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