Welcome to the Bacteriosphere

Bacteria are a lot more sophisticated than many people think, and —we also owe them our lives. Meet some of these clever, collaborative, microscopic communities that humans depend on

TEXT—Gabrielle Anctil

Are humans the smartest species on earth? I like to think that the answer may be “no.” It might be because I spent much of my youth reading science fiction, but in my imagination, super-intelligent beings are usually bigger than us: malevolent creatures sneakily pulling the world’s strings.

But I’ve been imagining it (almost) all wrong, says Predrag Slijepčević, professor of biology at Brunel University London, who has his own candidate to put forward for smartest creature on the planet. They’re most definitely not bigger than us, nor are they malevolent exactly, but they are absolutely sneaky. These resourceful organisms can survive on the ocean floor and in acidic hot springs. They lurk on the surface of our skin and contribute to our intestinal flora. In fact, they are our intestinal flora.

Perhaps the beings that deserve the top prize in intelligence are—as you’ll have guessed by now—bacteria.

There are few things as humbling as learning about these single-celled organisms, which, long before the ancestors of our ancestors appeared on the planet, had already solved problems still plaguing humans today.

Microbe ecosystems and bacterial communication


Divide one millimetre by a thousand and you’ll have the average width of a bacterium, around one to two micrometres. But don’t be fooled by their size. It’s thanks to them and their single-celled cousins from the closely related domain of Archaea that the entire biosphere exists: all living organisms and their environments.

“Everything started with the invisible engineers: bacteria,” writes Slijepčević in his book, Biocivilisations: A New Look at the Science of Life. Three-and-a-half billion years ago, earth was rather calm, until single-celled organisms discovered the sweetness of the sun through the process of photosynthesis. Gradually, over a long period of time, photosynthesis generated enough oxygen in earth’s atmosphere to sustain other life forms.

But bacteria didn’t stop there. They’ve established themselves all across the world, finding their niches in every ecosystem, including the most hostile environments. These tiny globetrotters have even developed ways of talking to each other over vast distances.

“In theory, a signal emitted by bacteria in waters around the South Pole could travel almost instantaneously to bacteria in the waters around the North Pole,” explains Slijepčević.


Let’s sit with that fact for a second. Bacteria cover the entire planet. According to one peer-reviewed study published in 2019, they number 1.2 quintillion: that’s a 12 followed by 29 zeros. There are 400 trillion of them in each human being by Slijepčević’s estimate, meaning that there are as many bacterial cells as human cells in our bodies. It’s enough to make you dizzy.

As miniscule as they are, bacteria communicate with each other, vote, carry out genetic experiments, and cleverly adapt to environmental pressures. They also come together to create bacterial “cities,” which scientists call biofilms.

This ability to structure themselves fascinates Chloé Savard, a microbiologist known as “Tardibabe” on social media: “[Biofilms] are places where bacteria can reproduce, feed, and live. For example, they’ll create channels for waste. They’re little micro-societies.” Biofilms can form in various unlikely places, including your teeth: dental plaque is a classic example.

In short, bacteria—like the rest of us—thrive when they help each other out.

Human symbiosis with the bacterial world


The truth is that we need bacteria more than they need us. They have been surviving planetary upheavals since long before humans existed. But the even deeper truth is that there is no “us” and “them” in the bacterial world. Our bodies constitute entire ecosystems where bacteria flourish.

“The bacteria that live in our bodies could survive in nature,” says Savard, “but we’re generally their preferred environment.”


Forget about competition: together, we form a complex entity. Wherever we go, so do our bacterial flora. “We’re never truly alone,” as Savard philosophically puts it. Bacteria offer us a powerful lesson in humility: it’s thanks to these tiny organisms that we’re part of a select group—life on planet earth.




Contrary to popular belief, most bacteria are not all good or all bad. With the help of microbiologist Chloé Savard—who goes by “Tardibabe” on social media—Gabrielle Anctil presents five fascinating micro-organisms that live in the human body. 

TEXT Gabrielle Anctil
IMAGES Chloé Savard


What’s the secret ingredient in your breakfast yogurt? Your miso? Or just about any probiotic? That would be Lactobacillus! These rod-shaped bacteria, which aptly resemble pills, travel to your intestines and help care for them. They thrive on carbohydrates. Our faithful friends, the ubiquitous Lactobacilli are essential for our health and live in our bodies’ mucous membranes—in the human mouth, digestive tract, and vagina.

Escherichia coli

Escherichia coli doesn’t have the best reputation, and for good reason: some strains of this bacteria can wreak havoc on our bodies and even cause death. Luckily, most strains are harmless, and handwashing and adding chlorine to drinking water are two easy ways to neutralize this bacterium. E. coli rarely exists alone, and researchers use it to test for the presence of other micro-organisms that are more difficult to detect. But let’s also give credit where it’s due: E. coli plays an essential role in our bodies, producing vitamin K and preventing pathogenic bacteria from colonizing our intestines.


This little Y-shaped bacterium is one of the first to colonize our digestive tracts after birth. It helps us out in so many ways, including by facilitating the digestion of some fibres and producing vitamins and antimicrobial agents. Nearly 50 species of Bifidobacterium have been identified, and each one has a distinct benefit for our health. And despite all they do, they make up just 10 per cent of the bacteria present in our gut … Clearly, these guys are hard workers.

Staphylococcus epidermidis

Our gut microbiome has received a lot of attention in recent years, but it’s not the only microbiome in the human body that deserves some love. Staphylococcus epidermidis colonizes our entire skin; these spherical bacteria form grape-like clusters and help protect our epidermis. What’s not to like about that? Well, there is one thing … If you spend a long time in the hospital or receive a surgical implant (for example, an IV), these bacteria may enter your bloodstream. And that’s where the problems start, as Staphylococcus epidermidis will form biofilms (those bacterial “cities” mentioned above) that increase their resistance to antibiotics.


Prevotella are unassuming bacteria that live comfortably on human skin, in the vagina, and in our intestines, as well as elsewhere in the environment. But they reign supreme in our mouths. Studies have shown that Prevotella are especially abundant in rural populations with a pre-industrial lifestyle. Though they have received less attention from the scientific community than other bacteria that live on our bodies, Prevotella deserve further research, as their diminished presence in industrialized societies may have real health impacts.

Gabrielle Anctil is an independent journalist. You can hear her on Moteur de Recherche, read her words in Québec Science, BESIDE, and Continuité, and see her on Bataille pour la Forêt (Savoir Média). She is the author of Loger à la Même Adresse, an essay published by XYZ. All year round, she can be found beaming on her bicycle.

Chloé Savard is a Montréal microbiologist with a background in music who discovered the world of microscopy only three years ago. Under the moniker @tardibabe on Instagram, Tiktok, and YouTube, she transforms things and beings imperceptible to our naked eye into works of art, while raising public awareness of the fragility of these tiny ecosystems.

Share if you liked this story

Never Miss Another Issue

Two issues per year

25% OFF previous issues

Free Shipping in Canada

Newsletter Signup

To receive the latest news and dispatches, subscribe to our newsletter.