Bacterial profiling of soil using genus-specific markers and multidimensional scaling

Abstract

Forensic identification of soil based on microbial DNA fingerprinting has met with mixed success, with research efforts rarely considering temporal variability or local heterogeneity in soil's microbial makeup. In the research presented, the nitrogen fixing bacteria rhizobia were specifically examined. Soils were collected monthly from five habitats for 1 year, and quarterly in each cardinal direction from the main collection site. When all habitats were compared simultaneously using Terminal Restriction Fragment Length Polymorphism analysis of the rhizobial recA gene and multidimensional scaling, only two were differentiated over a year's time, however pairwise comparisons allowed four of five soils to be effectively differentiated. Adding in 10-foot distant soils as "questioned" samples correctly grouped them in 40-70% of cases, depending on restriction enzyme used. The results indicate that the technique has potential for forensic soil identification, although extensive anthropogenic manipulation of a soil makes such identification much more tentative.