Living in a microbial world

The non-humans parts of our body are called our microbiota. (Gyrd Harstad/Creative Commons Flickr)

The Research column will be a weekly feature on the scientific opportunities on campus written by staff writer Diler Haji.

An estimated 90 percent of the human body isn’t human. In the gut alone, there are nearly 10,000 species of bacteria and another 5,000 living on the skin. They can be anything from bacteria, viruses, fungi and microscopic mites to less recognizable microbes like protozoans and archaeans.

The non-human parts of ourselves, called our “microbiota,” have fueled a radical new way of thinking about multicellular life on Earth. They're helping us understand how life evolved from relatively simple cells floating in the ocean, to the complex beings we call Homo sapiens. 

Each of us is a holobiont, a composition of many different species that create an individual. 

It’s no surprise that former President Barack Obama unveiled the National Microbiome Initiative just last year. (The term “microbiome” is often used interchangeably with microbiota.)

The plan is to invest nearly half a billion dollars into the tiny communities that inhabit not just humans, but every multicellular creature on this planet. While the current administration and political climate may endanger the initiative, there is no doubt that science is still moving forward, equipped with new technologies to explore the microbial world like never before. 

Here are just a few examples of just how important microbiota are:

Ironically, the beneficial bacteria living within us enhance our immune response against bacteria that sicken us.

Research has linked our microbiota with everything, from diseases like autism to obesity, and even our changing moods. The choices you make every day — what you decide to eat or the environments you surround yourself with — changes the composition of your microbiota, which could have all sorts of effects throughout your life.

When it comes to behavior, microbiota have been shown to increase “bravery” by interacting with the brain through your blood. For example, mice given a dose of microbes increase their activity and curiosity compared to mice without those microbes. 

Ann O’Hara and Fergus Shanahan, researchers at the National University of Ireland, call microbiota the “Forgotten Organ.” 

It’s well known that breast-feeding, for example, builds up the microbiota of a baby as the baby develops. Just by going vegan, you can change the community of microorganisms living in your gut too.

One of the most amazing aspects of microbial life (particularly bacteria) is that they can swap genes. This is how bacteria often gain resistance to our antibiotics. On the other hand, they can gain a gene that allows their hosts (humans) to gain an ability they otherwise wouldn’t have. 

The most famous example comes from the Asia, where coastal communities have eaten seaweed for centuries — and a special type of bacteria that live on seaweed called Zobellia galactanivorans.

Coastal people have been eating Z. galactanivorans with their raw seaweed for so long that it transferred a gene to the bacteria living within them. Today, that gene allows many Easterners to digest seaweed while the Western world cannot. 

It’s almost like gaining a superpower!

Microbiota are changing the way we think about evolution too. If microbiota can give organisms the ability to exploit new food sources or survive in new environments, they could be a key force driving diversity on Earth. Insects are increasingly becoming models in helping us understand our own microbiota. 

Humans are complex and so are their microbes. Insects, on the other hand, are a lot less complex and could provide us with key discoveries. 

Without their microbes, many insects would go hungry. Plants often don’t provide the nutrition that insects need to grow into adulthood, so microbes living within them synthesize those missing nutrients.

One of the most amazing cases of the intricate relationship between microbes and insects comes in the form of a tiny mealybug that sucks on sap from leaves. 

Plannococcus citri is locked in an inseparable “triple” relationship – a symbiosis.

Inside of P. citri lives a bacterium called Tremblaya and within Tremblaya lives another bacterium called Maronella — think of a Russian nesting doll. 

Each member of the symbiosis produces nutrients the others can't make. Without all three of them, P. citri would be short of the essential nutrients it needs to live and the whole system would collapse.

Wherever microbiota take us, they are likely to unveil aspects of human health and nature that were inaccessible until now.

Generally, people view microbes as evil creatures that spread disease and kill, but they are a fundamental part of what gives us life. After all, bacteria were living on Earth nearly 2.5 billion years before the first humans.


Diler Haji is a staff writer for The Daily Campus. He can be reached via email at diler.haji@uconn.edu.