Originally,
scientists assumed that organisms living at deep-sea hydrothermal vents
received nutrients by way of organic compound intake through cell walls and
micro-tentacles. After the discovery and study of Rifitia Pachyptila in 1971 at the Galapagos Rift, scientists began
to see that a new form of energy synthesis was really occurring at these
deep-sea vents, a synthesis referred to as chemosynthesis. Chemosynthesis is
the synthesis of organic compounds from inorganic compounds such as CO2, using
chemicals like hydrogen sulfide in lieu of light energy (photosynthesis). Scientists soon discovered that many of
the organisms living at deep-sea vents actually obtained nutrients through
endosynthetic bacteria, a form of chemolithoautotrophy. These bacteria utilize
reduced sulfur compounds from vents as electron donors., synthesizing organic
compounds that can be passed to a host. The authors observe that this
phenomenon occurs not only at deep-sea vents, but also in an array of habitats
worldwide. They describe the incredible diversity of hosts, habitats, and
symbionts, concluding that many genetic similarities and differences exist
within the groups of chemosynthetic bacteria. Hosts and symbionts have adapted
to each other, creating the possibility for genetic exchange between the
partners. In general, environments are conducive to chemosynthetic behavior
when the sulfide concentrations are high. By observing organisms with reduced
digestive systems, scientists can trace host lineages. Many different lineages
of bacteria can establish chemosynthetic symbioses. The discovery not only
supports theories of evolution, but also changes the way scientists approach
symbiotic behavior in organisms.
In observing the diversity of ocean
habitats, scientists are able to relate hosts to symbionts, allowing for
unlimited research and discovery related to energy-synthesizing organisms and
deep-sea hydrothermal vents, cold seeps, wood falls, coastal sediments, and
continental margins.
Hydrothermal vents are fissures in
the ocean surface from which heated water issues. These vents are found along
volcanic rifts and hot spots at the earths surface, and are a result of
tectonic plate movement. These vent areas are productive in terms of sustaining
life and providing for energy synthesis. Deep-sea vents and cold seeps often
provide for symbiotic behavior between endosymbiotic bacteria and their hosts.
Typically forming along active ridges, chemosynthetic environments allow for
the conversion of carbon molecules (CO2) into organic compounds by way of oxidation.
Chemosynthesis allows for sustained forms of life in deep and shallow parts of
the marine environment. The discovery of this marine activity dates back to
1971 at the Galapagos Rift, where scientists took samples of tubeworms,
revealing a sustained form of life that is not dependent on light energy.
Autotrophs, organisms that assemble inorganic molecules into organic molecules
by way of chemical reactions, exist because of the release of gases through
hydrothermal vents and the chemical reactions of inorganic carbon with hydrogen
sulfide. In general, vents in the ocean floor allow for not only the existence
of life beneath the reach of the suns light, but also symbiotic patterns that
further evolution and worldwide host-symbiont relationships.
-Yates Webb
Symbiotic Diversity in Marine Animals: The Art of Harnessing Chemosynthesis
Nicole Dubilier, Claudia Bergin, Christian Lott
Nature Reviews Microbiology
October 1, 2008