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Forensic Identification using Skin Bacterial
Communities
Human skin harbors large numbers of bacteria
Studies have shown skin-associated bacterial communities are diverse
So diverse that only 13% of bacterial phylotypes are shared between any given person.
Bacteria Flora
Bacteria communities are actually fairly stable as well
Communities return to normal within hours of hand washing.
Individuals have personally unique, temporary stable, and transferable skin-associated bacterial colonies.
The authors hypothesize that they could use the residual skin bacteria left on objects for forensic identification, matching the bacteria on the object to the skin-associated bacteria of the individual who touched the object.
Hypothesis
Three criteria had to be met◦ The bacteria collected had to allow for adequate
characterization◦ Skin bacteria had to persist for days to week◦ Surfaces touched had to be linked to individuals
by a degree of similarity.
Experiment Design
For the keyboard study, three individuals and their keyboards were swabbed.
For the mouse study they used nine individuals.
For the “storage” study they swabbed 2 healthy adults in the right axillary.
Methods and Materials
Target gene 16s rRNA Used MO BIO PowerSoil DNA Isolation kits. 0.1% Agarose gels were used DNA staining was done using SYBR sage
DNA gel stain in 0.5xTBE Pyrosequencing was carried out using454
Life Sciences genome Sequencer FLX instrument.
DNA Extracting and Pyrosequenceing
Pyrosequencing
This image has been created during "DensityDesign Integrated Course Final Synthesis Studio" at Polytechnic University of Milan, organized by DensityDesign Research Lab. Image is released under CC-BY-SA licence. Attribution goes to "Jacopo Pompilii, DensityDesign Research Lab"
PCR
http://www.foodsafetywatch.org/features/a-revolution-in-the-microbiology-laboratory/
Keyboard Results
http://www.pnas.org/content/107/14/6477/F1.expansion.html
Keyboard Results
http://www.pnas.org/content/107/14/6477/F2.expansion.html
Storage Results
http://www.pnas.org/content/107/14/6477/F3.expansion.html
Mouse Results
http://www.pnas.org/content/107/14/6477/F4.expansion.html
Criteria one and three met. Bacteria communities resembled that of the
owners hands. Similarity between the colonies was shown. Bacteria can be recovered from relatively
small surfaces.
Keyboard Conclusion
Two individuals bacterial communities stayed relatively similar.
Standard indoor conditions showed the bacterial community owner could still be reasonably identified
Storage Conclusion
Showed bacterial communities still remained unique to their owners
They remained unique after time had passed.
Was compared to 270 stored bacterial community genomes.
Mouse Conclusion
More studies like this are needed Forensics is a science that needs to be sure
and certain of results. Further testing would allow for more
accuracy
More Studies Needed
Fierer, Noah, et al. "Forensic identification using skin bacteria communities." Proceedings of the National Academy of Sciences of the United States of America 107.14 (2010): 6477-6481. Web.
Lawley, Rochard. A Revolution in the Microbiology Labratory. 7 October 2009. web site. 22 February 2015. <http://www.foodsafetywatch.org/features/a-revolution-in-the-microbiology-laboratory/>.
References