Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Genome analysis of marine microbe reveals a metabolic minimalist

22.02.2010
Flightless birds, blind cave shrimp, and other oddities suggest a "use it or lose it" tendency in evolution. In the microbial world, an unusual marine microorganism appears to have ditched several major metabolic pathways, leaving it with a remarkably reduced set of genes.
This metabolic minimalist is a specialist uniquely suited to performing one very important function: taking nitrogen gas from the atmosphere and "fixing" it into a form that makes this essential nutrient available to other organisms. Nitrogen fixation fertilizes the oceans, controlling overall biological productivity and thereby affecting how much carbon dioxide the oceans absorb from the atmosphere.

Jonathan Zehr, the marine microbiologist who discovered the microbe, said it has stubbornly resisted efforts to grow it in the laboratory. But that hasn't stopped his team from determining the complete DNA sequence of its genome. Genome analysis enabled the researchers to reconstruct the organism's unusual metabolic lifestyle. They published their findings in Nature in a paper available online February 21.

Zehr, a professor of ocean sciences at the University of California, Santa Cruz, characterized the microbe as an atypical member of the cyanobacteria, a group of photosynthetic bacteria formerly known as blue-green algae. Still lacking a formal taxonomic classification, it is known only as UCYN-A. First detected in the open ocean near Hawaii in 1998, it is now known to be periodically abundant in tropical and subtropical waters throughout the world.

"Biogeochemists have never been able to balance the nitrogen budget of the oceans--there seems to be more nitrogen produced than we can account for from known organisms. So this organism may be an important part of the overall nitrogen budget," Zehr said.

In a 2008 paper in Science, Zehr's team reported that UCYN-A is completely lacking the genes for a key component of the photosynthetic apparatus . The missing parts, known as photosystem II, carry out the stage in photosynthesis that generates oxygen by splitting water molecules. This is significant because oxygen inhibits nitrogen fixation. Most nitrogen-fixing cyanobacteria carry out photosynthesis during the day and nitrogen fixation at night, but UCYN-A can fix nitrogen all day long.

The new paper extends the list of UCYN-A's missing metabolic pathways to include, among other things, a process central to aerobic metabolism known as the TCA cycle or Krebs cycle. It also lacks the Calvin cycle, which uses the carbon from carbon dioxide to build sugars, and it is unable to synthesize about half of the 20 essential amino acids.

"This thing is really stripped down," said James Tripp, a bioinformatics specialist at UCSC and lead author of the Nature paper. "My analysis indicates it has to have an outside source to obtain sugars, amino acids, and two out of the four bases needed to make DNA."

Tripp performed the genome analysis reported in the paper. He worked closely with scientists at 454 Life Sciences, a Roche company based in Branford, Conn., that specializes in high-throughput DNA sequencing technology. The researchers applied new genome sequencing and assembly techniques to produce the complete genome sequence from natural samples of DNA. Because UCYN-A cannot be cultured, researchers used a cell-sorting technique called flow cytometry to obtain concentrated samples of the microbe from ocean water, and then extracted DNA from the cells for sequencing.

Although UCYN-A must depend on other organisms for key nutrients, the researchers have found no evidence that it lives in a close symbiotic association with another microorganism. Zehr said the failure to find another organism closely associated with it suggests two possibilities. "It might live in a cryptic association that's very hard to sample because it's fragile and just falls apart, or it may respond to blooms of other phytoplankton and live in the soup of nutrients excreted by other organisms," he said.

One of the striking things about UCYN-A's metabolism is that it lacks essential pathways other organisms use to generate energy for their cells. "Nitrogen fixation takes a lot of energy, but this thing has figured out how to fix nitrogen without the normal pathways used to fuel it in other organisms," Zehr said. "It presents a real evolutionary and ecological paradox."

In addition to Zehr and Tripp, the coauthors of the Nature paper include graduate student Shellie Bench, specialist Kendra Turk, and postdoctoral scholar Rachel Foster in Zehr's lab at UCSC, and Brian Desany, Faheem Niazi, and Jason Affourtit of 454 Life Sciences. This research was supported by the Gordon and Betty Moore Foundation, the National Science Foundation, and the NSF Center for Microbial Oceanography Research and Education.

Tim Stephens | EurekAlert!
Further information:
http://www.ucsc.edu

More articles from Life Sciences:

nachricht The irresistible fragrance of dying vinegar flies
16.08.2017 | Max-Planck-Institut für chemische Ökologie

nachricht How protein islands form
15.08.2017 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

Im Focus: Scientists improve forecast of increasing hazard on Ecuadorian volcano

Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science, the Italian Space Agency (ASI), and the Instituto Geofisico--Escuela Politecnica Nacional (IGEPN) of Ecuador, showed an increasing volcanic danger on Cotopaxi in Ecuador using a powerful technique known as Interferometric Synthetic Aperture Radar (InSAR).

The Andes region in which Cotopaxi volcano is located is known to contain some of the world's most serious volcanic hazard. A mid- to large-size eruption has...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

New thruster design increases efficiency for future spaceflight

16.08.2017 | Physics and Astronomy

Transporting spin: A graphene and boron nitride heterostructure creates large spin signals

16.08.2017 | Materials Sciences

A new method for the 3-D printing of living tissues

16.08.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>