Theoretical origin of life: nireogen fixation (Introduction)

by David Turell , Wednesday, February 18, 2015, 22:11 (3566 days ago) @ David Turell

Life must fix nitrogen from the atmosphere to form living matter:-"Past genetic analysis of nitrogen-fixing enzymes, which would have been produced by the microbes, placed their origin at between 2.2 billion and 1.5 billion years ago. Now, scientists looking at some of the planet's oldest rocks have found evidence that life was already practicing nitrogen fixation about 3.2 billion years ago, nearly three-quarters of the way back to the birth of the planet. [Photo Timeline: The Birth of Planet Earth]-"It is fascinating to imagine that this complex metabolic process has been operating on the Earth for over 3 billion years," lead study author Eva Stüeken, a geobiologist at the University of Washington in Seattle, told Live Science."-"Chemical analysis of the rocks suggests that nitrogen was being fixed by the most common of the three kinds of nitrogen-fixing enzymes that exist nowadays — an enzyme that contains the element molybdenum.-"Molybdenum is now abundant because oxygen reacts with rocks to convert molybdenum into a soluble form that can wash into the ocean. However, its source on the ancient, oxygen-poor Earth, is uncertain. The researchers suggested that their findings may be evidence that some early life may have existed as single-celled layers on land. Those microbes would have emitted small amounts of oxygen as a byproduct when they broke down nitrogen, the researchers said. Then, the emitted oxygen would have reacted with any molybdenum in the rock, thus helping to release the element into the water."-
http://www.livescience.com/49850-microbes-on-early-earth.html?cmpid=559085