Figure 19.14 What is the Highest Temperature Compatible with Life?

In 2003, Kazem Kashefi and Derek Lovley discovered an extreme thermophile that was isolated from water samples taken 200 miles offshore from Puget Sound in a hydrothermal vent almost a mile and a half deep in the northwestern Pacific Ocean. The researchers sealed samples of unidentified microorganisms and placed them in medium that contained Fe³⁺ as an electron acceptor. The control tubes contained Fe³⁺, but did not contain any microorganisms. Both the experimental and control tubes were incubated for ten hours at 121°C. Following incubation, the tubes were checked for the reduction of Fe³⁺ to Fe²⁺ as magnetite. Using a magnet, the researchers were able to detect magnetite in the experimental tubes, which indicated the presence of living cells. By comparison, no iron-containing solids were present in the control tubes. These results indicated that the experimental conditions were suitable for culturing the high temperature microbe, which they named “Strain 121.” In a second experiment, Kashefi and Lovley grew Strain 121 at a variety of temperatures to determine its optimal growth conditions. Results revealed that the cells multiplied most rapidly at approximately 105°C, but divided about once a day even at 121°C. This finding was quite unexpected because, prior to the discovery of Strain 121, a 15-minute exposure to 121°C was believed to kill all living organisms. The scientists did not detect growth at higher temperatures, but did find that the organism could spend two hours at 130°C and then resume growth when transferred to fresh medium at 103°C. Clearly, Strain 121 is a remarkable organism!

Original Paper

Kashefi, K., and D. R. Lovley. 2003. Extending the upper temperature limit for life. Science 301: 934.
http://www.ncbi.nlm.nih.gov/pubmed/12920290?dopt=Abstract
http://www.geobacter.org/publications/Kashefi934.pdf

Links

Lovley Laboratory
http://www.geobacter.org

Pulse of the Planet: Geobacter: Strain 121
http://www.geobacter.org/press/2004-05-21-pulseplanet.mp3

National Public Radio: Microbe raises heat limits for life
http://www.geobacter.org/press/2003-08-19-npr.mp3

Genome News Network: World’s Hottest Microbe: Loving Life in Hell
http://www.genomenewsnetwork.org/articles/08_03/hottest.shtml

National Science Foundation: Microbe from Depths Takes Life to Hottest Known Limit
http://www.nsf.gov/od/lpa/news/03/pr0384.htm

National Geographic: Hottest Life-Form Found: Microbe Thrives When Boiling
http://news.nationalgeographic.com/news/2004/05/0521_040521_extremeheat.html

New York Times: Deep Under the Sea, Boiling Founts of Life Itself
http://www.nytimes.com/2003/09/09/science/deep-under-the-sea-boiling-founts-of-life-itself.html

TIME magazine: The Microbe Master: Getting a Charge out of Mud
http://www.time.com/time/magazine/article/0,9171,993313,00.html

How Stuff Works: How Extremophiles Work
http://science.howstuffworks.com/cellular-microscopic-biology/extremophile.htm

Chin, J. P., et al. 2010. Solutes determine the temperature windows for microbial survival and growth. Proceedings of the National Academy of Sciences 107: 7835–7840.
http://dx.doi.org/10.1073/pnas.1000557107