Isolation and characterization of live yeast cells from ancient vessels as a tool in bio-archeology

Abstract

Ancient fermented food has been studied based on recipes, residue analysis and ancient-DNA techniques and reconstructed using modern domesticated yeast. Here, we present a novel approach. We hypothesize that enriched yeast populations in fermented beverages could have become the dominant species in storage vessels and the descendants of these yeast could be isolated and studied long after. To this end, using a pipeline of yeast isolation from clay vessels developed here, we screened for yeast cells in beverage-related and non-related ancient vessels and sediments, from several archeological sites. We found that yeast cells could be successfully isolated specifically from clay containers of fermented beverages. Genomic analysis revealed that these yeast are similar to those found in traditional African beverages. Phenotypically, they grow similar to modern-beer producing yeast. Both strongly suggesting that they are descendants of the original fermenting yeast. These findings provide modern microorganisms as a new tool in bio-archeology. ImportanceSo far, most of the study of ancient organisms was based mainly on the analysis of ancient DNA. Here we show that it is possible to isolate and study microorganisms, yeast in this case, from thousands of years old clay vessels, used for fermentation. We demonstrate that it is highly likely that these cells are descendants of the original yeast strains which participated in the fermentation process and were absorbed into the pottery vessels. Moreover, we characterize the isolated yeast their genome and the beer they produce. These results open new and exciting avenues in the study of domesticated microorganisms and contribute significantly to the fields of bio and experimental -archeology that aims to reconstruct ancient artifacts and products.