Human Microbiome Species and Genes for Human Identification

As submitted by the proposer:

People transfer their DNA onto objects (i.e., touch DNA). Therefore, a signature is left that can be exploited to determine the identity of an individual who may have handled an object. Forensic DNA typing characterizes genetic signatures from human biological samples. To attempt to obtain results from trace level samples, methodology modifications are made that increase the sensitivity of detection of current DNA typing methods. Collectively, the methods are known as low copy number (LCN) typing. Under LCN typing, limited template analyses suffer from exaggerated stochastic effects and with increased sensitivity there is a greater potential for contamination. This lack of reproducibility with LCN typing results has not deterred the interest in LCN typing and its potential use for developing investigative lead purposes. One way to partially overcome the limitations of LCN typing methodology is to employ an orthogonal approach. The human microbiome may provide that orthogonal approach to enable more robust results from trace level or touch biological evidence for source identification. In fact, humans carry 10 times more bacterial cells than human cells, and thus it is conceivable that more bacterial genomes are deposited than human cells on touched items. Diversity data are becoming available to define the communities that make up the human microbiome. Although the human microbiome has a wide range of functions and is quite variable, there are some common species among humans. However, little work has been carried out on what microorganisms are common to all humans, how individualizing a composite bacterial DNA profile may be, and what portion of these common human microbiome species are stable throughout an individual’s lifetime (or at least for reasonably long time periods). To answer these questions a defined set of genetic markers are needed to develop an assay to identify at species level such bacteria and then a set of bacterial species can be assayed to determine those microorganisms best suited for human identity testing. This proposal intends to assess 192 housekeeping genes for species level identification of complex bacterial communities and then select a panel of these genes to screen human subjects to determine the most abundant species that are common to all subjects. The candidate species genetic housekeeping gene sequence profiles of the selected species will be analyzed to determine the discrimination power which in
turn will provide information on the potential individualization of their human host.

This project contains a research and/or development component, as defined in applicable law.

ca/ncf