We are just a symbiotic collaborating bacteria: Why You Are a Bacterial Supergroup in a Tracksuit

If you’ve ever fancied yourself as a lone individual, an autonomous unit of decision-making brilliance, don’t. You may not realise it, but you are not a singular being. You’re a walking parliament of cellular delegates, a confederacy of semi-autonomous microbial citizens with different accents and job descriptions, duct-taped together by evolution and trying their best not to collapse into chaos. If anything, you’re three million toddlers in a trench coat trying to drive a bus through rush hour traffic, and everyone thinks they are in charge of ATP production. Like a stack of toddlers in an adult jacket, it is a miracle that you coordinate enough to move in the same direction.

Let us begin at the beginning, or at the beginning of you. And by “you,” I mean the system of systems, the bus of passengers, and the fleshy ensemble cast that makes up the human body. At the cellular level, the mitochondrion is the most iconic example of reluctant cooperation. According to the endosymbiosis theory, these sausage-shaped powerhouses were once free-living bacteria, toughing it out in the primeval sludge some 1.5 to 2 billion years ago, long before any cell dared to call itself “complex.”

Somewhere along the line, one of these ancient bacteria got slurped up by a larger cell. This primitive eukaryote either lacked a good immune response or had read How to Make Friends and Influence Prokaryotes. Rather than digesting the little intruder, the host cell decided to keep it for reasons still unclear. Perhaps it was a case of Stockholm syndrome at the cellular level. Or maybe it was just easier than cooking dinner.

Whatever the case, the internal bacterium struck a deal: it would pump out adenosine triphosphate (ATP) with industrial zeal, if only the host cell would feed it and keep the predators away. Over time, this bacterial houseguest streamlined its operations—shedding genes like a backpacker ditching spare socks—until it could no longer live independently. It became wholly dependent on the host cell, just as the host cell became addicted to its bottomless energy buffet.

This wasn’t a merger. It was a hostile cohabitation that turned into biological codependency. And every single one of your cells still bears the legacy of this forced marriage: the mitochondria, tirelessly manufacturing energy while nursing a grudge about the independence they once had.

And, lest you think this tale is unique, it isn’t. Chloroplasts, the green-glowing organelles in plants, have the same origin story. Life is nothing if not a repeat of the same messy romance: a bigger organism eats a smaller one, doesn’t finish the meal, and then writes a prenup.

After mitochondria moved in, things got weirdly organised. Some eukaryotes—probably tired of being blobs—decided that sticking together was a good idea. This marked another evolution’s “major transitions,” which John Maynard Smith and Eörs Szathmáry catalogued with nerdy delight: multicellularity.

But like every flat-share or startup, somebody had to clean the dishes, and someone else got to keep the equity. In biological terms, the germ got reproductive rights, while the soma did the work. Your muscles, eyes, brain, and spleen? That’s all soma genetically identical to your sperm or eggs, but tragically non-transferable. You are, biologically speaking, a meat puppet designed to carry your reproductive cells to the nearest candlelit opportunity.

This division only works because the soma and the germline cells are clones, derivatives of the same original zygote, and evolutionarily aligned. It’s like a corporate structure where the warehouse and the C-suite share the same DNA, so there’s no real mutiny. Yet.

There’s something disturbingly poignant in this: the idea that everything you think you are, the ego, the ambitions, the curated Spotify playlists, is a grand support staff for your gametes. We are all but delivery systems for the next generation’s genetic USB stick. Of course, cooperation isn’t unique to big, multicellular show-offs like us. Even bacteria, those tiny, underslept pioneers of evolution, get in on the action.

Take Pseudomonas aeruginosa, a bacterium best known for infecting the immunocompromised and starring in academic papers. In a 2022 study from Oxford University’s Department of Biology, researchers discovered that these bacteria cooperate by sharing resources, particularly iron-scavenging molecules known as “public goods.” Like humans pooling resources to build a dam, bacteria collectively release siderophores into their environment to extract iron from their surroundings.

This is where it gets spicy. The cooperation only makes sense if the benefits stay primarily within the family, i.e., other closely related bacteria. This is kin selection at its purest: bacteria helping their brethren, because helping someone 99.9% genetically identical to you is almost as good as helping yourself.

The Oxford study didn’t just look at behaviour; watching bacteria is like tracking toddlers through a keyhole. Instead, they examined genetic signatures, looking for patterns in DNA sequences from wild strains of P. aeruginosa. Sure enough, the cooperation genes were highly divergent from their ancestors and had lots of genetic variability—classic signs that these genes are under selection pressure to spread in kinship-based settings.

In other words, bacteria aren’t just blobby solo acts. They are whispering to each other across evolutionary time, forging alliances, making trade-offs, and cooperating when it pays off. And, yes, they do it in clinical settings too—those pathogens infecting you? They’re working as a team.

The Democratic Illusion of the Self. When you zoom out, the human body looks suspiciously like a scaled-up version of these bacterial collaborations. You’re a vast, squishy biofilm with better credit. Your cells are genetically related and willing to play nice, for now. You have mitochondria that are just outsourced bacteria. You house trillions of actual bacteria in your gut who aren’t genetically related but still cooperate (so long as you don’t get cocky with antibiotics).

You are not a “self” in the tidy Cartesian sense. You are a biological commons, a temporary ceasefire, a weirdly well-dressed echo of endosymbiotic events and microbial kin selection, wandering through space-time and wondering why the Wi-Fi is so bad in the guest room.

Maybe that’s not such a bad thing to remember the next time you feel a little disconnected because you’re never really alone.

You’re a collective.

A messy, mitochondria-powered, genome-sharing, iron-harvesting, cooperation experiment that somehow woke up and decided to write poetry.

And frankly, that’s the most astonishing evolutionary outcome of all.