Bacterial Carbon Fixation in Dark Ocean Depths

Written by on September 8, 2011 in Marine Life, Technology
Ocean Layers

Image Credit: NOAA


By Henry Workman
Marine Science Today Writer

The biological process of carbon fixation plays indispensable roles at the primary level of ecosystems and in the world’s carbonic cycle.  Where there is sufficient sunlight to drive photosynthesis, the process by which plants convert CO2 into sugars and expel O2 as waste, energy passed through food chains originates from plant life.  However, in systems where light is scarce or absent, such as the aphotic zone of the ocean, the processes that convert carbon dioxide to a solid and more biologically useable form are less clearly understood.

It’s long been known that microscopic organisms are behind the biological integration of free CO2 at depths between 200 and 1000 meters (the mesopelagic zone), but the difficulty of obtaining reliable and representative samples from this level have made it difficult to determine the precise microbes and pathways responsible.  Certain strains within the taxonomic domain archaea, a kind of unicellular life form distinct from bacteria, have been previously implicated in deep water carbon fixation.  Measured levels of CO2 in the North Atlantic, though, have necessitated a search for other biological mechanisms.

New research published in the September 2 issue of AAAS’s Science details evidence of another key contributor to the ocean’s carbon equation.  State-of-the-art single cell sorting and DNA sequencing techniques were tested on mesopelagic bacterial plankton samples to map a genome of pervasive species.  Comparison and analysis confirmed the possibility of litho-autotrophic function, which means that these bacteria can make their own food in the absence of organic materials and sunlight.  CO2 molecules are integrated into the energy pathway by comprising structures that break down materials of mineral origin.  The samples of over 700 individual cells originated from two disparate regions of the ocean, a sign of how widespread these bacteria types are.

The study was an internationally cooperative effort from DOE JGI, Maine’s Bigelow Laboratory, MBARI, MIT, and the University of Vienna.

The discovery comes at a critical time in the context of related studies, supplementing ongoing research on the carbon cycle in the dark ocean.  Learning about carbon processing in the ocean’s largest biome, home to innumerable species, has potential applications in a diverse range of environmental fields of study concerned with the movement of carbon.


Copyright ©  2011 by Marine Science Today, a publication of OceanLines LLC

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