The grey "fleece" on the Pompeii worm's back is bacteria.
You’ve heard of those relationships in nature where organisms from different species benefit from living or working closely together. Bees and flowering plants, for example, depend on each other: The insects get food and the plants are pollinated. One of the world’s most unique examples of this phenomenon, known as symbiosis, is found at the bottom of the sea.
There, the Pompeii worm (Alvinella pompejana) lives at hydrothermal vents — geysers on the seafloor that spew super hot, mineral-rich water. Enduring wide-ranging temperatures from about 72 to 176 degrees Fahrenheit, the worm is the world’s most heat-tolerant animal. The worm also survives acidic water and conditions where sometimes there’s no oxygen at all, so its home is one of the planet’s most extreme environments.
Scientists trying to determine just how the worm tolerates the nearly boiling, toxic water have focused on the grey “fleece” of bacteria that live on the worm’s back. The bacteria live and feed on mucus produced by the worm but they also serve as a source of food and vitamins for the worm.
To learn more about this symbiotic relationship, researchers sequenced the bacteria’s genome, or studied their genes. The result, which was published Nov. 5 in the Proceedings of the National Academy of Sciences, is a catalog of everything the bacteria are capable of doing — from how they function to the nutrients they need to grow.
The project was led by University of Delaware Professor of Marine Biosciences Stephen Craig Cary and Alison Murray, a faculty member at the Desert Research Institute in Reno, Nev.
Cary is currently leading a research team that is exploring deep-sea hydrothermal vents in the Pacific Ocean as part of “Extreme 2008: A Deep-Sea Adventure.” To keep up with the expedition, go to the web site.
Collaborating on the project were Desert Research Institute faculty member Joseph Grzymski, UD Assistant Professor of Marine Biosciences Barbara Campbell, and Delaware Biotechnology Institute scientist Mihailo Kaplarevic. Also working on the project were UD Distinguished Professor of Electrical and Computer Engineering Guang Gao and researchers from the University of Waikato in Hamilton, New Zealand, and SymBio Corp. of San Jose, Calif.
So what can the bacteria do? A lot, it turns out. The scientists believe they can endure the same huge range of temperatures that the worms experience. They also can thrive in diverse chemical environments (hydrogen sulfide and heavy metals are common around the vents) and can process both oxygen and organic matter to make energy.
“In the hydrothermal vents there’s mixing between the hydrothermal fluids and the seawater and that mixing creates a very dynamic environment,” Campbell said.
But this wide range of traits doesn’t belong to just one type of bacteria. The researchers found that the organisms living on the worm’s back represent many closely related but diverse members from one strain of bacteria called Epsilonproteobacteria. The team believes that each type of bacteria is optimally adapted to specific temperature ranges and other conditions, allowing the community living on the worm’s back to thrive in the ever-changing, hostile ecosystem in which they live.
“Most symbioses in nature include one bacterium that is actually controlled and nurtured by the host, but in this situation we have many different types of bacteria,” Cary said. “That’s very unusual.”
Members of the research team discovered the Epsilonproteobacteria in the early ‘90s and have been working to understand them better ever since. That growing bank of knowledge could benefit an industry looking to develop a variety of products and applications, from new pharmaceuticals to enzymes capable of operating in hot, corrosive, high-pressure environments.
“This is probably one of the first studies to look at a symbiosis of this extreme environment and dissect it down to its bottom line, basically the recipe of success for these organisms,” Cary said. But the researchers have only just begun to describe what the bacteria can do.
For more about College of Marine and Earth Studies, visit www.ocean.udel.edu.