Structural and Chemical characterisation of placer gold grains: Implications for bacterial contributions to grain formation

Shuster, Jeremiah, Johnston, Chad W., Magarvey, Nathan A., Gordon, Robert A., Barron, Keith, Banerjee, Neil and Southam, Gordon (2015) Structural and Chemical characterisation of placer gold grains: Implications for bacterial contributions to grain formation. Geomicrobiology Journal, 32 5: 158-169. doi:10.1080/01490451.2014.935534


Author Shuster, Jeremiah
Johnston, Chad W.
Magarvey, Nathan A.
Gordon, Robert A.
Barron, Keith
Banerjee, Neil
Southam, Gordon
Title Structural and Chemical characterisation of placer gold grains: Implications for bacterial contributions to grain formation
Journal name Geomicrobiology Journal   Check publisher's open access policy
ISSN 0149-0451
1521-0529
Publication date 2015
Year available 2014
Sub-type Article (original research)
DOI 10.1080/01490451.2014.935534
Open Access Status
Volume 32
Issue 5
Start page 158
End page 169
Total pages 12
Place of publication Philadelphia, PA United States
Publisher Taylor and Francis
Collection year 2015
Language eng
Formatted abstract
Gold grains collected from the Rio Saldaña River, Colombia were hundred's of micrometers in size and discoid-ellipse in shape. Fourteen of 63 grains contained an iron oxyhydroxide coating that occurred as ca. 50 to 100 nm thick lamina while thicker coatings were comprised of colloids 200 nm to 4 μm in diameter. Bacterial-size casts were observed throughout the thicker iron oxyhydroxide coating and intuitively represent relic impressions of bacterial cells. The surface textures of gold grains were generally smooth with surficial depressions or crevices containing detrital material colonised by bacteria. Focus Ion Beam (FIB) milled cross-sections demonstrated that the detrital material contained nanophase gold particles. Biofilm attached to this detrital material contained ca. 2 to 3 nm colloidal gold attached to exopolymeric substances. Cross sections of grains revealed solid cores with vesicular voids near the grain edge including a bacterial-size cast interpreted to be a permineralised bacterial cell. Synchrotron-based elemental mapping indicated that grains contained heterogenously distributed Ag and Cu. While strong Ag and Cu signals (relative to Au) were detected in the core, a stronger Au signal occurred at the edge of grains demonstrating enriched rims of secondary gold. The preservation of bacterial casts and biofilms associated with secondary gold structures at the surface of grains suggest that bacteria may contribute to gold enrichment and growth in this placer environment. Bacteria, occurring on the surface of 13 of 25 gold grains, were enriched by “inoculating” individual grains into separate test tubes containing R2B growth medium. Enriched growth of bacteria on gold grain surfaces demonstrated preferential attachment onto detrital material within creviced regions. The dominant bacteria from these enrichments were transferred to solid R2A medium to obtain pure isolates. The isolates were identified as one of four bacterial species: Nitrobacter sp. 263, Shewanella sp. YM-8, Sediminibacterium sp. B2-10-2 and sp. I-32 based on 16S ribosomal DNA sequencing.
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ
Additional Notes Published online: 10 Dec 2014

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Earth Sciences Publications
Official 2015 Collection
 
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Created: Mon, 18 Aug 2014, 11:14:32 EST by Ashleigh Paroz on behalf of School of Earth Sciences