteria are not absorbing nutrients from the minerals per se, but are using them in a specific metabolic reaction, which will occur more quickly if you increase the surface area. A large rock has the same amount of the mineral, but when it is ground up, it will have a larger surface area for the reaction to occur!

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