Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

DNA of bacteria crucial to ecosystem defies explanation

23.04.2015

Scientists have found something they can't quite explain in one of the most barren environments on Earth: a bacterium whose DNA sequence contains elements usually only found in a much higher organism.

Trichodesmium is a type of bacteria known as an oligotroph, meaning that it can survive in incredibly nutrient-poor regions of the ocean. In fact, it thrives there -- to the point that great blooms of the microorganism can be seen both with the naked eye and from satellites in space, earning it the name "sea sawdust" from ancient mariners.


This image shows a colony of Trichodesmium.

Courtesy of John Waterbury/Woods Hole Oceanographic Institution

This is because Trichodesmium is a "nitrogen fixer" -- it makes harsh environments more habitable by turning nitrogen gas from the air into ammonium, a nutrient that other organisms can use. It's foundational to the entire food web of the ocean and therefore an important organism for scientists to understand.

By sequencing multiple Trichodesmium genomes -- and using a wide variety of samples to ensure that there was no error -- researchers found that only about 63 percent of the bacteria's genome is expressed as protein. That's an incredibly low amount for a bacterium and unheard of for a free-living oligotroph.

"Our study adds another wrinkle to this enigmatic organism's story," said Eric Webb, associate professor at the USC Dornsife College of Letters, Arts and Sciences and corresponding author of a study on the finding.

In a paper published in March in the Proceedings of the National Academy of Sciences, Webb and his colleagues revealed that Trichodesmium's DNA defies common evolutionary dogma, meaning that there's either an important piece of the puzzle still missing or that the understanding of the evolution of microbial genomes needs to be revisited.

"The unique evolutionary path reflected in this genome contradicts nearly all accounts of free-living microbial genome architectures to date," said lead author Nathan Walworth, a Ph.D. candidate at USC. "Different evolutionary paths are foundational to all arenas of biology, including biotechnology, so it is important for the field to be cognizant of different paths a living organism can take to achieve ecological success."

When scientists first started sequencing genomes in the last century, they found that not every part of the DNA strand encoded a protein to be expressed. In fact, we now know that only about 2 percent of the human genome is expressed -- the rest was initially called "junk DNA."

Scientists now describe it as "non-coding DNA," a nod to the fact that functions have been defined for many of these regions; however, there is still controversy on the extent and role of these regions.

Despite the uncertainty, higher organisms -- like humans -- with tiny populations are highly vulnerable to sweeping mutations and thus can contain a lot of non-coding DNA.

Lower organisms with huge populations -- like bacteria -- are far less susceptible to sweeping mutations and accordingly have been shown to have genomes that are about 85 percent protein coding.

Oligotrophs, in particular, shun non-coding DNA, possibly because of the high energy-cost of living in a harsh environment. Cells need every ounce of energy simply to replicate and survive.

Trichodesmium, as Webb and his team discovered, breaks the mold. Yet despite the novelty of the finding, the ultimate cause of the large non-coding space remains to be defined.

The team theorizes that the high level of non-coding DNA is likely the result of a combination of factors, possibly including the way that Trichodesmium blooms.

Blooms make the species more vulnerable to genetic drift and can lead to genomes with enriched non-coding DNA.

"However, since there are many other bloom-forming cyanobacteria that that do not have expanded non-coding space, blooming ecology is likely not the whole story," Webb said. "Right now, we speculate that interactions with other undefined organisms might also be important."

The surprising and odd nature of Trichodesmium's DNA represents a new and open issue in the study of genetics and one, given the organism's overall importance, that the researchers are eager to answer.

###

The study was completed by scientists from USC, the University of Freiburg in Germany, the Pacific Northwest National Laboratory, the Woods Hole Oceanographic Institution, the Joint Genome Institute and the Oak Ridge National Laboratory. The research was funded by the National Science Foundation (OCE-1260490).

Media Contact

Robert Perkins
perkinsr@usc.edu
213-740-9226

 @USC

http://www.usc.edu 

Robert Perkins | EurekAlert!

Further reports about: DNA Ecosystem Trichodesmium bacteria explanation genomes microbial mutations nitrogen non-coding non-coding DNA

More articles from Life Sciences:

nachricht Decoding the genome's cryptic language
27.02.2017 | University of California - San Diego

nachricht New risk factors for anxiety disorders
24.02.2017 | Julius-Maximilians-Universität Würzburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

New pop-up strategy inspired by cuts, not folds

27.02.2017 | Materials Sciences

Sandia uses confined nanoparticles to improve hydrogen storage materials performance

27.02.2017 | Interdisciplinary Research

Decoding the genome's cryptic language

27.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>