Phototrophic purple sulfur bacteria as heat engines in the South Andros Black Hole

TY - JOUR

T1 - Phototrophic purple sulfur bacteria as heat engines in the South Andros Black Hole

AU - Herbert, Rodney A.

AU - Gall, Andrew

AU - Maoka, Takashi

AU - Cogdell, Richard J.

AU - Robert, Bruno

AU - Takaichi, Shinichi

AU - Schwabe, Stephanie

PY - 2007

Y1 - 2007

N2 - 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 degrees 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.

AB - 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 degrees 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.

KW - Carotenoids

KW - Chromatiaceae

KW - Chromatography, High Pressure Liquid

KW - Light Signal Transduction

KW - Nuclear Magnetic Resonance, Biomolecular

KW - Photosynthesis

KW - Spectrometry, Fluorescence

KW - Temperature

U2 - 10.1007/s11120-007-9246-1

DO - 10.1007/s11120-007-9246-1

M3 - Article

C2 - 17906940

SN - 0166-8595

VL - 95

SP - 261

EP - 268

JO - Photosynthesis Research

JF - Photosynthesis Research

IS - 2-3

ER -