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There are tons of cooperative  relationships in nature. And one  of the most obvious is between bees and flowers.

Bees visit flowers for their  tasty pollen and nectar,   and they help pollinate the plant as they go! We've known about this for years,   and it's so basic that you probably  learned about it in elementary school. But hold on to your juice boxes and kickballs,  because this story is more interesting than we thought.   In fact, there's a third, much  tinier member of this relationship: yeast.

Yeast is a fungus found all over  the globe. And the types that live in your garden do a bunch of important jobs. For instance, they help plant matter  decompose, and they help roots absorb nutrients and water.

Some of them also hang  out in nectar, where they feed on its sugar. So, there's obviously some plant/yeast  friendliness going on here.   But as for how pollinators factor  into that… that took a bit to sort out. Like, because yeast eats the nectar's sugar,   pollinators might get less nutrition from  yeasty nectar.

So maybe they'd avoid it. Then again, a 2018 study showed that yeast can  change a nectar's scent by altering its chemistry   — and we know scent affects pollinators,  too. So maybe that factors into this somehow?

Really, there are a lot of variables. So in  2019, a group in Belgium   set out to get a better understanding of the role yeast actually plays in the pollinator-plant relationship. In one experiment, they took buff-tailed  bumblebees and introduced them to a field of fake flowers.

Some contained a yeast and  sugar solution, and others just had sugar water. They had hypothesized that  the yeast would negatively impact the bees' behavior and health, except…. Well, not only did the bees show  no aversion to the yeasty flowers;   the yeast helped their colonies grow.

The hives that ate this nectar   even had fewer larvae die, which led to more  worker bees and an overall healthier colony. We'll need more research to say why,   but the authors think this could be because  yeast stores nutrients in its cell walls.   So even if the nectar has fewer nutrients,  the yeast might ultimately help the bees. Through other tests, the team even   discovered that yeasts could suppress  the growth of a bumblebee gut parasite   called Crithidia bombi, which might play a  role in the overall decline of honey bees.

Again, the team isn't totally sure why, but  they suspect the yeast could be out-competing   the parasite for food in the bee's gut. Which  is pretty metal for a single-celled organism. So, based on this, it looks like nectar  full of yeast is helpful for bumblebees.

And the bees help the yeast, too:  As they move from flower to flower,   they take the fungi with  them and spread them around! And just to really come full circle  here, that's even good for the flowers. A study published in 2010 found that yeast  gives off heat as it breaks down sugar.   So yeast in nectar increased flowers'  temperatures by up to six degrees Celsius.

Then, another study published in 2013 found  that bumblebees are more likely to feed from warmer flowers,   probably because it makes  the nectar less sticky and easier to drink. So, the yeast might be making flowers  more appealing to bumblebees, too.   And since bumblebees are pollinators... well,  it's a happy love triangle for everyone. If you love asking questions about the world,   you might also have fun with  Brilliant's Daily Challenges.

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