Nanocrystalline Nickel and Cobalt Sulfides Formed by a Heavy Metal-Tolerant, Sulfate-Reducing Enrichment Culture

Abstract

A soil enrichment culture of the sulfate-reducers Desulfosporosinus auripigmenti and Citrobacter freundii and of fermentative bacteria from a former uranium-mining site was studied for its metal retention potential by promoting metal sulfide precipitation. The culture could tolerate up to 30 mM Ni and 40 mM Co. XRD and TEM analyses revealed the formation of amorphous NiS together with nanocrystalline, metastable α-NiS, and nanocrystalline cobalt pentlandite. The α-NiS with a grain size of 5 nm shows probably an example of size-dependent phase stability and/or specific biomineralization precipitation paths. Detailed mineralogical characterizations are necessary to correctly assess the mineral inventory and thus metal bioavailability.

Keywords:

• sulfate reduction
• metal sulfides
• nanocrystals
• heavy metal tolerance

Acknowledgments

The authors are thankful to Dirk Merten for ICP-MS and ICP-OES measurements and to Olivia Rasigraf for technical assistance. This project was part of the graduate research school, “Alteration and element mobility at the microbe-mineral interface,” financially supported by the German Research Foundation DFG (1257), and is embedded in the Jena School of Microbial Communication (JSMC). Kilian Pollok was supported by Grant 03G0718A from the R&D-Programme GEOTECHNOLOGIEN, funded by the German Ministry of Education and Research (BMBF) (publication no. GEOTECH- 1949). Falko Langenhorst gratefully acknowledges financial support by the Leibniz programme of the Deutsche Forschungsgemeinschaft (LA 830/14-1).