Bacterial deposition of gold on hair: archeological, forensic and toxicological implications.
BACKGROUND
Trace metal analyses in hair are used in archeological, forensic and toxicological investigations as proxies for metabolic processes. We show metallophilic bacteria mediating the deposition of gold (Au), used as tracer for microbial activity in hair post mortem after burial, affecting results of such analyses.


RESULTS
Human hair was incubated for up to six months in auriferous soils, in natural soil columns (Experiment 1), soils amended with mobile Au(III)-complexes (Experiment 2) and the Au-precipitating bacterium Cupriavidus metallidurans (Experiment 3), in peptone-meat-extract (PME) medium in a culture of C. metallidurans amended with Au(III)-complexes (Experiment 4), and in non-auriferous soil (Experiment 5). Hair samples were analyzed using scanning electron microscopy, confocal microscopy and inductively coupled plasma-mass spectrometry. In Experiments 1-4 the Au content increased with time (P = 0.038). The largest increase was observed in Experiment 4 vs. Experiment 1 (mean = 1188 vs. 161 microg kg(-1), Fisher's least significance 0.001). The sulfur content, a proxy for hair metabolism, remained unchanged. Notably, the ratios of Au-to-S increased with time (linear trend P = 0.02) and with added Au and bacteria (linear trend, P = 0.005), demonstrating that larger populations of Au-precipitating bacteria and increased availability of Au increased the deposition of Au on the hair.


CONCLUSIONS
Interactions of soil biota with hair post mortem may distort results of hair analyses, implying that metal content, microbial activities and the duration of burial must be considered in the interpretation of results of archeological, forensic and toxicological hair analyses, which have hitherto been proxies for pre-mortem metabolic processes.
Phillips
Genevieve
G
Fluorescence Microscopy Facility, Cancer Research and Treatment Center, University of New Mexico, Albuquerque, New Mexico, United States of America.
Reith
Frank
F
Qualls
Clifford
C
Ali
Abdul-Mehdi
AM
Spilde
Mike
M
Appenzeller
Otto
O
D001106:Archaeology / Q000379:methods; D001419:Bacteria / Q000378:metabolism*; D049921:Cupriavidus / Q000254:growth & development / Q000378:metabolism; D054750:Ecotoxicology / Q000379:methods; D049429:Forensic Pathology / Q000379:methods; D006046:Gold / Q000032:analysis / Q000378:metabolism*; D006197:Hair / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D013058:Mass Spectrometry; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D011180:Postmortem Changes; D012987:Soil / Q000032:analysis*; D012988:Soil Microbiology; D013052:Spectrometry, X-Ray Emission
D012987:Soil; D006046:Gold