Navigation Links
Scientists decipher 3 billion-year-old genomic fossils

About 580 million years ago, life on Earth began a rapid period of change called the Cambrian Explosion, a period defined by the birth of new life forms over many millions of years that ultimately helped bring about the modern diversity of animals. Fossils help palaeontologists chronicle the evolution of life since then, but drawing a picture of life during the 3 billion years that preceded the Cambrian Period is challenging, because the soft-bodied Precambrian cells rarely left fossil imprints. However, those early life forms did leave behind one abundant microscopic fossil: DNA.

Because all living organisms inherit their genomes from ancestral genomes, computational biologists at MIT reasoned that they could use modern-day genomes to reconstruct the evolution of ancient microbes. They combined information from the ever-growing genome library with their own mathematical model that takes into account the ways that genes evolve: new gene families can be born and inherited; genes can be swapped or horizontally transferred between organisms; genes can be duplicated in the same genome; and genes can be lost.

The scientists traced thousands of genes from 100 modern genomes back to those genes' first appearance on Earth to create a genomic fossil telling not only when genes came into being but also which ancient microbes possessed those genes. The work suggests that the collective genome of all life underwent an expansion between 3.3 and 2.8 billion years ago, during which time 27 percent of all presently existing gene families came into being.

Eric Alm, a professor in the Department of Civil and Environmental Engineering and the Department of Biological Engineering, and Lawrence David, who recently received his Ph.D. from MIT and is now a Junior Fellow in the Harvard Society of Fellows, have named this period the Archean Expansion.

Because so many of the new genes they identified are related to oxygen, Alm and David first thought that the emergence of oxygen might be responsible for the Archean Expansion. Oxygen did not exist in the Earth's atmosphere until about 2.5 billion years ago when it began to accumulate, likely killing off vast numbers of anerobic life forms in the Great Oxidation Event.

"The Great Oxidation Event was probably the most catastrophic event in the history of cellular life, but we don't have any biological record of it," says Alm.

Closer inspection, however, showed that oxygen-utilizing genes didn't appear until the tail end of the Archean Expansion 2.8 billion years ago, which is more consistent with the date geochemists assign to the Great Oxidation Event.

Instead, Alm and David believe they've detected the birth of modern electron transport, the biochemical process responsible for shuttling electrons within cellular membranes. Electron transport is used to breathe oxygen and by plants and some microbes during photosynthesis when they harvest energy directly from the sun. A form of photosynthesis called oxygenic photosynthesis is believed to be responsible for generating the oxygen associated with the Great Oxidation Event, and is responsible for the oxygen we breathe today.

The evolution of electron transport during the Archean Expansion would have enabled several key stages in the history of life, including photosynthesis and respiration, both of which could lead to much larger amounts of energy being harvested and stored in the biosphere.

"Our results can't say if the development of electron transport directly caused the Archean Expansion," says David. "Nonetheless, we can speculate that having access to a much larger energy budget enabled the biosphere to host larger and more complex microbial ecosystems."

David and Alm also went on to investigate how microbial genomes evolved after the Archean Expansion by looking at the metals and molecules associated with the genes and how those changed in abundance over time. They found an increasing percentage of genes using oxygen, and enzymes associated with copper and molybdenum, which is consistent with the geological record of evolution.

"What is really remarkable about these findings is that they prove that the histories of very ancient events are recorded in the shared DNA of living organisms," says Alm. "And now that we are beginning to understand how to decode that history, I have hope that we can reconstruct some of the earliest events in the evolution of life in great detail."


Contact: Denise Brehm
Massachusetts Institute of Technology, Department of Civil and Environmental Engineering

Related biology news :

1. Jefferson scientists deliver toxic genes to effectively kill pancreatic cancer cells
2. Scientists identify novel inhibitor of human microRNA
3. Argonne scientists peer into heart of compound that may detect chemical, biological weapons
4. MU scientists go green with gold, distribute environmentally friendly nanoparticles
5. Scientists identify gene that may contribute to improved rice yield
6. Scientists discover why a mothers high-fat diet contributes to obesity in her children
7. MU scientists see how HIV matures into an infection
8. Earth scientists keep an eye on Texas
9. Thinking it through: Scientists call for policy to guide biofuels industry toward sustainability
10. Scientists identify a molecule that coordinates the movement of cells
11. Scientists Find new migratory patterns for Mediterranean and Western Atlantic bluefin tuna
Post Your Comments:
Related Image:
Scientists decipher 3 billion-year-old genomic fossils
(Date:6/20/2016)... , June 20, 2016 Securus Technologies, ... technology solutions for public safety, investigation, corrections and ... prisons involved, it has secured the final acceptance ... facilities for Managed Access Systems (MAS) installed. Furthermore, ... facilities to be installed by October, 2016. MAS ...
(Date:6/9/2016)... 9, 2016 Paris Police ... video security solution to ensure the safety of people and ... during the major tournament Teleste, an international technology ... services, announced today that its video security solution will be ... back up public safety across the country. The system roll-out ...
(Date:6/2/2016)... NEW YORK , June 2, 2016   The ... (Weather), is announcing Watson Ads, an industry-first capability in which ... advertising, by being able to ask questions via voice or ... Marketers have long ... with the consumer, that can be personal, relevant and valuable; ...
Breaking Biology News(10 mins):
(Date:6/23/2016)... /PRNewswire/ - FACIT has announced the creation of ... company, Propellon Therapeutics Inc. ("Propellon" or "the Company"), ... portfolio of first-in-class WDR5 inhibitors for the treatment ... represent an exciting class of therapies, possessing the ... cancer patients. Substantial advances have been achieved with ...
(Date:6/23/2016)... 2016 Houston Methodist Willowbrook Hospital has ... Association to serve as their official health care ... Willowbrook will provide sponsorship support, athletic training services, ... coaches, volunteers, athletes and families. "We ... Association and to bring Houston Methodist quality services ...
(Date:6/23/2016)... Prostate Cancer Foundation (PCF) is pleased to announce 24 new Young ... cancer. Members of the Class of 2016 were selected from a pool of ... More About the Class of 2016 PCF Young Investigators ... ... ...
(Date:6/23/2016)... , June 23, 2016   EpiBiome , ... secured $1 million in debt financing from Silicon Valley ... up automation and to advance its drug development efforts, ... new facility. "SVB has been an incredible ... the services a traditional bank would provide," said Dr. ...
Breaking Biology Technology: