Abstract

The effects of extracellular polymeric substances (EPS) of Pseudomonas aeruginosa on adsorption and redox state alteration of dissolved As, Cr and U were investigated through batch experiments. Surfaces of bacterial cells were either vigorously washed or unwashed. Solutions of As(V), Cr(VI) and U(VI) were inoculated with the bacterial cells under no nutrient condition, and total aqueous concentrations and redox state alteration were monitored over time. No As adsorption occurred onto bacteria or EPS; however, unwashed bacteria reduced about 60% As(V) to As(III). Unwashed bacteria also led to removal of 45% total dissolved Cr and reduction of 64% Cr(VI). About
80% U(VI) was removed from solution with unwashed bacteria as well. Such electrochemical reduction of the elements was likely due to reducing capacity of EPS itself or detoxifying reduction of the bacteria which kept theirviability under protection of EPS. The results indicated that bacterial biofilm may significantly control the redox state and subsequent mobility of As, Cr and U in natural geologic settings.

Keywords bacteria, extracellular polymeric substances (EPS), arsenic, chromium, uranium