Bacteria inform origins of life

Two miles beneath Johannesburg, South Africa, rock temperature hovers around 150 degrees. At this depth — about 47 times the height of Fine Tower — humidity nears 100 percent. And in fracture zones — channels in the rock filled with water and methane gas — a team led by geosciences professor T.C. Onstott has discovered a community of unique bacteria that thrives independent of the sun's energy.

After 10 years of research, the team published their findings in the Oct. 20 issue of the journal Science, in a paper titled "Long-Term Sustainability of a High-Energy, Low-Diversity Crustal Biome."

The discovery of bacteria that survive without sunlight raises questions about the origins of life on earth.

"There is a possibility that these bacteria came before oxygen-dependent life forms, but that hasn't been proven yet," Onstott said.

Scientists have long known about microbial communities that survive without direct input from the sun, such as those found near deep-sea volcanic vents. These communities depend at least in part on nutrients that can be traced back to photosynthetic plants or bacteria, however.

The community that Onstott has been studying is the first found to be exclusively dependent on geologically-produced sulfur and hydrogen.

Due to unexpectedly high levels of nutrient concentration, the subterranean environment could "support microbial life in isolation from earth's surface for millions of years," geosciences department chair Bess Ward said in an email.

Onstott and his fellow researchers each took threeto four-week shifts exploring the South African underworld. While on site, Onstott said, they rose early in the morning and then descended two miles in metal cages along with 40 other workers.

Once at the bottom, they hiked for at least another hour through a vast network of tunnels before reaching a fracture zone. After the scientists had extracted samples and returned to the surface, site workers would blast further to extend the tunnel so the researchers could explore the newly-excavated tunnel the next morning.

In addition to its academic appeal, the research may prove to have practical benefits.

Mining is a principal means of income for South Africa and is the source of much contamination that seeps into the ground.

"It turns out that the bacteria's enzymes give them the ability to clean up some of this toxic waste in an efficient manner," Onstott observed.

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"We can transfer the genes that produce the enzymes to other bacteria that can easily reproduce in the environment, then introduce them and let them clean up the waste."

The discovery further raises the possibility of life on Mars, one of Onstott's personal areas of interest.

"You've got rocks, you've got radiation, water and gas. Everything is there to sustain life," he said.

"They can make everything else they need."

"This clearly has implications for other extreme environments on earth, the pace of microbial evolution and the potential for extraterrestrial environments to harbor cryptic life," Ward said.