Marine worm with a toxic diet
23 Apr 2012 by Evoluted New Media
Faced with a scarce food supply in the sandy sediments in which it lives, a small marine worm survives on a highly poisonous menu of carbon monoxide and hydrogen sulphide.
The worm – Olavius algarvensis – thrives on these poisons thanks to millions of symbiotic bacteria that live under its skin, which use the energy from carbon monoxide and hydrogen sulphide to produce food for the worm.
“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,” said Nicole Dubilier, Head of Symbiosis Group at the Max Planck Institute for Marine Microbiology.
Some of the symbiotic bacteria in the worm can take up hydrogen and organic nutrients from the environment – even if present in small amounts. They can also recycle the worm’s waste, which still contains lots of energy for their own purposes.
“This is the reason why the worm has been able to not only reduce its digestive system, but also its kidney-like excretory organs,” said Dubilier, “Something that has not been discovered in any other marine animal.”
The research – which includes Greifswald University – used a combination of cutting-edge techniques such as metaproteomics and metabolomics. This made it possible to analyse a large proportion of proteins and metabolic products in the organism.
“Using metaproteomics, we were able to identify thousands of proteins and assign them to the individual partners in the symbiosis,” said Thomas Schweder from Greifswald’s Institute of Pharmacy. “This gave us direct insights into the metabolism of the bacterial symbionts and their interactions with the host.”
The researchers were surprised that their analyses revealed that the worm has large amounts of proteins that allow it to use carbon monoxide as an energy source, because it is so poisonous.
It is only recently that the researchers – who have published their work in Proceedings of the National Academy of Sciences – have been able to work out the worm’s metabolic pathways and discover new energy sources.
“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,” said Dubilier. “And seemingly these modest worms are an excellent model for a better understanding of other complex symbioses, such as those of the human gut.”
