Unraveling the ancient fungal DNA from the Iceman gut

BackgroundFungal DNA is rarely reported in metagenomic studies of ancient samples. Although fungi are essential for their interactions with all kingdoms of life, limited information is available about ancient fungi. Here, we explore the possibility of the presence of ancient fungal species in the gut of & Ouml;tzi, the Iceman, a naturally mummified human found in the Tyrolean Alps (border between Italy and Austria).MethodsA robust bioinformatic pipeline has been developed to detect and authenticate fungal ancient DNA (aDNA) from muscle, stomach, small intestine, and large intestine samples.ResultsWe revealed the presence of ancient DNA associated with Pseudogymnoascus genus, with P. destructans and P. verrucosus as possible species, which were abundant in the stomach and small intestine and absent in the large intestine and muscle samples.ConclusionWe suggest that & Ouml;tzi may have consumed these fungi accidentally, likely in association with other elements of his diet, and they persisted in his gut after his death due to their adaptability to harsh and cold environments. This suggests the potential co-occurrence of ancient humans with opportunistic fungal species and proposes and validates a conservative bioinformatic approach for detecting and authenticating fungal aDNA in historical metagenomic samples.