Nav: Home

A toxic menu

April 17, 2012

In a study published in the journal Proceedings of the National Academy of Sciences, scientists from the Max Planck Institute for Marine Microbiology in Bremen and Greifswald University, together with colleagues from Freiburg, Italy and the USA, have revealed that a small marine worm, faced with a scarce food supply in the sandy sediments it lives in off the coast of Elba, must deal with a highly poisionous menu: this worm lives on carbon monoxide and hydrogen sulphide.

The worm, Olavius algarvensis, can thrive on these poisons thanks to millions of symbiotic bacteria that live under its skin. They use the energy from carbon monoxide and hydrogen sulphide to produce food for the worm. The symbionts do this just like plants by fixing carbon dioxide into carbohydrates but instead of using light energy from the sun, the symbionts use the energy from chemical compounds like carbon monoxide. "They do this so effectively, that the worm has lost its entire digestive system, including its mouth and gut, during the course of evolution, and feeds only through its symbionts", explains Nicole Dubilier, Head of the Symbiosis Group at the Bremen-based Max Planck Institute.

Carbon monoxide and hydrogen sulphide, however, are by no means the only energy sources this worm can live on. Some of the symbiotic bacteria in the worm can take up hydrogen and organic nutrients from the environment, even if these are present in only tiny amounts. Olavius algarvensis also has other tricks up its sleeve that allow it to survive in its nutrient-poor environment: in contrast to most animals, which are not capable of recycling their waste products and must excrete them, the worm can make further use of these, again thanks to its symbiotic microbes. The symbionts are true recycling masters when it comes to use products that still contain a lot of energy for their own purposes, but are no longer any use to the worm. "This is the reason why the worm has been able to not only reduce its digestive system, but also its kidney-like excretory organs", stresses Dubilier, "something that has not been discovered in any other marine animal."

For their investigations, the researchers used a combination of cutting-edge techniques, such as metaproteomics and metabolomics, which make it possible to analyse a large proportion of the proteins and metabolic products in an organism. Metaproteomic analysis presented a particular challenge, as it required the researchers to separate the cells of the symbionts and the host. Thomas Schweder from the Institute of Pharmacy at Greifswald University explains: "Using metaproteomics, we were able to identify thousands of proteins and assign them to the individual partners in the symbiosis. This gave us direct insights into the metabolism of the bacterial symbionts and their interactions with the host."

The researchers were very surprised when their analyses revealed that the worm has large amounts of proteins that allow it to use carbon monoxide as an energy source, because this gas is so poisonous. "Also, we couldn't imagine that carbon monoxide is present in the worm's environments", says Manuel Kleiner, a doctoral student in Nicole Dubilier's research group, "so we were amazed to find such unusually high concentrations of carbon monoxide in the Elba sandy sediments."

Nicole Dubilier has been working with the worm for more than 15 years: "We have known for quite some time that the symbiotic bacteria in Olavius algarvensis can interact with one another to use the energy-rich sulphur compounds to gain energy." But it is only now that the researchers have been able to work out other metabolic pathways - and to discover new energy sources. The study highlights the importance of complementing metagenomic analyses with metaproteomics and metabolomics. "The worm provides us with an example of the power of evolution. Over the course of millions of years, adaptation and selection have led to the development of an optimally adapted host-symbiont system. And these seemingly modest worms are an excellent model for a better understanding of other complex symbioses, such as those of the human gut", says Dubilier.

-end-

Original paper:

Metaproteomics of a gutless marine worm and its symbiotic microbial community reveal unusual pathways for carbon and energy use

Manuel Kleiner, Cecilia Wentrup, Christian Lott, Hanno Teeling, Silke Wetzel, Jacque Young, Yun-Juan Chang, Manesh Shah, Nathan C. VerBerkmoes, Jan Zarzycki, Georg Fuchs, Stephanie Markert, Kristina Hempel, Birgit Voigt, Dörte Becher, Manuel Liebeke, Michael Lalk, Dirk Albrecht, Michael Hecker, Thomas Schweder & Nicole Dubilier

Proceedings of the National Academy of Sciences PNAS, doi/10.1073/pnas.1121198109

Max-Planck-Gesellschaft
Prebiotic evolution: Hairpins help each other out
The evolution of cells and organisms is thought to have been preceded by a phase in which informational molecules like DNA could be replicated selectively.
How to be a winner in the game of evolution
A new study by University of Arizona biologists helps explain why different groups of animals differ dramatically in their number of species, and how this is related to differences in their body forms and ways of life.
The galloping evolution in seahorses
A genome project, comprising six evolutionary biologists from Professor Axel Meyer's research team from Konstanz and researchers from China and Singapore, sequenced and analyzed the genome of the tiger tail seahorse.
Fast evolution affects everyone, everywhere
Rapid evolution of other species happens all around us all the time -- and many of the most extreme examples are associated with human influences.
Landscape evolution and hazards
Landscapes are formed by a combination of uplift and erosion.
New insight into enzyme evolution
How enzymes -- the biological proteins that act as catalysts and help complex reactions occur -- are 'tuned' to work at a particular temperature is described in new research from groups in New Zealand and the UK, including the University of Bristol.
The evolution of Dark-fly
On Nov. 11, 1954, Syuiti Mori turned out the lights on a small group of fruit flies.
A look into the evolution of the eye
A team of researchers, among them a zoologist from the University of Cologne, has succeeded in reconstructing a 160 million year old compound eye of a fossil crustacean found in southeastern France visible.
Is evolution more intelligent than we thought?
Evolution may be more intelligent than we thought, according to a University of Southampton professor.
The evolution of antievolution policies
Organized opposition to the teaching of evolution in public schoolsin the United States began in the 1920s, leading to the famous Scopes Monkey trial.

Best Science Podcasts 2017

We have hand picked the best science podcasts for 2017. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.

Now Playing: Radiolab

Truth Trolls
Today, a third story of folks relentlessly searching for the truth. But this time, the truth seekers are an unlikely bunch... internet trolls.


Now Playing: TED Radio Hour

Rethinking School
For most of modern history, humans have placed smaller humans in institutions called schools. But what parts of this model still work? And what must change? This hour, TED speakers rethink education.TED speakers include teacher Tyler DeWitt, social entrepreneur Sal Khan, international education expert Andreas Schleicher, and educator Linda Cliatt-Wayman.