“Ancient” Bacteria Use Quantum Mechanics!

The light-harvesting antenna complex of purple bacteria (Click for credit.)

The quantum world is a strange one. In a process called “quantum tunneling,” particles can pass through barriers as if they aren’t there at all. As a result of a process called “perturbation,” empty space can give rise to virtual particles that “blip” into and out of existence. Because of a phenomenon known as “quantum coherence,” a particle can be in several different places at once. These ideas defy common sense, but they have been experimentally verified in many different ways.

It turns out that photosynthesis (the process by which some organisms convert the energy in sunlight into energy that they can use) exploits quantum coherence in an incredible way. When light strikes a photosynthetic organism, its energy must be captured so that it can be used in an amazingly complex process that will convert it from radiant energy into chemical energy. It has long been known that photosynthesis is about 95% efficient when it comes to the first step of capturing light’s energy.1 Until now, however, scientists have not understood how photosynthesis could be that efficient.

After all, harvesting light in a biological environment is difficult. Even though photosynthetic organisms have a well-designed “antenna” system for capturing that light (an example is given above), a living organism is usually in motion. Its environment is also constantly stimulating it in different ways. As a result, even though the antenna system is well designed, it will be distorted and deformed as the organism moves and responds to its environment. This means there should be times when the antenna system is well-aligned, producing very efficient transfer of energy, but there should also be times where it is misaligned, reducing its efficiency. Nevertheless, photosynthesis stays very efficient, regardless of how the antenna complex is distorted.

How does the antenna complex stay efficient? The answer is incredible.

Richard Hildner and his colleagues studied the antenna complex of purple bacteria, single-celled organisms that perform photosynthesis. Unlike plants and many other photosynthetic organisms, they do not produce oxygen as a byproduct of their photosynthesis, and they are generally considered to have very “simple” photosynthetic machinery. As Chandler, Hsin, and Gumbart of the University of Illinois write:

Among all photosynthetic organisms, purple bacteria are considered to have the oldest and simplest photosynthetic apparatus, making them ideal candidates for photosynthetic studies.

What Dr. Hildner and his colleagues found, however, was anything but “simple.” They found that the light-collecting antennae of purple bacteria exploit quantum coherence when they absorb a particle of light (which is called a photon). Because of this, the photon can essentially be everywhere in the antennae at once. What does this mean? It means that regardless of the current state of the antenna, the photon can explore all possible pathways in the absorption process. The most efficient pathway can then be chosen, regardless of how distorted or deformed the antenna might be! As the authors state:2

…long-lived coherences contribute to the necessary robustness against external perturbations and disorder that are ubiquitous in biological systems at physiological temperatures. In this respect, the biological function of these complexes, light absorption and energy funneling toward the reaction center, is optimized for each individual aggregate, and long-lived quantum coherences herein play an important role.

Without exploiting quantum coherence, then, the photosynthesis of purple bacteria would not be as robust. It would vary depending on the specific external perturbations and disorder that happen to be occurring at the time.

Now think about this for a moment. Purple bacteria are supposed to have “simple” photosynthetic machinery. However, even this “simple” machinery is sophisticated enough to exploit quantum mechanics – an esoteric aspect of nature that even most scientists don’t understand. In fact, from an evolutionary point of view, purple bacteria were the first to evolve the process. Nevertheless, they use quantum mechanics!

Now, of course, it is always possible that earlier photosynthetic machinery in purple bacteria was simple and that evolution “tinkered” with the process for billions of years to come up with the ability to exploit quantum mechanics. However, there is no evidence for this. The fact is that the simplest, most “primitive” version of photosynthesis that currently exists in nature has already mastered quantum mechanics. As far as I’m concerned, this provides even more evidence that photosynthesis is the product of an Incredible Designer.

REFERENCES

1. Villy Sundström, “Photosynthetic Light Harvesting, Charge Separation, and Photoprotection: The Primary Steps,” Photobiology: The Science of Life and Light, Lars Olof Björn, ed., Springer 2008, p. 289
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2. Richard Hildner, Daan Brinks, Jana B. Nieder, Richard J. Cogdell, and Niek F. van Hulst, “Quantum Coherent Energy Transfer over Varying Pathways in Single Light-Harvesting Complexes,” Science 340:1448-1451, 2013
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11 Comments

  1. Evan Arcadi says:

    Fascinating! The fact that a non-sentient organism has already mastered something we have only fairly recently discovered is nothing short of mind blowing. This is an awesome tribute to an omniscient creator!

