New research on sulfate-reducing bacteria may offer good news for bioremediation efforts to clean up acid mine drainages and other environments with high levels of harmful metals.

Sulfate-reducing bacteria is known to extract metal dissolved in anoxic waters and by isolating it into nanoscale particles. But, the tiny size of these particles (2-6 nm) makes them highly mobile and under the right conditions they can quickly redissolve.

Previous research work showed that some organics can promote aggregation of the nanoparticles which induces settling and thus decreased their solubility. John Moreau and colleagues hypothesized that natural organic matter contributes to the formation of densely aggregated nanoparticulate zinc sulfide (ZnS) spheroids.

The research team studied biofilms of sulfate-reducing bacteria collected from a flooded lead and zinc mine in Wisconsin. They report that metal-sulfide nanoparticles produced by these bacteria form aggregates that contain trapped metal-binding polypeptides and proteins, keeping the particles stuck within the biofilm and limiting their dispersion in the environment.

The research is published in June 15 issue of Science – “Extracellular Proteins Limit the Dispersal of Biogenic Nanoparticles”.