Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Department of Plant Pathology and Microbiology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.
Forensic Sci Int Genet. 2019 Jan;38:195-203. doi: 10.1016/j.fsigen.2018.11.010. Epub 2018 Nov 8.
The ubiquity, heterogeneity and transferability of soil makes it useful as evidence in criminal investigations, especially using new methods that survey the microbial DNA it contains. However, to be used effectively and reliably, more needs to be learned about the natural distribution patterns of microbial communities in soil. In this study we examine these patterns in detail, at local to regional scales (2 m-260 km), across an environmental gradient in three different soil types. Geographic location was found to be more important than soil type in determining the microbial community composition: communities from the same site but different soil types, although significantly different from each other, were still much more similar to each other than were communities from the same soil type but from different sites. At a local scale (25-1000 m), distance-decay relationships were observed in all soil types: the farther apart two soil communities were located, even in the same soil type, the more they differed. At regional-scale distances (1-260 km), differences between communities did not increase with increased geographic distance between them, and the dominant factor determining the community profile was the physico-chemical environment, most notably annual precipitation (R = 0.69), soil sodium (R = 0.49) and soil ammonium (R = 0.47) levels. We introduce a likelihood-ratio framework for quantitative evaluation of soil microbial DNA profile evidence in casework. In conclusion, these profiles, along with detailed knowledge of natural soil microbial biogeography, provide valuable forensic information on soil sample comparison and allow the determination of approximate source location on large (hundreds of km) spatial scales. Moreover, at small spatial scales it may enable pinpointing the source location of a sample to within at least 25 m, regardless of soil type and environmental conditions.
土壤的普遍性、异质性和可转移性使其成为刑事调查中的有用证据，特别是使用新方法调查其所含的微生物 DNA。然而，为了使其能够被有效地、可靠地使用，我们需要更多地了解土壤中微生物群落的自然分布模式。在本研究中，我们在三个不同土壤类型的环境梯度上，在局部到区域尺度（2 m-260 km）上详细研究了这些模式。研究发现，地理位置比土壤类型更能决定微生物群落的组成：来自同一地点但不同土壤类型的群落，尽管彼此之间存在显著差异，但彼此之间仍然比来自同一土壤类型但来自不同地点的群落更为相似。在局部尺度（25-1000 m）上，所有土壤类型都观察到距离衰减关系：两个土壤群落之间的距离越远，即使在同一土壤类型中，它们之间的差异也越大。在区域尺度距离（1-260 km）上，群落之间的差异不会随着它们之间地理距离的增加而增加，决定群落特征的主要因素是理化环境，特别是年降水量（R = 0.69）、土壤钠（R = 0.49）和土壤铵（R = 0.47）水平。我们引入了一种似然比框架，用于定量评估案件中土壤微生物 DNA 图谱证据。总之，这些图谱以及对土壤微生物生物地理学的详细了解，为土壤样本比较提供了有价值的法医信息，并允许在大（数百公里）空间尺度上确定大致的来源位置。此外，在小空间尺度上，无论土壤类型和环境条件如何，它都可以将样本的来源位置精确定位在至少 25 m 范围内。
