Monday, April 11, 2011

Pompeii Worms and Proteobacteria: Voted Hottest Couple

In high school there's always one couple that seems so perfectly matched, like the typical star quarterback and head cheerleader relationship. He carries her heavy books to class and she brings him ice cold water to practice. These types of people win prom king and queen in every cliche movie and will inevitably live happily ever after. The natural world also has its own superlative categories. Alvinella pompejana, commonly referred to as the Pompeii worm, is an extremophile polychaete that resides in the East Pacific Rise hydrothermal vents deep in the Pacific Ocean [1]. In this environment, temperatures can be as hot as 176ยบ F and the five inch worm is still able to survive [2]. It is the most heat tolerant animal and can have a broad temperature gradient along its body. Tentacle-like gills adorn the A. pompejana's head as if to crown itself with the title "hottest creature on earth." Despite the Pompeii worm's adaptations to extreme environments, thermal vents are unstable habitats so the worms are probably inclined towards methods of dispersal with large numbers of offspring. However, like most deep sea vent creatures, the full life cycle of the Pompeii worm remains unknown [3].


Pompeii worms insert their tails into the side of the vents, leaving their head exposed to the milder waters of 72°F [5]. How is the worm able to tolerate such a range of temperatures? The secret lies in a fuzzy hairs along the Pompeii worm's body. The "fleece" is actually bacteria.

Colonies of filamentous Proteobacteria form a protective coating over the worm's mucus glands [7]. It's not quite a letterman's jacket that the previously mentioned football star would give his cheerleader girlfriend. In fact, it's a more profound mutualistic relationship.

Description of Relationship:
The bacteria and A. pompejana are protected from the extreme heat by enzymes in the epibacteria. Some research indicates that the bacteria serves as thermal insulation [1]. In return, the Pompeii worm secretes a mucus that the bacteria lives and feeds upon [3]. This relationship has evolved to a level of morphological functionality. The bacteria and the mucosal secretions are part of the worm and contribute to protecting it from the vent temperatures [3]. Metabolic processes for the worm may also depend on the bacteria because of the extreme conditions in their habitat. The bacteria can transform inorganic substances into usable sources of energy, and thus helping the worm survive nutritionally as well.

Cost/Benefit Analysis:
Both organisms benefit from the other, the worm gains protection and sources of energy, while the bacteria gains a place to live and sustenance (Pompeii worm mucus). The worm encourages bacteria attachment by secreting the mucus, so the costs of housing the worm are outweighed by benefits. Diversity of life in the hydrothermal vents is very small, due to the lack of organismal adaptations to such conditions. Extremophile bacteria's reliance on the Pompeii worm is purely beneficial.



  1. In some mutualistic relationships the two organisms cannot survive without each other, is that the case with these two organisms? Can the pompeii worm and the bacteria live freely or have the same relationship with another organism? Also what in the bacteria allows it to withstand the heat of the hydrothermal vents in order to protect the pompeii worm?

  2. The Wolbachia bacteria is seen having multiple mutualistic/parasitic relationships with multiple species. Does this type of bacteria have additional mutualistic/parasitic relationships with other species? Does this bacteria thrive outside the hydrothermal vents in differing ecosystems like the wolbachia bacteria?

  3. Meagan: The worm and bacteria are not completely dependent upon each other. It is still unknown as to how the Pompeii worm is able to survive in the hydrothermal vents. Scientists try to bring live worms up from the vents to study them, but they die because of the pressure changes. There is some research that supports the evidence that the worms can live independently. Since few organisms can live in the vents, the bacteria and worm formed a relationship that was convenient and beneficial.

    Stephanie: The bacteria can probably have other relationships. Since it is an extremophile bacteria, it is found in the hotter environments with temperatures similar to the vents. Any other organism that is able to withstand the heat, can probably form a relationship with the bacteria.