Symbiogenesis — Reflections on Biology and Medicine

THE GREAT CELLULAR JOURNEY

I still remember with horror the scene where an alien parasite invades the host and turns the poor victim into a zombie-like puppet. Although I am well aware that this is just a movie, there is something about the whole setup that sends a literal shiver down my spine. Similar story when the roles are reversed and human recklessness leads the protagonist to enter a foreign entity into its lair, thinking that he could control and make it dance to his tune - only for the story to flip on its head.

Imagine my fascination-stricken aghast expression when I first learnt that this fiction indeed seems to be true to its core. Enter the world of symbiogenesis.

Lynn Margulis, an American evolutionary biologist, was at the forefront of this paradigm-transformative theory in the 1960s. Symbiogenesis is the process by which a long-term mutually beneficial partnership - or symbiosis - eventually leads to a permanent new feature such as an organ, metabolic pathway, or function.

Billions of years ago, two such organisms formed the proverbial pact and fused together for eternal iteration. A bacterium engulfed in the house of a prototype prokaryote. For reasons unknown, the bacterium wasn’t digested to smithereens but persisted in defiance. The arrangement was simple - each retained its own integrity via its respective genetic blueprint, whilst at the same time shared a common metabolic metasystem housed within the same solid structure.

Enter the humble human cell and its mitochondria. One represents identity; the other, energy. One the superstructure; the other, the powerhouse. Perhaps this represented the ultimate game theory solution amongst stable replicators in the then still relatively primordial soup. Sacrifice each other’s distinct originality for a promised future of infinite replicability and acceptable fidelity.

Now this has got me thinking… and I’m off to watch the next alien movie on Netflix.

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