Citizen Science #32 by Roberta McLain

Order in a Constantly Changing Microbial World

The first warm afternoon of spring sends many of us outside. A few minutes stacking wood, clearing branches, planting seedlings, or any of the other things we do outside in March or April and it’s easy to come home with dirt under our fingernails.

What’s hard to see is that the soil is alive with billions of microscopic organisms, such as bacteria and fungi. These microbes are not intruders or invaders; they are essential to the health of the soil and plants.

Something similar is happening inside us.

Most of us think of our bodies as a single organism—just us. But the story is more complicated.

Trillions of bacteria, fungi, and other microbes live on our skin, in our mouths, and in our gut. Together, they form what scientists call the human microbiome.

They arrive during and immediately after our birth and they shift from day to day, month to month and year to year. A meal, a walk in the woods, a course of antibiotics and even the changing seasons can change which microbes are present.

At first glance, this microscopic world may look chaotic: trillions of microbes growing, competing and constantly replacing one another. But in science, chaos does not mean disorder. It describes systems that are always shifting and competing but are shaped by underlying rules.

Systems like this, where millions of small interactions produce surprising order, are one of the puzzles this column hopes to explore this year.