Arsenic Could be Life-Sustaining, Not Life-Threatening
Duquesne University Professor Participates in Study That Challenges Biochemistry Basics
Arsenic, an element that is most often toxic to life, may actually be life-sustaining for some bacteria and a new finding could challenge conventional wisdom about the biochemistry of life as we know it.
The discovery, published Dec. 2 in Science magazine, could have “profound evolutionary and geochemical significance” because it suggests that life can flourish when arsenic is substituted for the phosphorous, an inorganic building block for life, said Duquesne University microbiologist Dr. John Stolz, who was involved in the National Aeronautics and Space Administration (NASA) study.
“It’s tremendously exciting and could really change the paradigm if an element whose various chemical forms are generally quite toxic could support life,” said Dr. David W. Seybert, dean of Duquesne’s Bayer School of Natural and Environmental Sciences, while noting that the research still must be replicated and further verified and validated. “NASA is involved because this finding could imply an alternate or parallel way of evolution of life, which as we know it is based on the elements carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus.”
In the study, led by Dr. Felisa Wolfe-Simon of NASA, an arsenic-resistant microbe from Mono Lake, Calif., was isolated. Without phosphate in the growth medium, cells did not grow. However, when arsenic was provided instead of the phosphorous, the bacteria did grow—and the DNA, proteins and lipids that normally contained phosphorus were found to contain arsenic instead.
Working with undergraduate student Mark Dudash of Mount Lebanon, Stolz examined a strain of the arsenic-grown cells and noticed that they contained large structures such as vacuoles and sacs to store nutrients, unlike the normal phosphate-grown cells.
Overall, this discovery, Stolz said, suggests that life may have experimented with other elements for its building blocks and arsenic could be a key to how life evolved on early Earth, when oxygen was not plentiful.
“Arsenic is typically toxic, and arsenic compounds tend to be much less stable in aqueous systems than phosphate compounds are,” Seybert said. “There must be some unique way that these organisms are stabilizing the arsenic in the macromolecules.”
This finding could have implications about life on other planets, said Stolz. Earlier this year, Stolz received a second grant to continue working on the NASA project at Mono Lake, which is about three times saltier than sea water, about 80 times more alkaline than the ocean and supports an ecosystem rich in arsenic.
“The study is looking at this extreme environment to see what life could possibly be like on other planets,” Stolz said.
Founded in 1878, Duquesne is consistently ranked among the nation's top Catholic universities for its award-winning faculty and tradition of academic excellence. Duquesne, a campus of nearly 9,500 graduate and undergraduate students, has been nationally recognized for its academic programs, community service and commitment to sustainability. Follow Duquesne University on Facebook, Twitter and Instagram.