Se-Bearing Colloidal Particles Produced by Sulfate-Reducing Bacteria and Sulfide-Oxidizing Bacteria: TEM StudyReport as inadecuate




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As determined by transmission electron microscopy TEM, the reduction of selenate and selenite by Desulfovibrio desulfuricans, a sulfate-reducing bacterium, produces spherical Se, S sub-micro particles outside the cell. The particles are crystalline or amorphous, depending on medium composition. Amorphous-like Se-rich spherical particles may also occur inside the bacterial cells. The bacteria are more active in the reduction of selenite than selenate. The Desulfovibrio desulfuricans bacterium is able to extract S in the S, Se solid solution particles and transform S-rich particles into Se-rich and Se crystals. Photoautotrophs, such as Chromatium spp., are able to oxidize sulfide S2-. When the bacteria grow in sulfide- and selenide-bearing environments, they produce amorphous-like S, Se globules inside the cells. TEM results show that compositional zonation in the S, Se globules occur in Chromatium spp. collected from a top sediment layer of a Se-contaminated pond. S2- may be from the products of sulfate-reducing bacteria. Both the sulfate-reducing bacteria and photosynthetic Chromatium metabolize S preferentially over Se. It is proposed that the S-rich zones are formed during photosynthesis day period, and the Se-rich zones are formed during respiration active night period. The results indicate that both Desulfovibrio desulfuricans and Chromatium spp. are able to immobilize the oxidized selenium selenate and-or selenite in the forms of elemental selenium and Se, S solid solutions. The bacteria reduce S in the Se, S particles and further enrich Se in the crystalline particles. The reduced S combines with Fe2+ to form amorphous FeS.

KEYWORDS

Selenium; Sulfate-Reducing Bacteria; Sulfide-Oxidizing Bacteria; Transmission Electron Microscopy

Cite this paper

H. Xu and L. Barton -Se-Bearing Colloidal Particles Produced by Sulfate-Reducing Bacteria and Sulfide-Oxidizing Bacteria: TEM Study,- Advances in Microbiology, Vol. 3 No. 2, 2013, pp. 205-211. doi: 10.4236-aim.2013.32031.





Author: Huifang Xu, Larry L. Barton

Source: http://www.scirp.org/



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