Clostridia can synthesize catalytic nanoparticles in-situ at the zone of treatment. In essence, the microbial surface becomes the support for the catalyst, thus maintaining their high surface area. Concomitantly, microbes generate electron donors that cause reduction of contaminants. Current groundwater treatment technologies rely on delivering pre-formed catalytic nanoparticles into groundwater treatment zones and the addition of expensive molecular hydrogen to above ground pump and treat systems; two shortcomings that are overcome in this one-step process.