New Evidence for the Oldest Oxygen-Breathing Life On Land

New University of Alberta research shows the first evidence that the first oxygen-breathing bacteria occupied and thrived on land 100 million years earlier than previously thought. The researchers show that the most primitive form of aerobic-respiring life on land came into existence 2.48 billion years ago.

The research team, led by U of A geomicrobiologist Kurt Konhauser, made their find by investigating a link between atmospheric oxygen levels and rising concentrations of chromium in the rock of ancient seabeds.

"We suggest that the jump in chromium levels was triggered by the oxidation of the mineral pyrite (fool's gold) on land," said Konhauser.

Pyrite oxidation is a simple chemical process driven by two things: bacteria and oxygen. The researchers say this proves that oxygen levels in Earth's atmosphere increased dramatically during that time.

"Aerobic bacteria broke down the pyrite, which released acid that dissolved rocks and soils into a cocktail of metals, including chromium," says Konhauser. "The minerals were then carried to the oceans by the run-off of rain water.

"Our examination of the ancient seabed data shows the chromium levels increased significantly 2.48 billion years ago," said Konhauser. "This gives us a new date for the Great Oxidation Event, the time when the atmosphere first had oxygen."

The rising levels of atmospheric oxygen fostered the development of new bacteria species, and Konhauser says that, following the evolutionary path back to that first oxygen-breathing life form on land, our ancestors started off in a pool of highly acidic water.

The researchers say the modern analogue for that first primitive oxygen-dependent life form on Earth is still with us.

"The same bacterial life forms are alive and well today, living off pyrite and settling in the highly acidic waste waters of mining sites the world over," said Konhauser.

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