Extracellular metal-binding activity of the sulphate-reducing bacterium Desulfococcus multivorans

Polarography was used to measure the copper-binding ability of culture filtrates from a range of sulphate-reducing bacteria (SRB), including pure cultures and environmental isolates. Of those tested, Desulfococcus multivorans was shown to have the greatest copper-binding capacity and this organism was used for further experiments. Extracellular copper- and zinc-binding activities of Dc. multivorans culture filtrates from batch cultures increased over time and reached a maximum after 10 d growth. The culture filtrate was shown to bind copper reversibly and zinc irreversibly. Twelve-day-old Dc. multivorans culture filtrates were shown to have a copper-binding capacity of 3.64 ± 0.33 μmol ml^-1 with a stability constant, log₁₀K, of 5.68 ± 0.64 (n = 4). The metal-binding compound was partially purified from culture growth media by dichloromethane extraction followed by HPLC using an acetonitrile gradient.