This research determined the optimal conditions for storing soil when using biochemicals as trace evidence.
One recent development for analyzing soil as trace evidence is to use the biochemical molecules from soil microbial communities to make a fingerprint of the soil sample. The current research investigated what changes occur to the microbial community profile during the storage of a soil sample. The two phases of the research consisted of an analysis of how soil storage conditions impacted DNA profiles of soil microbial biochemical molecules of soil and also their fatty acid profiles. The first phase determined that storage treatment did not have a significant influence on the genetic profile of soil bacteria. Although the DNA genetic profiles differed among soil samples collected from four different sites, the conditions of soil storage persisted in having little effect on DNA characterization. DNA profiles were determined through capillary electrophoresis-single stranded conformation polymorphism (CE-SSCP). Statistical analysis used Bray-Curtis distances and analysis of similarity (ANOSIM). In the second phase of the research, the fatty acid profiles of soil microbial biochemical molecules were analyzed as fatty acid methyl esters (FAMEs) using gas chromatography-mass spectrometry. Data were analyzed using canonical correlation analysis, squared Mahalanobis distance, and repeated measures. The FAME data indicated that in order to preserve the integrity of the microbial community fatty acid profile, the best storage temperature is -80 degrees centigrade, although storage at -20 degrees centigrade proved to be an acceptable alternative. Thus, the researchers conclude that the analysis of fatty acid profiles is more sensitive to changes in the microbial habitat than that of DNA profiles. The researchers recommend the creation of a soil microbial community profile database. Soils that have been archived could be used, and new collections would be required. 7 tables, 5 figures, approximately 70 references, and appended supplementary data