Phototrophic purple sulfur bacteria as heat engines in the South Andros Black Hole |
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Authors: | Rodney A Herbert Andrew Gall Takashi Maoka Richard J Cogdell Bruno Robert Shinichi Takaichi Stephanie Schwabe |
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Institution: | (1) Division of Environmental and Applied Biology, School of Life Sciences, University of Dundee, Dundee, DD1 4HN, UK;(2) Institut de Biologie et Technologies de Saclay, Commissariat à l’Energie Atomique, Gif sur Yvette, 91191, France;(3) Research Institute for Production Development, Shinogamo-morimoto-cho, Sakyou-ku Kyoto, 606-0805, Japan;(4) Institute of Biomedical and Life Sciences, University of Glasgow, Biomedical Research Building, Glasgow, G12 8TA, UK;(5) Biological Laboratory, Nippon Medical School, Nakahara Kawasaki, 211-0063, Japan;(6) International Blue Holes Foundation, 5 Longitude Lane, Charleston, SC 29401, USA |
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Abstract: | Photosynthetic organisms normally endeavor to optimize the efficiency of their light-harvesting apparatus. However, here we
describe two bacterial isolates belonging to the genera Allochromatium and Thiocapsa that demonstrate a novel adaptation by optimizing their external growth conditions at the expense of photosynthetic efficiency.
In the South Andros Black Hole, Bahamas, a dense l-m thick layer of these anoxygenic purple sulfur bacteria is present at
a depth of 17.8 m. In this layer the water temperature increases sharply to 36°C as a consequence of the low-energy transfer
efficiency of their carotenoids (ca. 30%). These include spirilloxanthin, and related polyene molecules and a novel chiral
carotenoid identified as spirilloxanthin-2-ol, not previously reported in purple bacteria. To our knowledge, this study presents
the first evidence of such a bacterial mass significantly increasing the ambient water temperature. The transduction of light
to heat energy to excess heat may provide these anoxygenic phototropic bacteria with a competitive advantage over non-thermotolerant
species, which would account for their predominance within the microbial layer.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Anoxygenic purple sulfur bacteria Allochromatium Thiocapsa South Andros Black Hole Carotenoid Spirilloxanthin Energy-transfer |
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