  2. JLAfan2001 says:

    Dr. Wile

    This question is off topic but I’ve asked you questions in the past and I was wondering if you can look this for me? I saw this article by Fazale at Reasons to Believe and I found it unsettling. It seems that new research has found evidence to generate genetic information by natural processes. I think the information may be trivial but it still proves that nature can create a genetic code of sorts. What do you think of it?

    http://www.reasons.org/articles/too-good-to-be-true-evolution-and-the-origin-of-bioinformation

    1. jlwile says:

      Thanks for the link and the question, JLAfan. Dr. Rana is a really bright guy and obviously knows a lot more biochemistry than I do, but I will have to disagree with him on this one. I don’t think the study says anything about how natural processes can create genetic information. I’ll make this study and Dr. Rana’s discussion of it the topic of my next post.

  3. Kendall says:

    What a cool discovery! I don’t know anything about quantum mechanics, but this makes me want to learn! I can’t help but notice the parallel between the phenomenon of quantum coherence and God’s omnipresence. Of course, it could be completely unrelated, but still, it came from God, so cool!

    So this is true for all photosynthetic organisms?

    1. jlwile says:

      Thanks for your comment, Kendall! I’m not sure if quantum coherence is directly related to God’s omnipresence, but there is definitely a parallel.

      In answer to your question, this has only been confirmed for purple bacteria. However, given that they have what is considered the “simplest” photosynthetic machinery, you have to assume that organisms with more complex machinery would also have this feature.

  4. josiah says:

    How hard is it to use quantum effects when you’re a bacterium?
    It’s easy to remark on how we’re just discovering things and they were already using them, but the fact that we’re just discovering things doesn’t on its own make them complicated.

    Imagine if an intelligence based purely on electromagnetic interactions were studying Earth. They may well remark on how our bodies use moments to such effect. For us, being basically rigid jointed structures, the concept of a lever seems almost obvious. For this EM intelligence, quantum phenomena would be everyday observations but levers would still have that almost mystical quality to them.

    1. jlwile says:

      I understand what you are saying, Josiah, but in fact, quantum coherence is actually very unstable. When we study it in the lab, we have to be incredibly careful to keep the system from being disturbed. Most quantum devices in the lab must be cooled to very near absolute zero in order to work. Somehow, these bacteria have a solution that works at normal temperatures when the system is being regularly disturbed. I would call that a major feat of engineering!

  5. Vivielle says:

    We talked about this in my quantum chemistry class. In fact we spent a whole lecture on it. Very cool stuff! God is truly marvelous and great! Something that we learned that I didn’t see mentioned in this post (although it may be in the article you quote from) is that when the photon hits it has to VERY quickly relax just slightly away from its initial energy. It has to relax faster than fluorescence to keep fluorescence from competing with photosynthesis. If I am remembering correctly it very slightly vibrationally relaxes taking it away from fluorescing and giving it time to do what needs to be done for photosynthesis. (I don’t recall the exact times, but I *think* that fluorescence is on the 10^-12 or 10^-13 s timescale so the relaxation has to be faster than that.)

    1. jlwile says:

      That is true, Vivielle. It adds one more level of complexity to the entire process, which is already amazingly complex.

  6. Amy says:

    I heard about this a few months ago when my Plant Phys teacher put a link on one of his slides to an hour long video about this. I tried to watch it but I couldn’t hear anything due to whooshing sound made by the concepts as they flew over my head. Good thing this is written. Though I’ll have to read it a few more times to understand it.
    Alternatively, Perhaps quantum coherences IS a simple process in nature, and we have yet to discover the even more complex mechanisms that “complex” organisms use? Who knows what quantum mechanical shenanigans the universe gets up to.

    1. jlwile says:

      “I couldn’t hear anything due to whooshing sound made by the concepts as they flew over my head.” That’s awesome! More importantly, your point is well taken. Nature is exceedingly complex. Most likely, all of what we know right now is the simple stuff!