HR: 08:00h
AN: B31D-01 INVITED     [Abstracts]
TI: Biosynthetic Pathways, Gene Replacement and the Antiquity of Life
AU: * Blankenship, R
EM: blankenship@asu.edu
AF: Arizona State University, Department of Chemistry and Biochemistry , Tempe, AZ 85287-1604 United States
AU: Raymond, J
EM: raymond20@llnl.gov
AF: Lawrence Livermore National Laboratory, Biology and Biotechnology Research Program, Livermore, CA 94551 United States
AB: Our understanding of the evolution and diversity of life during the Archean has been profoundly influenced by geological signatures including microfossils, stromatolites, and fractionated carbon and sulfur isotopes. These biosignatures have been extensively debated on the grounds of competing abiotic processes. Hopane and squalene biomarkers have been taken as evidence that by 2700 Ma, all three domains of life had emerged, that cyanobacteria, the `inventors' of oxygenic photosynthesis, had diverged from their bacterial ancestors, heralding the impending oxidation of Earth's atmosphere, and that O2 was already available, as it is required explicitly in modern organisms for the synthesis of squalene. We argue that, based on corollaries present throughout enzymology, the oxidization of squalene during the Archean could just as likely have been carried out by an anaerobic enzyme that either remains to be characterized or that may have been totally lost as eukaryotes assumed primarily aerobic lifestyles. The transition from an anoxic to an oxic world had unfathomable consequences for early life; molecular oxygen and its derivatives went from being poisonous in an obligately anaerobic world, to assuming a central role in the subsequent development of complex, macroscopic life. Though the aftermath was global in scale, the biological transition to aerobiosis was effected at the molecular level, which included the evolution of a wealth of new enzymes, the extensive modification of many existing enzymes, and the `rewiring' of central biochemical pathways.
DE: 0325 Evolution of the atmosphere
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting