Electronic Theses and Dissertations
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About: Electronic theses and dissertations (ETDs) are the graduate research outputs of Texas Tech University. They represent years of work from our Master's and Doctoral graduates. If you find the ThinkTech digital repository useful, please tell us! Share how open access to scholarship benefits you. Your story matters to us.
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Browsing Electronic Theses and Dissertations by Subject "16S rRNA Amplicon Sequencing"
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Item Establishing an agricultural origin of soils from footwear using a soil microbial approach(2021-08) Canales, Arrin; Mayer, Greg; Tiedemann, Paola; Phillips, Caleb; Halamek, JanForensic science describes the boundary between science and the law. Scientific evidence is often used to convict individuals of a crime or free the wrongly convicted. Forensic analysis consists of several disciplines including forensic chemistry and biology, forensic toxicology, fingerprint examination and many others. Furthermore, forensic science helps to reconstruct events through analysis of physical evidence, or evidence consisting of tangible objects. Just as the ability to associate a subject to an item of evidence can be achieved through forensic analysis of human DNA, forensic analysis of soil (or other environmental sample) DNA can be used to estimate the origin of an unknown sample or provide an association medium between crime scene samples and suspects. In an attempt to improve investigative techniques that help place an individual at a crime scene, this thesis focuses on soil microbial communities and their potential role in forensic science. In this study, source tracking algorithms that help identify the source of a “sink” (which in our case was soil collected from a shoe) were used to see whether we could link a piece of evidence to the crime scene. Given that microbes retain unique microbial signatures, these features could aid in discriminating between varying environments which a suspect has come in contact. Thus, microbial source tracking may serve as a good candidate for corroborating evidence. In addition, this study can add to existing methods used for forensic identification by strengthening the use of microbes as evidence using next generation sequencing technology. Furthermore, this microbial approach adds to the arsenal of current methods that aid forensic scientists in solving criminal investigations and can provide a better understanding of soil-derived evidence as an associative tool between an individual and a crime scene depending upon the microbial milieu that is present during evidence collection.Item Temperature effect on skin microbes used as trace evidence on knife handles(2020-08) Castro, Yaireth; Brown, Amanda M. V.; Prada-Tiedemann, Paola A.; Mayer, GregDNA analysis can be performed on a range of samples encountered at crime scenes such as blood, semen, saliva, and skin cells to identify a perpetrator. Unfortunately, such evidence may be absent or present in low quantity or quality. This dilemma has led researchers to consider alternative methods for forensic identification. A relatively new research area in forensic science has explored the use of skin bacteria as a form of trace evidence. Studies have shown that the composition of the human skin microbiome can be unique to an individual and this microbial signature can remain stable for long periods of time. Thus, DNA analysis can be performed on traces of skin microbes that are shed, much like skin cells, on some surface involved in a crime. This technique is novel and further research must be conducted to study crime scene factors that could affect the viability of analyzing microbial evidence. One important factor to consider is environmental temperature. Few forensic studies have focused on how temperature affects skin microbial signatures and consequently, the ability to use such evidence as an identification method. The studies that have explored the temperature factor have focused on storage conditions and have not conducted the experiments in a forensic context (i.e. obtaining skin microbial traces from an object exposed to varying temperatures). The current experiment involved having male and female subjects touch knife handles which were incubated at a range of temperatures for 2 weeks. Skin microbe traces were obtained from the knife handles using swabs from which microbial DNA was extracted, amplified, and sequenced to identify bacterial composition of the samples. 16S rRNA amplicon sequencing data was analyzed using QIIME 2 to identify significant changes in microbial community diversity between the reference samples and the samples obtained after a 2-week exposure to different temperatures.