Biosorption of gold
occurs in a variety of organisms representing gram-positive
and gram-negative bacteria, archaea, fungi, and algae. Biological
removal of Au(III) from solution is often accompanied by reduction
of Au(III) to elemental gold (Au(0)). Some Fe(III)-reducing bacteria and archaea can reduce Au(III) to Au(0) using hydrogen
gas as an
electron donor. This reductive mechanism is thought to be enzymatically mediated and to be separate from Fe(III) reduction, as not all Fe(III)-reducing
organisms can also reduce Au(III) (Kashefi et al., 2001).
Isolated cell walls from Bacillus
subtilis collect granules of elemental gold when treated
with a solution of AuCl3 (Beveridge and Murray, 1976). While
of elemental gold most often occurs on the surface of the
organism, a study of the effects of different types of lipopolysaccharide
O-side chains on metal binding in Pseudomonas
aeruginosa found precipitated gold distributed randomly
throughout the cytoplasm and not accumulated at the cell surface
Reductive precipitation is not always required for microbial
gold accumulation. Bacillus cereus cells
were shown to bind gold particles from a suspension of colloidal gold in
what may be an ATP-dependent process (Ulberg et al., 1992).
A biological role for gold has been reported in Micrococcus
luteus. An NADH oxidase in M. luteus
Au(III) ions per active site was found to catalyze oxidation of methane to
(Levchenko et al., 2002).
For more information:
Medline for gold metabolism AND bacteria
Savvaidis I. Recovery of gold from thiourea solutions using
microorganisms. Biometals. 1998 Apr;11(2):145-51.
Pethkar AV, Kulkarni SK, Paknikar KM. Comparative studies
on metal biosorption by two strains of Cladosporium cladosporioides.
Technol. 2001 Dec;80(3):211-5.
Levchenko LA, Sadkov AP, Marakushev SA, Lariontseva NV.
Participation of biological membranes in colloidal gold transformation
by Micrococcus luteus cells. Membr
Cell Biol. 1997;11(1):131-5.