Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Evolution upset: Oxygen-making microbes came last, not first

25.10.2002


Get ready to rewrite those biology textbooks – again. Although the "lowly" blue-green algae, or Cyanobacteria, have long been credited as one of Earth’s earliest life forms and the source of the oxygen in the early Earth’s atmosphere, they might be neither.

By creating a new genetic family tree of the world’s most primitive bacteria and comparing it to the geochemistry of ancient iron and sulfur deposits, Carrine Blank of Washington University has found evidence that instead of Cyanobacteria being very ancient, they may have appeared much later, perhaps as much as a billion years later, than previously assumed. Blank will present the results of her research at the annual meeting of the Geological Society of America in Denver on Tuesday, Oct. 29.

"What paleontologists and geologists have had to do is reconstruct evolutionary events because biologists haven’t had a very good evolutionary tree of bacteria," says Blank. To get a better family tree, Blank took advantage of growing genome archives and studied 38 genes in the whole gene sequences of 53 species of extant bacteria, including Cyanobacteria. By mapping out the rates of change in the slowest-changing genes, Blank was able to generate a bacterial evolutionary history that shows cyanobacteria branching off last.



If correct, Blank’s tree essentially flip-flops the traditional order in which bacteria appeared on the scene.

Traditionally, it has been thought that Cyanobacteria came on stage very early in Earth’s history, perhaps at least 3.5 billion years ago. They produced the first abundant oxygen molecules. All that oxygen bound to the abundant free iron in the oceans and rained to the seafloor – creating the economically important banded iron formations. The advent of atmospheric oxygen also caused sulfide minerals on land to break down into sulfates and wash into the oceans – where sulfur-loving bacteria gobbled them up. The earliest geological evidence for sulfur bacteria is changes in sulfur isotopes – indicating organisms are preferentially using isotopes of the element – that began about 2.4 billion years ago. This was followed by a sudden rise in oxygen in the atmosphere at about 2.2 or 2.3 billion years ago.

"The (traditional) model was that the cyanobacteria were present all the time," says Blank. Reasonable as all this sounds, it doesn’t match the genetic evolutionary tree, she says.

In Blank’s version of the story, the sulfur-loving bacteria came on the scene at about 2.4 billion years ago, and the Cyanobacteria came along at least 100 million years later, she says. Because banded iron formations were formed much earlier than these dates, Cyanobacteria are not likely to have led to their creation, she explains.

Blank’s model could explain the puzzling lack of actual cyanobacteria fossils in the earliest days of the banded iron formations. It could also resolve an apparent contradiction regarding the biochemistry of Cyanobacteria, says Blank. The contradiction is that cyanobacteria have a surprisingly advanced biochemistry that was the product of a long evolutionary history. In other words, cyanobacteria must have evolved from more primitive photosynthetic bacteria.

If Blank is correct, her revised evolutionary history of the bacteria raises a difficult question: If cyanobacteria came later, where did the Earth’s earliest oxidants come from which produced banded iron formations? There are many competing theories on this matter, Blank says. Among them are hypotheses that call on inorganic reactions in the oceans and the air to release limited amounts of oxidants. There is even the possibility that there was also an early and so-far undiscovered iron oxidizing microbe that may have produced banded iron formations as a result of their metabolism, Blank says.

Blank’s cyanobacteria research was conducted as part of her recent doctoral thesis at the University of California at Berkeley. Her bacterial phylogeny research is currently under review for publication in the journal Molecular Phylogenetics and Evolution. Blank is an Assistant Professor of Molecular Geobiology in the Department of Earth and Planetary Sciences at Washington University in St. Louis.


CONTACT INFORMATION

During the GSA Annual Meeting, Oct. 27-30, contact Christa Stratton at the GSA Newsroom in the Colorado Convention Center, Denver, Colorado, for assistance and to arrange for interviews: 303-228-8565.

The abstract for this presentation is available at: http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_46069.htm

Post-meeting contact information:

Carrine Blank
Earth and Planetary Sciences
Washington University
blank@levee.wustl.edu
314-935-4456

Ann Cairns
Director of Communications
Geological Society of America
acairns@geosociety.org
303-357-1056


Ann Cairns | EurekAlert!
Further information:
http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_46069.htm

More articles from Life Sciences:

nachricht 'Lipid asymmetry' plays key role in activating immune cells
20.02.2018 | Biophysical Society

nachricht New printing technique uses cells and molecules to recreate biological structures
20.02.2018 | Queen Mary University of London

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

'Lipid asymmetry' plays key role in activating immune cells

20.02.2018 | Life Sciences

MRI technique differentiates benign breast lesions from malignancies

20.02.2018 | Medical Engineering

Major discovery in controlling quantum states of single atoms

20.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>