The acne causing agent P. acnes transferred from human to grapevine in the Neolithic

Studies which have investigated the dynamics of Bacteria/Host associations have revealed numerous cases of host switches from domestic animals to humans. Much less is known about the exchange of symbionts between humans and plants, and even less about the timing of such events. Here we report the surprising and, to our knowledge, first example of an horizontal interkingdom transfer of the human opportunistic pathogen, and agent of acnes (Propionibacterium acnes) to the domesticated grapevine Vitis vinifera L. Fluorescent in-situ hybridization, phylogenetic and population genetic analyses suggest that this bacteria has a human origin and has adapted to the new host to the point of obligate, possibly endocellular, endophytism. Molecular dating indicates that this host transfer is compatible with a Neolithic domestication of grapevine by humans; we speculate that P. acnes has exploited common agronomic practices, such as grafting and pruning, to transfer to the new host.