Metagenomics, Lyme Disease, and the Tyrolean Iceman’s Tattoos

When the genetic analysis of the 5,300 year old Tyrolean Iceman, better known as Ötzi, was published in February, most of the attention was naturally focused on his genomic DNA. His genomic DNA produced some interesting results: he had brown eyes, blood type O+, was probably lactose intolerant and from a southern European gene pool. He also had a collection of alleles that associate with atherosclerosis that correlate with calcifications found by CT scan in Ötzi’s arteries.

To round out a complete analysis of the single 100 mg specimen they took from Ötzi’s ileum, the largest bone of the pelvis, they did a metagenomic analysis to identify all of the non-human DNA sequences amplified. Pelvis is not really an ideal bone to take a specimen from given its proximity to the intestinal organisms that play a role in decomposing the body. Surprisingly, bacterial DNA was a very small 0.84% of the identified sequences. They oddly make no reference to the 18% of DNA reads identified as “other eukaryote”.  Of the bacterial species, 72% of the sequences were from the genus Clostridia, who are primarily spore-forming anaerobes found in the soil. The one pathogen of significance discovered was Borrelia burgdorferi, the agent of Lyme disease.

Iceman metagenome (Keller et al, 2012)

Dark field image of Borrelia burgdorferi. Photo Credit: CDC

The break down of the Iceman’s microbial phylum yielded an impressive array of bacterial diversity.  The Firmicutes include the anaerobic Clorstridium species that are found in the soil. The Proteobacteria include the enteric bacteria like Escherichia coli, many of which are facultative anaerobes. Both of these phylum would be included in decomposition of the body and as anaerobes could grow in the corpse. Borrelia burgdorferi, the agent of Lyme disease, belongs to the phylum Spirochaetes. They were able to sequence approximately 60% of the Borrelia burgdorferi genome. To find B. burgdorferi in the pelvis suggests that the infection was in a systemic phase.

There are two pieces of correlating data to support a Borrelia burgdorferi infection. The international team that did this work linked the infection with Ötzi’s atherosclerosis, an association previously shown between Lyme disease and several other systemic infections.

Tattoos on the Iceman cover or align with major joints and muscles. (South Tyrol Museum of Archaeology site)

Yet, a common symptom of systemic Lyme disease is joint and muscle pain. One of the earliest observations of Ötzi’s mummy is that he has a lot of tattoos specifically placed over joints and muscle groups in places where strain would be expected. These tattoos do not appear to be decorative or signs of inclusion in a community. Consensus appears to have formed early on that these tattoos were medicinal, probably for pain relief. Scans of the mummy do suggest some arthritis. With his lifestyle, an approximately 45-year-old man is expected to have some arthritis and pain.  Both atherosclerosis, and evidence of joint pain and some arthritis can be explained by other means, but when taken together with the B. burgdorferi DNA make a compelling case that Lyme disease contributed to his overall state of health.

Reference:

Keller, A., Graefen, A., Ball, M., Matzas, M., Boisguerin, V., Maixner, F., Leidinger, P., Backes, C., Khairat, R., Forster, M., Stade, B., Franke, A., Mayer, J., Spangler, J., McLaughlin, S., Shah, M., Lee, C., Harkins, T., Sartori, A., Moreno-Estrada, A., Henn, B., Sikora, M., Semino, O., Chiaroni, J., Rootsi, S., Myres, N., Cabrera, V., Underhill, P., Bustamante, C., Vigl, E., Samadelli, M., Cipollini, G., Haas, J., Katus, H., O’Connor, B., Carlson, M., Meder, B., Blin, N., Meese, E., Pusch, C., & Zink, A. (2012). New insights into the Tyrolean Iceman’s origin and phenotype as inferred by whole-genome sequencing Nature Communications, 3 DOI: 10.1038/ncomms1701

South Tyrol Museum of Archaeology permanently houses and studies the mummy.