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Scientific American , February 19, 2012

Raising the Dead: New Species of Life Resurrected from Ancient Andean Tomb
Ecuadorian scientists have revived a new species of yeast from pre-Incan tomb, illuminating prehistoric life

By R. Douglas Fields

QUITO, ECUADOR—Long before the Spanish conquered the Incas in 1533, and centuries before the Incas inhabited this area, the present-day site of Quito International Airport was a marshy lake surrounded by Indian settlements—the Quitus on one shore and the Ipias on the other. Between A.D. 200 and 800 these cultures prospered here, fishing the lake, growing corn, beans and potatoes in the fertile soil, and fermenting an alcoholic drink—chicha—made of a watery corn broth.

In 1980, while clearing land for new construction in a warren of graffiti-covered cinderblock shanties bristling with barbwire and defended by concrete walls tipped with broken glass, workers scraped open a tomb that had been hidden for over a millennium beneath the ramshackle neighborhood. Then, nine more deep-welled tombs were uncovered in the volcanic rock, each containing about 20 bodies. The walls of the shafts were lined with Quitus remains, each one crouched in the fetal position, clothed in the finest textile, adorned with gold jewelry, and surrounded by pottery containing offerings of food and chicha for the afterlife.

Yeast biologist Javier Carvajal Barriga, of the Pontificia Universidad Católica del Ecuador in Quito, collected scrapings from inside large, torpedo-shaped clay fermentation vessels taken from one of the tombs in an attempt to recover microbes that had fermented the ancient chicha and, if possible, revive them.

Under the sterile conditions of his laboratory, he scratched away the surface layers from inside the fermentation vessels hoping to collect yeast trapped deep in the pottery's pores. Using a special method that he devised to humidify the desiccated cells, repair their damaged membranes, and jump-start their arrested metabolisms, he coaxed a community of yeasts, which had lain dormant in the entombed vessels since A.D. 680, back to life. Carvajal says he resurrected "a consortium of yeasts" from the containers, but none of the yeasts were Saccharomyces cerevisiae—the type used in modern fermentation. They were primarily strains of the genus Candida, closely related to the well-known yeast that causes skin and vaginal infections. But careful genetic analysis showed that two strains of yeast were a new species of Candida, which he named C. theae, meaning "tea."

These findings confirm 16th-century reports of how indigenous people in the Ecuadorian Andes fermented their chicha. According to Spanish chroniclers, Inca Indians initiated fermentation using animal bones, human saliva and even human feces.

"The most closely related species to C. theae are C. orthopsilosis, C. metapsilosis and C. parapsilosis, all of which are found in human saliva and feces," Carvajal says. Indeed he found human-associated C. parapsilosis, along with C. tropicalis, among the community of yeast in the ancient fermentation vessels. C. parapsilosis is the second-most commonly isolated pathogenic species of Candida infecting people. "Also [there are] the Crytococcus saitoi and C. laurentii that are related to respiratory diseases. They [the Quitus] were chewing and spitting the corn [into the fermentation vessels], so we can assume this population probably had some respiratory problems caused by pathogenic yeasts."

© 2012 Scientific American, a Division of Nature America, Inc.

This article originally appeared here.

Photo © Paul S. Hamilton