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The use of soil as trace evidence has changed significantly with the addition of new techniques. These techniques include using the biochemical molecules from soil microbial communities to make a fingerprint of the specific soil. This research examines the changes to the microbial community profile that take place during storage of a soil sample. To observe such changes both the DNA and fatty acid profiles will be examined.
The DNA profiles were made with capillary electrophoresis-single stranded conformation polymorphism (CE-SSCP). After statistical analysis using Bray-Curtis distances and ANOSIM (analysis of similarity) it was shown that storage of soil does not have a significant impact on the microbial community profile. However, when samples were compared across soil collection sites significant differences were seen. This illustrates that different soils respond differently to storage treatments.
The fatty acid profiles were analyzed as fatty acid methyl esters (FAMEs) using gas chromatography. Data were analyzed using canonical correlation analysis, squared Mahalanobis distance, and repeated measures. The results show that -80˚C is the best way to store soils to preserve the integrity of the microbial community FAME profile, followed by -20˚C. It was also demonstrated that when using fatty acids to examine the change within the soil at the collection site there is generally not a significant difference between the soil collected over a two week period.
When the two methods are compared FAME is a more sensitive method to minute changes within the microbial community. With the data from these two methods, using soil microbial community profiling is closer to becoming a viable option for forensic science.
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