Development and Application of Bacterial Molecular Fingerprinting for Soil Forensics

Edouard Jurkevitch, Plant Pathology and Microbiology, The Hebrew University of Jerusalem, Rehovot, Israel

Soils are mostly defined through their chemical and physical components. These, in turn, are affected by abiotic parameters e.g. climate and topography, and by biotic factors. However, the largest of the biological dimensions, the microorganisms, is mostly ignored in soil characterization and is almost totally absent in forensics applications. This is due, among other reasons, to the ability to define soil microbial communities in detail being relatively novel, and to a lack of sensitization.

Soil microbial community analysis can reveal the effect of ecological factors, of agricultural practices, on diversity, nutrient recycling, xenobiotics breakdown, and enable the matching of samples of unknown provenance with obvious forensics implications.

The MiSAFE project, supported by the EU FP7 aimed at developing methods for soil bacterial fingerprinting applied to forensics. The programme will be presented with a focus on methodologies that were developed and their applications and limits.

We examined soil series composed of three soil types across distances ranging from meters (within soil)  to kilometers (between soils in the same region, under similar climatic conditions) to hundreds of kilometers (between soil series) all the while performing a comparative analysis of methods including marker gene choice, fingerprinting and sequencing. Terminal restriction fragment length polymorphism was the most efficient and was further developed using the 16S rRNA gene as a marker, distinguishing between soils and within soils at the tens of meter scale. Further, 18 different data analysis procedures were evaluated.

Bacterial soil communities were greatly affected by seasons, this difference between larger than soil/geographical differences. A microcosm experiment under controlled conditions was performed to assess the effect of artificial summer and winter conditions on bacterial community structure and their dynamics. The data suggested that initial composition may be decisive in determining the course of changes in bacterial communities under fluctuating conditions. 

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