Palladium has no know biological function and palladium compounds are toxic to both prokaryotic and eukaryotic cells (Khan et al, 1991). Palladium is a precious metal of industrial importance, and biological methods to recover palladium from solution have been explored, as chemical recovery methods are inefficient. Desulfovibrio desulfuricans was found to reduce Pd(II) to Pd(0) using formate or H₂ as an electron donor, with concomitant accumulation of the reduced metal on cell surfaces (Lloyd et al, 2002). The authors propose that D. desulfuricans reduces palladium enzymatically. D. desulfuricans resting cells and biomass from other organisms have been evaluated as biosorbents to passively remove soluble palladium from solution (Yong et al, 2002; Remoudaki et al, 1999). The transfer of a methyl group to palladium from the vitamin B₁₂ derivative methylcobablamin has been reported in vitro, but the methylated palladium species was not stable (Scovell, 1974).

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Remoudaki E, Tsezos M, Hatzikioseyian A, Karakoussis Y. Mechanism of palladium biosorption by microbial biomass. The effects of metal ionic speciation and solution co-ions. Process Metallurgy 1999;9B:449-62.

Scovell WH. Kinetics and mechanism of methyl transfer from methylcobalamin to palladium(II). J Am Chem Soc. 1974;96: 3451-56.

Yong P, Rowson NA, Farr JPG, Harris IR, Macaskie LE. Bioaccumulation of palladium by Desulfovibrio desulfuricans. J Chem Technol Biotechnol. 2002;77:593-601.