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 Seeing on the Quick: New Insights into Active Vision in the Brain
15.08.2018 | Eberhard Karls Universität Tübingen

nachricht New Approach to Treating Chronic Itch
15.08.2018 | Universität Zürich

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

Im Focus: Lining up surprising behaviors of superconductor with one of the world's strongest magnets

Scientists have discovered that the electrical resistance of a copper-oxide compound depends on the magnetic field in a very unusual way -- a finding that could help direct the search for materials that can perfectly conduct electricity at room temperatur

What happens when really powerful magnets--capable of producing magnetic fields nearly two million times stronger than Earth's--are applied to materials that...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

2018 Work Research Conference

25.07.2018 | Event News

 
Latest News

Unraveling the nature of 'whistlers' from space in the lab

15.08.2018 | Physics and Astronomy

Diving robots find Antarctic winter seas exhale surprising amounts of carbon dioxide

15.08.2018 | Earth Sciences

Early opaque universe linked to galaxy scarcity

15.08.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>