Meiklejohn Kelly A, Jackson Megan L, Stern Libby A, Robertson James M
Counterterrorism and Forensic Science Research Unit, Visiting Scientist Program, Federal Bureau of Investigation Laboratory Division, 2501 Investigation Parkway, Quantico, VA, 22135, USA.
Department of Forensic Science, Virginia Commonwealth University, 1015 Floyd Avenue, Richmond, VA, 23284, USA.
Int J Legal Med. 2018 Nov;132(6):1515-1526. doi: 10.1007/s00414-018-1772-1. Epub 2018 Feb 8.
Soil is often collected from a suspect's tire, vehicle, or shoes during a criminal investigation and subsequently submitted to a forensic laboratory for analysis. Plant and insect material recovered in such samples is rarely analyzed, as morphological identification is difficult. In this study, DNA barcoding was used for taxonomic identifications by targeting the gene regions known to permit discrimination in plants [maturase K (matK) and ribulose 1,5-biphosphate carboxylase (rbcL)] and insects [cytochrome oxidase subunit I (COI)]. A DNA barcode protocol suitable for processing forensic-type biological fragments was developed and its utility broadly tested with forensic-type fragments (e.g., seeds, leaves, bark, head, legs; n, 213) isolated from soils collected within Virginia, USA (n, 11). Difficulties with PCR inhibitors in plant extracts and obtaining clean Sanger sequence data from insect amplicons were encountered during protocol development; however, the final protocol produced sequences specific to the expected locus and taxa. The overall quantity and quality of DNA extracted from the 213 forensic-type biological fragments was low (< 15 ng/μL). For plant fragments, only the rbcL sequence data was deemed reliable; thus, taxonomic identifications were limited to the family level. The majority of insect sequences matched COI in both GenBank and Barcode of Life DataSystems; however, they were identified as an undescribed environmental contaminant. Although limited taxonomic information was gleaned from the forensic-type fragments processed in this study, the new protocol shows promise for obtaining reliable and specific identifications through DNA barcoding, which could ultimately enhance the information gleaned from soil examinations.
在刑事调查过程中，通常会从嫌疑人的轮胎、车辆或鞋子上采集土壤，随后将其送交法医实验室进行分析。在此类样本中发现的植物和昆虫材料很少被分析，因为形态学鉴定很困难。在本研究中，通过靶向已知可用于区分植物的基因区域[成熟酶K（matK）和核酮糖-1,5-二磷酸羧化酶（rbcL）]以及昆虫的基因区域[细胞色素氧化酶亚基I（COI）]，使用DNA条形码进行分类鉴定。开发了一种适用于处理法医类型生物片段的DNA条形码方案，并在美国弗吉尼亚州采集的土壤（n = 11）中分离出的法医类型片段（例如种子、叶子、树皮、头部、腿部；n = 213）上广泛测试了其效用。在方案开发过程中遇到了植物提取物中PCR抑制剂的问题以及从昆虫扩增子获得干净的桑格测序数据的困难；然而，最终方案产生了特定于预期位点和分类群的序列。从213个法医类型生物片段中提取的DNA的总体数量和质量较低（<15 ng/μL）。对于植物片段，只有rbcL序列数据被认为是可靠的；因此，分类鉴定仅限于科级水平。大多数昆虫序列在GenBank和生命条形码数据系统中均与COI匹配；然而，它们被鉴定为一种未描述的环境污染物。尽管从本研究中处理的法医类型片段中收集到的分类信息有限，但新方案显示出通过DNA条形码获得可靠和特定鉴定的前景，这最终可能会增加从土壤检查中收集到的信息。
