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Home » Biology Articles » Biotechnology » White Biotechnology » New petroleum-degrading bacteria found at Rancho La Brea Tar Pits in Los Angeles


RIVERSIDE, Calif. - Environmental scientists at UC Riverside have discovered that the Rancho La Brea tar pits in downtown Los Angeles, Calif., house hundreds of new species of bacteria with unusual properties, allowing the bacteria to survive and grow in heavy oil and natural asphalt.

Trapped in soil that was mixed with heavy oil nearly 28,000 years ago, the bacteria are uniquely adapted to the pits' oil and natural asphalt, and contain three previously undiscovered classes of enzymes that can naturally break down petroleum products, the researchers report.

"We were surprised to find these bacteria because asphalt is an extreme and hostile environment for life to survive," said Jong-Shik Kim, a postdoctoral researcher in the Department of Environmental Sciences, who initiated the study. "It's clear, however, that these living organisms can survive in heavy oil mixtures containing many highly toxic chemicals. Moreover, these bacteria survive with no water and little or no oxygen."




"Previously, some bacteria had been cultured from the asphalt, but no one had been able to extract DNA from the asphalt to study the entire microbial community," said Kim, the first author of the paper.

Providing a natural observatory for the unusual bacteria, the Rancho La Brea tar pits, which formed in the last ice age, are located in Hancock Park, Los Angeles. Rancho La Brea, one of the world's fossil localities, is recognized for having the largest and most diverse assemblage of extinct ice age plants and animals in the world.

"The living bacteria contained in the asphalt are most likely the progeny of soil microorganisms that were trapped in the asphalt, although some may also have been carried to the surface in the heavy oil that seeped upwards from deep underground oil reservoirs," said Crowley, the research paper's other author.



"One family that was represented by many species is related to a group of bacteria that are the most radiation-resistant organisms on the planet," Crowley said. "Indeed, this family of bacteria has been previously investigated by the Department of Energy for cleanup of hydrocarbon contamination in radioactive environments."

It was the continual production of bubbles of methane gas that come up through heavy oil overlying the asphalts that clued the researchers to the presence of bacteria in the asphalt. "In the absence of oxygen, methane is produced by bacteria that use carbon dioxide for respiration instead of oxygen," Crowley explained.

He noted that the bacteria are not uniformly distributed in the tar pits. While one reason for their presence could be bacteria rising through the soil via a subterranean oil flow, other explanations are possible. "Probably there has also been genetic exchange and natural selection of new species over the thousands of years the bacteria have been living in the asphalt," Crowley said.



University of California - Riverside. May 2007.

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