An X-ray Absorption Fine Structure study of Au adsorbed onto the non-metabolizing cells of two soil bacterial species

Journal Article · Mon Feb 09 04:00:00 EST 2015 · Geochim. Cosmochim. Acta

DOI:https://doi.org/10.1016/j.gca.2012.02.030· OSTI ID:1043734

Song, Zhen; Kenney, Janice P.L.; Fein, Jeremy B.; Bunker, Bruce A. ^[1]

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1. Notre

Gram-positive and Gram-negative bacterial cells can remove Au from Au(III)-chloride solutions, and the extent of removal is strongly pH dependent. In order to determine the removal mechanisms, X-ray Absorption Fine Structure (XAFS) spectroscopy experiments were conducted on non-metabolizing biomass of Bacillus subtilis and Pseudomonas putida with fixed Au(III) concentrations over a range of bacterial concentrations and pH values. X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) data on both bacterial species indicate that more than 90% of the Au atoms on the bacterial cell walls were reduced to Au(I). In contrast to what has been observed for Au(III) interaction with metabolizing bacterial cells, no Au(0) or Au-Au nearest neighbors were observed in our experimental systems. All of the removed Au was present as adsorbed bacterial surface complexes. For both species, the XAFS data suggest that although Au-chloride-hydroxide aqueous complexes dominate the speciation of Au in solution, Au on the bacterial cell wall is characterized predominantly by binding of Au atoms to sulfhydryl functional groups and amine and/or carboxyl functional groups, and the relative importance of the sulfhydryl groups increases with increasing pH and with decreasing Au loading. The XAFS data for both microorganism species suggest that adsorption is the first step in the formation of Au nanoparticles by bacteria, and the results enhance our ability to account for the behavior of Au in bacteria-bearing geologic systems.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: NSF
• OSTI ID: 1043734
• Journal Information: Geochim. Cosmochim. Acta, Journal Name: Geochim. Cosmochim. Acta Journal Issue: 06, 2012 Vol. 86; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ABSORPTION SPECTROSCOPY
ADSORPTION
AMINES
ATOMS
BACILLUS SUBTILIS
BACTERIA
BIOMASS
CELL WALL
FINE STRUCTURE
GOLD
GOLD CHLORIDES
MICROORGANISMS
PH VALUE
PSEUDOMONAS
REMOVAL
SOILS
X-RAY SPECTROSCOPY