Minic, Zoran. Organisms of deep sea hydrothermal vents as a source for studying adaptation and evolution. Symbiosis 47.3 (2009): 121-132.

Deep sea hydrothermal vents provide a habitat that is derived of sunlight, has extremely high pressure, and the only source of heat comes from the deep sea vents. What adaptations have organisms such as Riftia pachyptila evolved to be able to survive in such an environment?

Riftia pachyptila live in an extremely hostile, unstable environment. Riftia pachyptila are able to survive these conditions through the help of chemoautotrophic bacterial symbionts that live within the worms' trophosome. This symbiosis has resulted in an obligate mutualism between the two organisms; they are unable to survive without one another.

The author looked at the metabolic pathways that Riftia pachyptila and its endosymbionts share. There are a lot of different metabolic pathways, but one of the most important pathways includes the ability for the bacteria to produce enzymes, such as nitrate reductase, that Riftia pachyptila are unable to produce. Nitrate reductase is an enzyme that is important for nitrogen assimilation, and the general absence of this enzyme would normally result in the death of the organism. This indicates that Riftia pachyptila is dependent on its bacteria symbionts for the biosynthesis of usable nitrogen molecules.

The symbiotic relationship between Riftia pachyptila and its intracellular bacteria are the reason that the tube worm is able to survive in the harsh conditions of hydrothermal vents. Without the bacteria, Riftia pachyptila would not be able produce the proper enzymes that enable it to utilize the molecules in its environment, and would then be unable to survive.

(248 words)

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(posted Dec. 24, 2015)