There is a miracle in my refrigerator.

I'm not referring to the leftovers from the delicious lamb curry that my wife, Linda, prepared last night for supper. I'm referring to something even more spectacular.

Can you guess what it is?

Here's a clue — bakers and pastry-makers routinely experience this miracle. Give up?

It's a packet of dry yeast.

Before you say, "No way, Steve," consider the marvel in this package. Inside is a tan-colored, granular substance, which is comprised of yeast cells that have been dried and coated with an inert material.

The cells show no signs of life. No metabolism. No reproduction. No growth. For all practical purposes, the yeast is dead.

But the cells aren't really dead. They are waiting in a state of suspended animation for a little water to rouse them from their sleep, much like the prince's kiss did for Sleeping Beauty.

Add warm water and in about the time it takes to hard-boil an Easter egg, the yeast cells will be growing, metabolizing and dividing — oblivious to their deep slumber.

In short, the yeast cells have undergone the wonder of resurrection.

The yeast cells were originally grown in large vats and then dried under controlled conditions. The cells went from an active living state to a dry nonliving condition, and finally in our kitchens they are revived with water.

Biologists call this phenomenon in which an organism can be dried and then rehydrated anhydrobiosis.

Anhydrobiosis is an adaption that evolved in organisms that live in environments where moisture availability is sporadic. A variety of microscopic animals, such as rotifers, nematodes and tardigrades, as well as fungi such as yeast, and even a few plants such as rusty woodsia (Woodsia ilvensis) are capable of resurrection.

If you've hiked around Quarry Park & Nature Preserve in Waite Park, you may have seen rusty woodsia. This fern grows in the cracks and crevices on the rocky outcrops.

When there is adequate rain, rusty woodsia looks like an ordinary fern with expanded green fronds. However, during dry periods, the fronds curl up and turn brown and the plant looks dead. A subsequent rain will kiss it back to life.

Yeast and rusty woodsia are able to resurrect because they evolved a clever mechanism to protect their cells as they dry. Unlike humans and most other organisms, the cells of anhydrobiotic organisms produce a special sugar called trehalose that acts a little like a referee to prevent irreversible chemical reactions between the dried cell components. Without trehalose, a cell can't be revived when it is rehydrated.

The practical implications of anhydrobiosis are enormous. For example, if we can figure out how to load trehalose into blood cells, the blood could be dried down and would have a long shelf life without the need for continuous donations.

All of this talk about yeast, bread and lamb curry is making me hungry. I think I'll go check out what new miracle Linda has waiting for me in the refrigerator.


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