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An Energy Balance Model to Predict Chemical Partitioning in a Photosynthetic Microbial MatStudies of biosignature formation in photosynthetic microbial mat communities offer potentially useful insights with regards to both solar and extrasolar astrobiology. Biosignature formation in such systems results from the chemical transformation of photosynthetically fixed carbon by accessory microorganisms. This fixed carbon represents a source not only of reducing power, but also energy, to these organisms, so that chemical and energy budgets should be coupled. We tested this hypothesis by applying an energy balance model to predict the fate of photosynthetic productivity under dark, anoxic conditions. Fermentation of photosynthetically fixed carbon is taken to be the only source of energy available to cyanobacteria in the absence of light and oxygen, and nitrogen fixation is the principal energy demand. The alternate fate for fixed carbon is to build cyanobacterial biomass with Redfield C:N ratio. The model predicts that, under completely nitrogen-limited conditions, growth is optimized when 78% of fixed carbon stores are directed into fermentative energy generation, with the remainder allocated to growth. These predictions were compared to measurements made on microbial mats that are known to be both nitrogen-limited and populated by actively nitrogen-fixing cyanobacteria. In these mats, under dark, anoxic conditions, 82% of fixed carbon stores were diverted into fermentation. The close agreement between these independent approaches suggests that energy balance models may provide a quantitative means of predicting chemical partitioning within such systems - an important step towards understanding how biological productivity is ultimately partitioned into biosignature compounds.
Document ID
20060046373
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Hoehler, Tori M.
(NASA Ames Research Center Moffett Field, CA, United States)
Albert, Daniel B.
(North Carolina Univ. NC, United States)
DesMarais, David J.
(NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
August 23, 2013
Publication Date
January 1, 2006
Subject Category
Exobiology
Meeting Information
Meeting: AbSciCon 2006
Location: Washington, DC
Country: United States
Start Date: March 26, 2006
Funding Number(s)
OTHER: 21-344-58-00
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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