Harsh Arizona Cave System Home To Hardy Communities Of Bacteria
November 22, 2013

Harsh Arizona Cave System Home To Hardy Communities Of Bacteria

Ranjini Raghunath for redOrbit.com - Your Universe Online

The Kartchner caverns in southeast Arizona are famous for their spectacular limestone rock formations, created by groundwater seeping and dissolving bedrock compounds over thousands of years. For all their beauty, the caverns are extremely harsh environments with no sunlight and precious little water and air, and have shown very few signs of life – until recently.

Amid the quiet and the dark, an entire ecosystem of hardy microbes lives and thrives, according to a new study published in the journal of the International Society for Microbial Ecology.

"We discovered all the major players that make up a typical ecosystem," stated Julie Neilson, University of Arizona associate research scientist and co-author of the study, in a release. "From producers to consumers, they're all there, just not visible to the naked eye."

Among the newly discovered bacteria are previously unknown species as well as those that have potential for environmental clean-up solutions and drug development, the paper reported.

One rare species, for example, has never been cultured in the lab and has only been found in extremely harsh environments such as a sewage treatment plant in Australia and a hydrocarbon-contaminated site in France. Another abundant microbe was related to the bacteria that produce the antibiotic erythromycin, the researchers noted.

Bacteria living above the ground can trap the sun’s energy and carbon dioxide to make food. Bacteria in the Kartchner caverns, however, have no access to sunlight or running water. Instead, they survive off nutrients found in drip water and energy trapped in dead organic matter leaching down from the surface, as well as minerals dissolved in the rocks, the researchers found.

In contrast to other underground bacteria that live under the surface of forests or grasslands, these bacteria live below the desert which has even less to offer in terms of resources, the paper reported.

The Kartchner caverns have a “thousand times less carbon coming in with the drip water,” compared to caves in temperate areas such as Kentucky or West Virginia, Neilson stated.

Without a reliable source of carbon, the bacteria use nitrogen-based compounds such as ammonia instead to make food. Some were also found to dissolve rock and take energy from minerals such as manganese or pyrite.

"It shows the flexibility of microbes," Neilson stated. "They have conquered every niche on the planet."

Another surprising fact was the diversity of the population, according to Raina Maier, University of Arizona professor and senior author of the study. Not one but many different types of bacteria were found to thrive under the harsh conditions, almost half as many as those found above the ground, she noted.

The authors spent years studying the cave formations and swabbing the rocks for DNA samples. Their research was often hampered by the difficulty of recovering DNA samples from such a “starved” environment; at times, they were barely able to scrape together the minimum amount required for a simple analysis.

The presence of these bacteria indicates that there are yet-to-be-found organisms living in other such “extreme and poorly studied environments” with untapped potential, the researchers believe.

"This suggests there are many microbes out there in the world that we know almost nothing about," Neilson stated.