Extracellular iron-sulfur precipitates from growth of desulfovibrio desulfuricans

摘要

We have examined extracellular iron-bearing precipitates resulting from the growth of Desulfovibrio desulfuricans in a basal medium with lactate as the carbon source and ferrous sulfate. Black precipitates were obtained when D. desulfuricans was grown with an excess of FeSO{sub}4. When D. desulfuricans was grown under conditions with low amounts of FeSO{sub}4, brown precipitates were obtained. The precipitates were characterized by iron K-edge XAFS (X-ray absorption fine structure), {left sup}57Fe Mossbauer-effect spectroscopy, and powder X-ray diffraction. Both were noncrystalline and nonmagnetic (at room temperature) solids containing high-spin Fe(III). The spectroscopic data for the black precipitates indicate the formation of an iron-sulfur phase with 6 nearest S neighbors about Fe at an average distance of 2.24(1) A, whereas the brown precipitates are an iron-oxygen-sulfur phase with 6 nearest O neighbors about Fe at an average distance of 1.95(1) A.