Analysis of bacterial DNA in skin and muscle of the Tyrolean iceman offers new insight into the mummification process

Abstract

About 80 sequences (16s ribosomal RNA gene) of bacterial DNA in samples of skin and muscle taken directly from the Tyrolean iceman (3350-3100 years B.C.) or recovered during the 1992 archaeological expedition at the Alpine site were analyzed to obtain clues to the natural mummification process that allowed the corpse of the Neolithic shepherd/hunter to be preserved for more than 5,000 years. The investigation was made more complex by the fact that the surface of the mummy had been swabbed with phenol soon after the discovery (September 19, 1991). Our results show that no trace of microbial DNA is left on the actual surface of the body, while the untreated skin still bears the remains of large numbers of bacteria belonging to the genera Sphingomonas, Afipia, Curtobacterium, Microbacterium, Agromyces, and others. Compared to the untreated skin, the iceman's muscle is also very rich in bacterial DNA. However, this DNA comes, with few exceptions, from the species Clostridium algidicarnis. The sharp difference in the bacterial DNA composition of skin and muscle suggests that the remains of the original cadaveric microflora of the latter have not disappeared during the iceman's taphonomic history. On the other hand, the massive presence of C. algidicarnis, a cold-adapted sporigenous, the DNA of which was previously (Ubaldi et al. [1998] Am. J. Phys. Anthropol. 107:285-295) found in the soft tissue of a naturally desiccated Andean mummy, indicates that the hypothesis that the iceman's corpse underwent rapid dehydration by the effect of a warm wind (föhn) is no longer plausible. The results best fit with the hypothesis (Bereuter et al. [1997] Chem. Eur. J. 7:1032-1038) that the body was first covered by snow and ice, and then underwent thawing and, finally, desiccation.

Abrupt tropical climate change: Past and present

“…Ö tzi was exposed in 1991 by the retreating glaciers, and his remains were radiocarbon-dated between 5.05 and 5.35 ka (39). The excellent preservation of his remains strongly suggests that he was buried quickly by snow and captured within the advancing glacier (39,40).…”

Ötzi's last meals: DNA analysis of the intestinal content of the Neolithic glacier mummy from the Alps

“…Identification of fungi by use of the 18S rDNA sequence is less accurate than that of plants. However, the fact that both the Urediniomycetes and the Heterobasidiomycetes classes include psicrophilic genera such as Leucosporidium and Mrakia and that, in addition, the consensus sequence F is very close to a fungal sequence (T44NS-7) previously obtained in a study on the DNA of the man's grass clothing (20), suggest that the fungi present in the intestines are most probably representatives of the cold-adapted microflora that developed after the corpse and the equipment became entrapped in the ice (22).…”

Sequence analysis of bacterial DNA in the colon and stomach of the Tyrolean Iceman

“…Because the extraction from low-level DNA samples is particularly sensitive to potentially contaminating DNA during the PCR process, it has been supposed that these rDNA sequences may be intrinsic contaminants of PCR reactions (Tanner et al, 1998 ). On the other hand, some of the 16s rDNA amplicons from the grass are indicative of a microbial flora (psycrophilic ␣-proteobacterium, Pseudomonas, and Arthrobacter), consistent with the environmental characteristics of the Alpine site and with the microflora composition of the Iceman's skin (Rollo et al, 2000).…”