HR: 0830h
AN: OS31C-0221    [PDF]
TI: The Potential Importance of Metal-Sulfide Complexes in the Ancient Ocean on Cyanobacterial Metal Requirements
AU: * Saito, M A
EM: mak@whoi.edu
AF: Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543 United States
AU: Sigman, D M
EM: sigman@princeton.edu
AF: Department of Geosciences, Princeton University, Princeton, NJ 08544 United States
AU: Morel, F M
EM: morel@princeton.edu
AF: Department of Geosciences, Princeton University, Princeton, NJ 08544 United States
AB: Recent evidence from the sulfur isotopic record indicates a transition ~2.5 billion years ago from an ocean chemistry first dominated by iron and then by sulfide. It has been hypothesized that the selection of metal centers in metalloenzymes has been influenced by the availability of metals through geological time, in particular as a result of large differences in the solubility of metals-sulfides. In this study, we examine the trace metal requirements and sensitivities of marine cyanobacteria and use recent stability constants to model the abundance and chemical speciation of metals across this chemical transition ~2.5 billion years ago. Two major results are reported here: 1) the marine cyanobacterial species studied thus far show trace metal preferences and sensitivities that are consistent with their evolution in a sulfidic marine environment; 2) in an ancient ocean dominated by high fluxes and concentrations of iron, the relative availability of trace metals would have been similar to that of a sulfidic system (Fe$>$Mn,Ni,Co$>$$>$Cd,Zn,Cu) as a result of the formation of dissolved sulfide complexes. Thus the formation of strong aqueous metal-sulfide complexes was likely as important as the precipitation of minerals in influencing the selection of metals in biology. These results suggest that marine biogeochemical cycles and marine bioinorganic chemistry have co-evolved, and that the evidence for this co-evolution has been preserved in the physiology and genomes of modern descendants of the early cyanobacteria.
DE: 4805 Biogeochemical cycles (1615)
DE: 4807 Chemical speciation and complexation
DE: 4835 Inorganic marine chemistry
DE: 4875 Trace elements
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting