When you hear the word “bacteria,” you might think of germs or disease. But not all bacteria are harmful. Trillions of these microorganisms — also called microbes — live on our skin and inside our bodies, but they’re too tiny to see with the naked eye.

Our microbes have important jobs, ranging from helping us digest food to protecting us from infections. The genetic material for the microorganisms — including bacteria, fungi and other microbes — that reside on or in our bodies is called the human microbiome.

Babies get microbes from parents

Where do our microbiomes come from? As babies, we get a big dose of microbes from our parents, and over time we pick up microbes from our environment. While our microbiomes are unique, they are most similar to those of the people living with us. That’s because we’re constantly sharing germs — and although this might sound gross, it’s just part of being a person.

“We’re meant to be inoculating each other all the time as humans,” said Karen Guillemin, a University of Oregon biologist who studies microbes.

The novel coronavirus, which causes covid-19, is an example of how easily we share microbes with one another.

“One thing the pandemic has really illustrated is that microbial communities aren’t limited to a single individual,” Guillemin said. “They’re fluid and transmitted between people.”

What about the hand sanitizer, disinfectant and cleaning products that we’re using to prevent the spread of the coronavirus? While these practices do have an impact on what kinds of microbes we encounter, “being sterile isn’t a feasible state for humans,” Guillemin said. “So it’s not as if we’re going to wipe out every microbe from all this sanitizing.”

But scientists are concerned about how our microbiomes are changing as a result of our modern lifestyles. With industrial and technological advances, we’re spending less time outdoors than we did decades ago — and that means less exposure to friendly microorganisms.

In a study of a population in Ecuador, Guillemin found that people living closer to market centers — where homes were made of manufactured materials including lumber and concrete — had less diverse microbiomes than people in traditional villages farther away. Researchers think the difference could be because the village homes were palm thatch structures with dirt floors, enabling more exposure to microbes from outdoors.

Thriving with different microbes

To understand why microbial diversity — the number of species of bacteria in a person — is important, imagine a forest, said Guillemin. If the forest has many types of plants, it is more likely to survive environmental changes and disease. Similarly, people who have more diverse microbiomes seem to cope better with disturbances such as antibiotic treatment and infections.

Scientists are studying why some people infected with the novel coronavirus have only mild symptoms of covid-19, while others become seriously ill. We know that older age and certain conditions such as diabetes raise the risk of complications, but the health of our microbiomes probably plays a role, too.

“I think it’s very plausible that your microbes are influencing your immune system responses,” Guillemin said.

Good nutrition and microbes

Even though the pandemic has changed our normal routines, we can take steps to keep our microbiomes healthy. Spending more time outdoors whenever possible is a good idea. And the foods we eat can promote a diverse microbial community in our digestive tracts.

What kinds of foods do our microbes like?

“Lots of complex plant material benefits your microbiome,” said Guillemin. When you eat fruits and vegetables, you’re giving your microbes what they need to stay strong.

Microbes are tiny, but just like tigers, elephants and other vulnerable species, many are at risk of extinction. The more we feed our microbes what they need, the more likely it is that they’ll stick with us for a long time.

learn more

You can check out videos about the microbiome at these websites:

“You Are Your Microbes” at bit.ly/33QwNyz, with Karen Guillemin and Jessica Green.

“The Invisible Universe of the Human Microbiome” at bit.ly/35WMLtK, produced by NPR.