Consider the life of a nematode: Caenorhabditis elegans, a diminutive, soil-dwelling, hermaphroditic worm that has had its entire genetic code (all base pairs) mapped. Coupled with its reproductive potential, this creature makes a perfect lab specimen. Each worm can expect to live for only a few weeks—unless it is lucky enough to reside in an atmosphere laced with small quantities of hydrogen sulfide. At concentrations of just 50 parts per million, the toxic gas can extend worm longevity by as much as 10 days.
"They were able to withstand higher temperatures than animals that did not have hydrogen sulfide and they were more long lived," says biologist Mark Roth of the Fred Hutchinson Cancer Research Center in Seattle, who teamed with Hutchinson biologist Dana Miller on the study. "They lived 70 percent longer, which is considerably longer. If you add 70 percent to your own life that's a lot."
There is currently no reason to believe that hydrogen sulfide, which is deadly at high concentrations, will have the same effect on humans, although Roth and others have shown that it can put mice into a state of suspended animation. Roth and his colleagues are currently assessing the safety of low concentrations of the gas in humans in order to assess its potential to place removed organs into a state of suspended animation for longer, better storage prior to transplant or even to put critically injured patients into the state to enable more time for lifesaving interventions.
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That potential remains unproved and, in this case at least, H2S has rendered surprising results. Contrary to Roth's expectations, the worms thrived instead of entering a suspended state when exposed to the gas. And when subjected to high temperatures (95 degrees Fahrenheit, or 35 degrees Celsius), those in the more sulfurous atmospheres lived eight times longer than their peers.
The biologists are not sure exactly why this occurs but they did discover that the benefits of H2S were lost when they removed the gene known as sir-2.1—linked to long life. "It's a demonstration of the requirement or need for that gene product to have sulfide work its magic," Roth says.
The ultimate goal, he says, is to understand the role H2S plays in maximizing survival, whether in worms, mice or, potentially, people. But the long history of the healing effect of natural sulfur springs—volcanic fissures that emit sulfurous water and gases, such as H2S—attests to the fact that the tiny nematode is certainly not the first hint that hydrogen sulfide might have beneficial properties.