Formation of Sphalerite (ZnS) Deposits in Natural Biofilms of Sulfate-Reducing Bacteria

TLDR

Micrometer‑scale sphalerite aggregates form within natural biofilms dominated by aerotolerant sulfate‑reducing Desulfobacteriaceae. Sphalerite precipitation buffers low sulfide concentrations, yielding an almost monomineralic product. The biofilm concentrates zinc up to a million‑fold over groundwater and also enriches arsenic and selenium, demonstrating microbial control of metal concentrations and suggesting biological pathways for low‑temperature ZnS deposits.

Abstract

Abundant, micrometer-scale, spherical aggregates of 2- to 5-nanometer-diameter sphalerite (ZnS) particles formed within natural biofilms dominated by relatively aerotolerant sulfate-reducing bacteria of the family Desulfobacteriaceae. The biofilm zinc concentration is about 10 6 times that of associated groundwater (0.09 to 1.1 parts per million zinc). Sphalerite also concentrates arsenic (0.01 weight %) and selenium (0.004 weight %). The almost monomineralic product results from buffering of sulfide concentrations at low values by sphalerite precipitation. These results show how microbes control metal concentrations in groundwater- and wetland-based remediation systems and suggest biological routes for formation of some low-temperature ZnS deposits.