Growth of sulfate-reducing bacteria with solid-phase electron acceptors.

Area of Science:

• Geochemistry
• Microbiology
• Environmental Science

Background:

• Sulfate-reducing bacteria (SRB) are crucial in biogeochemical cycles.
• The electron acceptor capabilities of low-solubility sulfates are not fully understood.
• Minerals like hannebachite and gypsum are byproducts of industrial processes.

Purpose of the Study:

• To investigate the potential of SRB to use crystalline sulfates (hannebachite, gypsum, anglesite, barite) as electron acceptors.
• To monitor bacterial growth and sulfide production using these minerals.
• To understand the implications for lead speciation and biogeochemical cycling.

Main Methods:

• Culturing SRB with lactate as the electron donor and four different solid-phase sulfates as electron acceptors.
• Monitoring bacterial growth via protein measurements.
• Quantifying biogenic sulfide (H2S and HS-) formation.
• Analyzing solid precipitates using techniques like X-ray diffraction (XRD) for galena (PbS).

Main Results:

• Biogenic sulfide formation and bacterial growth were observed with all tested sulfate minerals.
• Gypsum showed high reactivity, comparable to soluble sulfates.
• Hannebachite reduction was slower, while barite supported minimal growth.
• Anglesite reduction led to galena precipitation, indicating lead immobilization.

Conclusions:

• Low-solubility crystalline sulfates are biologically reactive electron acceptors for SRB under reducing conditions.
• SRB activity influences the speciation of metals like lead through precipitation of sulfides (e.g., galena).
• This study highlights the interconnected roles of anaerobic and aerobic microbes in the cycling of solid-phase sulfates and sulfides.