How Yeast in Kombucha Tea ‘Selfishly’ Rigs The Genetic Game

Aug 24, 2017

In the cooler section of any Whole Foods store or maybe the cup holder of your crunchy neighbor’s VW bus, you can find Kombucha, the yeast-fermented tea sold with some pretty over-the-top marketing claims.

“The mission of Unity Vibration kombucha is to spread love, health and possibility in to the world and to better the lives of millions with our products,” touts one online kombucha commercial.

But for all of kombucha’s peace and love image, research at the Stowers Institute in Kansas City shows some rather sinister activity when the yeast cell that’s found in it mates.

Stowers assistant investigator Sarah Zanders started working with Schizosaccharomyces kambucha yeast, to use its scientific name, while conducting research in Seattle, although she’s never been a fan of the tea itself.

“I’m very thankful for the tea, because it’s given me a career, but I don’t myself drink it,” Zanders says.

Zanders focuses on exploring the workings of “selfish” genes, a concept popularized by evolutionary biology Richard Dawkins in his 1976 book “The Selfish Gene.” In it, Dawkins argues that genes competing for survival not only drive biological evolution but also animal and human behavior.

Mostly an abstract argument then, now, thanks to researchers like Zanders, scientists have discovered not only that specific selfish genes exist but how they function.

Normally during mating – whether it’s yeast, mice or humans – there’s a kind of showdown to decide which genes get passed along to the next generation and which don’t.

The WTF4 gene, found in S. kambucha, produces both a poison, shown in pink, and an antidote, shown in blue, that are passed along to its offspring.
Credit Stowers Institute for Medical Research

Malicious maneuver  

But some varieties of S. kambucha contain a selfish gene called WTF4, which hijacks the reproduction process using a particularly malicious maneuver: They pass along to their offspring a poison designed to kill them.

“What we’ve likened in to is like an Agatha Christie-type murder scenario,” Zanders says.

Or better yet, perhaps, the 1987 cult classic “The Princess Bride.”

When a cell with the WTF4 gene mates with a cell that doesn’t have it, the resulting genetic battle is not unlike the scene in the movie where Westley, the ninja-like hero played by Cary Elwes, faces off against Vizzini, the wannabe criminal mastermind played by Wallace Shawn.

Westley takes two cups of wine and tells Vizzini he’s secretly dosed one with a poison called “iocane powder.” 

He sets both cups on a table and lets Vizzini choose who will drink from which one. After a few minutes of verbal gymnastics and a sly switcheroo, Vizzini grabs a cup, gulps it down and – spoiler alert – drops dead.

Princess Buttercup, whom Wesley has come to rescue and is played by Robin Wright, then says: “To think, all that time it was your cup that was poisoned.”

Wesley explains his secret.

“They were both poisoned,” Westley says. “I spent the last few years building up an immunity to iocane powder.”

The WTF4 gene has a similar trick up its sleeve.

Poison and antidote

When it reproduces, it poisons all of its offspring, but to the offspring lucky enough to inherit the WTF4 gene, it also passes along the ability to create an antidote to save itself. By doing this, the gene basically rigs the game to preserve its continued existence generation after generation.

University of Maryland biology professor Gerald Wilkinson says Zanders’ research offers a rare window into what’s happening inside selfish genes. 

“There are many examples, but the genetic details of those systems are not that well understood in most cases,” Wilkinson says.

Selfish genes are found throughout nature and have a lot of different ways to rig the genetic game. There are even some that use a poison-and-antidote technique similar to the WTF4. But typically, they work in teams, with one gene creating the poison while another creates the antidote.

Wilkinson says that Zanders’ research is remarkable because it shows a single gene doing both.

“In this case, they found a gene that has both the poison and the antidote,” Wilkinson says. “That is unique. I don’t think that’s been seen in any other system that I’m aware of.”

Selfish genes like the WTF4 might seem like a good thing for an organism hoping to pass along its DNA, but their selfishness doesn’t necessarily pay off for the organism in the long run.

That’s because while selfish genes hijack the genetic lottery in their favor, they also muck with natural selection.

“Genes are stuck together, and they are kind of inherited in groups,” Zanders says. “And what can happen is that if junk accumulates next to a selfish gene, it is transmitted along with the selfish gene.”

Researchers think this “junk” might include genetic predispositions to certain diseases that would normally get weeded out over the generations. Instead, they get passed along thanks to the shield of protection provided by neighboring selfish genes.

Some scientists are now working to borrow selfish techniques and use them in engineered DNA, hoping they can steer evolution to reduce populations of, say, mosquitoes carrying Zika or other pests that we’d like to get rid of.  

Zanders says the first step is understanding how to cheat the evolutionary process.

“Like human society, there’s a million different ways to cheat to get ahead, and we’re just starting to appreciate some of the strategies that selfish genes are employing to do that,” Zanders says.

And by learning how to be genetically selfish, researchers may perversely give humans a competitive edge to help them stay healthy. 

Alex Smith is a health reporter for KCUR. You can reach him on Twitter @AlexSmithKCUR.