Exploration Of Application Of Palm Skin Microbiome To Human Identification

Analysis of microbiome on human palm skin hasn’t been applied to forensic science nowadays. Microbiome on human palm skin are more abundant in quantity, much easier to transfer and more stable in environment. Application of this technology can not only prove correctness of identification conclusion acquired by other technologies, but also substitute for other technologies under special conditions. The research purpose of this dissertation is to establish systematical experimental methods as well as data-processing methods to analyze microbiome on human palm skin, then design new universal primers to explore feasibility of applying this technology for forensic identification from the angles of diversity and stability.Optimized experimental methods were selected based on experimental design and data analysis. Different kinds of mock bacterial communities were established(genome sequences and copy quantities of all bacteria were known), and various kinds of experimental factors during the process of sample collection, DNA extraction, PCR amplification, and sequencing were analyzed by multivariate ANOVA. Sequencing results showed that these optimized experimental methods can not only improve efficiency of DNA extraction, but also decrease bias of PCR amplification. So sequencing results can truly represent bacterial community structure characteristic of samples.Six single-copy functional genes were selected after analysis of genome sequences of bacteria genus dominate on human palm skin. They are dna K gene(chaperone Hsp70),pyr H gene(uridylate kinase), rpo A gene(RNA polymerase subunit alpha), rps H gene(30S ribosomal protein S8), rps L gene(30S ribosomal protein S12) and tsf gene(Elongation factor Ts).Universal primers were designed based on conservative regions of these genes, then they were tested though simulated PCR. Three pairs of universal primers were anesthetized, PCR amplification conditions were optimized and samples collected from human palm skin were analyzed.During two-month period, microbiome on palm skin from both of male and female volunteers showed stable characteristics. The left palm and right palm of male volunteer shared more OTUs than the female volunteer. As time went on, there are more OTUs existed stably on palm skin of the male volunteer. The most similar microbime communities are usually the same person’s left palm and right palm, or the same person’s samples collected within short time period.Microbiome on palm prints were stable after they were left, but community structures can be affected by indoor environment microbiome. Even after several weeks, microbiome on palm prints are still quite similar to the palm prints collected weeks ago. Microbiome structures on keyboards of personal computer are more stable than palm prints. Bacteria from Trabulsiella in the air can affect community structures of palm print.Sequencing results of dna K gene, rps L gene and rps H gene showed that bacteria in samples can be identified at species level. They are very promising to differentiate samples.Sequencing results of different genes revealed different species because of primer sequences amplification efficiency various in genus. There are special OUTs in different age groups and gender groups.The results of this dissertation may be applied in forensic science and technology from several aspects. Age period, gender, and illness of suspects can be deduced though species and percentage of special OTUs. Many OTUs are stable on person’s palms, and they can be transferred through touching. After sequencing data analysis, palm prints can be matched with palms. Microbiome in the air may affect community structures of palm prints, so microbiome in vicinity area where nobody would touch should be collected as contrast while deduce time period of palm prints.