Graphic image of Lactobacillus bacteria.

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Stanford Medicine Scope - December 1st, 2016 - by Rosanne Spector

Prions are notoriously dastardly — after all, these infectious proteins are the cause of mad cow disease and Creutzfeldt-Jakob disease. But researchers have been turning up evidence that some prions have a heroic side under certain circumstances. And now, in a series of experiments described this week in eLife, a team of Stanford and Harvard researchers has identified a chemical that gives yeast cells a prion-based superpower of sorts.

The yeast species they studied, Saccharomyces cerevisiae (the same type of yeast used in brewing and baking), normally loves supping on glucose. But it’s also true that yeast cells living in places where glucose is scarce manage to subsist on other food sources. Just a few years ago, a team of researchers got a clue as to how: They discovered that prions activated by a compound released by bacteria enable the yeast to dine on a wider range of sugars, bypassing their ancient metabolic craving for plain glucose. But what is this mystery compound?

One of those researchers, Daniel Jarosz, PhD, now an assistant professor of chemical and systems biology at Stanford, organized a team to find out: Stanford postdoctoral fellow David Garcia, PhD; Harvard postdoctoral fellow David Dietrich, PhD; and Harvard professor Jon Clardy, PhD. In the recent eLife paper, they reveal the compound: lactic acid, a simple chemical produced by many bacteria — it’s the same compound released by Lactobacillus species that makes yogurt taste sour, and it even influences the metabolism of some cancers.

“This suggests that many other simple molecules in nature secreted by bacteria could also be co-opted to fuel unexpected transformations in cell behavior,” said Garcia. One of the Jarosz lab’s next steps will be to try to identify other chemical messages used by microbes to induce other prions in yeast or other organisms.

And here’s an interesting thought: The human body teams with trillions of bacterial cells, and often yeast cells as well. Might these bacteria within the human microbiome be communicating with prions to affect our health in lasting ways?

A perspective based on this article that appears in the same journal issue highlights how bacteria-prion communication could explain some of the quirks of winemaking. In fact, this work provides a molecular explanation for why lactic acid-producing bacteria are often associated with failed wine fermentations — a phenomenon Louis Pasteur pondered over 140 years ago.

Originally published at Stanford Medicine Scope Blog