<i>Clostridium</i>Species as Metallic Copper-Forming Bacteria in Soil under Reducing Conditions

Abstract

Recent studies have reported the formation of Cu0 nanoparticles (CuNP) by suspended bacteria in pore water of periodically flooded soils, but the bacteria have not yet been identified. The aim of this study was to identify the CuNP-forming bacteria and to determine the location of CuNP formation relative to the bacterial cell surface. Electron microscopy revealed that the bacteria were rod-shaped spore formers and suggested that CuNP were formed in the periplasm. Combined results from denaturing gradient gel electrophoresis, 16S rRNA gene clone libraries, and classic microbiological cultivation techniques provided strong evidence for a Clostridium sp. strain as the CuNP-forming bacteria. Clostridia are well-adapted to frequent flooding and drying due to their ability to form spores and may play an important role in Cu cycling and metallic Cu formation in redox-dynamic environments.