Fluorescence Microscopy Facility, Cancer Research and Treatment Center, University of New Mexico, Albuquerque, New Mexico, United States of America.
PLoS One. 2010 Feb 19;5(2):e9335. doi: 10.1371/journal.pone.0009335.
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.
METHODOLOGY/PRINCIPAL FINDINGS: 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.
CONCLUSION/SIGNIFICANCE: 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.
痕量金属分析在头发中被用于考古学、法医学和毒理学研究，作为代谢过程的替代物。我们发现亲金属细菌介导金（Au）的沉积，金被用作死后埋葬的头发中微生物活性的示踪剂，这会影响此类分析的结果。
方法/主要发现：人类头发在含 Au 的土壤中孵育长达六个月，在天然土壤柱（实验 1）、添加了可移动 Au(III)-配合物的土壤（实验 2）和 Au 沉淀细菌 Cupriavidus metallidurans（实验 3）中，在含有 Au(III)-配合物的 Cupriavidus metallidurans 培养液中的蛋白胨-肉提取物（PME）培养基中（实验 4），以及在非含 Au 土壤中（实验 5）。使用扫描电子显微镜、共聚焦显微镜和电感耦合等离子体质谱法分析头发样本。在实验 1-4 中，Au 含量随时间增加（P = 0.038）。在实验 4 中观察到的增加最大，与实验 1 相比（平均值= 1188 与 161 μg kg(-1)，Fisher 最小显著差异 0.001）。作为头发代谢替代物的硫含量保持不变。值得注意的是，Au 与 S 的比值随时间增加（线性趋势 P = 0.02）并随添加的 Au 和细菌增加（线性趋势，P = 0.005），表明更多的 Au 沉淀细菌种群和增加的 Au 可用性增加了 Au 在头发上的沉积。
结论/意义：死后头发与土壤生物群的相互作用可能会扭曲头发分析的结果，这意味着在解释考古学、法医学和毒理学头发分析结果时，必须考虑金属含量、微生物活性和埋藏时间，这些结果迄今为止一直是生前代谢过程的替代物。
