Doing it in the dark by Christina Kellogg

green_sulfur_bact.jpgPhotosynthesis, that is. Get your mind out of the gutter! This admittedly sexy anaerobic green sulfur bacterium is capable of photosynthetic growth in the dark ocean depths. It’s able to use geothermal radiation from black smoker hydrothermal vents as a light source, making it the only photosynthetic organism known to use a light source other than sunlight.

Just as hot electric-stove elements radiate light, black smokers glow dimly as 400 degrees C fluid emerges. Most of the glow lies in the infrared spectrum, which the microbes can’t absorb, but part of the light reaches the edge of the visible spectrum. The microbes appear to eke out a living from that light, which the researchers can see only through night goggles.

“It expands our vision of possible environments where you could have photosynthesis,” says biochemist Robert Blankenship of Arizona State University in Tempe.

Apparently, telling these bacteria to ‘stick it where the sun don’t shine’ doesn’t have the same derogatory connotations typically implied.


Thermal image of ‘vent glow’ taken on the Juan de Fuca Ridge, credit John Delaney, University of Washington

See also Beatty et al. (2005) An obligately photosynthetic bacterial anaerobe from a deep-sea hydrothermal vent. PNAS 102(26): 9306-9310.

Image credit: Magnified image of green sulfur bacterium, credit Lars Juul

Dr. M (1729 Posts)

Craig McClain is the Assistant Director of Science for the National Evolutionary Synthesis Center, a National Science Foundation supported initiative. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web. His forthcoming book, Science of the South (, connects cultural icons of South such as pecan pie with the science behind them.

2 comments on “Doing it in the dark by Christina Kellogg
  1. “the only photosynthetic organism known to use a light source other than sunlight”
    My husband just read this post and told me I was mistaken…he pointed out that many marijuana plants (photosynthetic organisms) are grown indoors with artificial light. I consider this a technicality since the artificial light is doing its best to imitate sunlight, however, I concede that he has a point of sorts.

  2. Funny, I don’t recall your husband being one of my college house mates ;^)

    Thanks for the this post. I found this part of the linked article by Naila Moreira a fascinating area of inquiry:

    Researchers have speculated that organisms first developed photosynthesis near hydrothermal light, not sunlight, says John Allen of Queen Mary University of London. “Photosynthesis might be much older than most people think,” he says.

    But DNA analysis suggests that the newly discovered bacterium is a cousin, not a forefather, of modern green-sulfur bacteria that live in sunlit, low-oxygen marine environments. Because all these bacteria are better suited to collect sunlight than infrared light, the just-discovered microbe’s ancestors probably evolved photosynthesis in sunlit regions, says coauthor J. Thomas Beatty of the University of British Columbia in Vancouver. A few pioneer bacteria could then have washed down to deep-sea vents and found a home, he says.

    I especially love the closing quote from Blankenship, “‘Where there’s light, there’s photosynthesis’ is the take-home lesson.”

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