By Brannen Basham

The natural world is a well-worn battlefield, filled to the brim with an almost endless supply of organisms each vying for survival. In many ways, humans have managed to free ourselves from this constant struggle.

Modern humans are generally not forced to fight for food, shelter and their lives in the ways our ancestors did. Although this is true, fierce battles are still waged around, on, and even inside our bodies on a microscopic scale.

Microorganisms such as bacteria, fungi and viruses assault our bodies at every opportunity, seeking to colonize our flesh and spread to others. The human body relies on a complex immune system built of multiple layers to repel most of these attacks, however our body does not work alone.

Instead, we actually harbor populations of specific microorganisms that help in our defense as well. Microorganisms take up residence all over the human body, but have the highest populations on our skin, in our mouths, and inside of our digestive system. In fact, these tiny tenants make up a large amount of our bodies and form the basis for several key bodily functions.

Scientists believe that there are at least as many symbiotic microbial cells involved in the human-machine as there are actual human cells. This is important to visualize – at least half of the cells in our bodies are not human. We are quite literally walking ecosystems, containing hundreds or even thousands of species of microorganisms at any given time.

Most of these organisms are bacteria, who find shelter in nooks and crannies on and inside our bodies that offer a comfortable temperature along with food and water. This tends to be places like the mouth and gut, however our skin is also covered with microscopic colonies as well. While bacteria make up most of the population, other microorganisms such as viruses and fungi also play important roles. Interestingly many of these microscopic residents will establish themselves in specific areas of the body.

Studies have shown that many of the microorganisms found in the human body are different than those found in the wild – it seems that as humans have evolved over millions of years, certain microorganisms also evolved to take advantage of living in close proximity to them. We are normally passed down a collection of beneficial organisms from our mothers at birth, and these populations appear to change over time as we age, change diets and become introduced to bacterial stressors like antibiotics.

The microorganisms on and in our bodies are always fighting their neighbors in order to secure the best turf, and an equilibrium is eventually reached wherein distinct patches grow into microscopic cities of sorts.

These tiny organisms do not get a free ride, however. Research is beginning to show that the host of microorganisms living with us can help us live happier and healthier lives. It might sound strange, but bustling populations of microorganisms on our skin and in our mouths can be a great defense against illness. Any harmful agent that lands in such a location will find itself dropped in the middle of a powerful enemy, to be quickly destroyed by the resident hitchhiker. The microorganisms in our guts aid our bodies in digesting foods and vitamins that would otherwise be unusable. Some scientists even believe that there is a close relationship between the types of resident microbes in our bodies and the functioning of our immune systems.

We still know very little about the lasting effects that symbiotic microorganisms have on our bodies, however it is clear that at the very least, our bodies perform their best with a little micro-assistance.

Brannen Basham and his wife, Jill Jacobs, operate Spriggly’s Beescaping, a business dedicated to the preservation of pollinators. He can be reached at