Mitochondria: the hidden bacteria that powers your body

Over two billion years ago, a hungry bacterium struck a deal with a primitive being. In exchange for the host not killing it, it would produce infinite energy. A symbiotic friendship of sorts.

The bacteria is called mitochondria.

It powers your body, metabolism, and allows you to run, walk, climb. So much so, that scientists have theorized that the reason we are alive is to enable mitochondria to live.

So how did this relationship develop?

In a fascinating demonstration of the desire to live and flourish, the host cell stripped the mitochondria of DNA. The mitochondria had come with perhaps 1000 genes. After the plunder, it was left with just 37. We call these mtDNA

The rest was absorbed by the host cell. Just in case you are curious, you have approximately 20,000 DNA.

The 37 mtDNA that were left behind were there for a reason. It allowed the mitochondria to play its role, in producing ATP, energy that your body uses to live.

This evolutionary history explains why mtDNA differs fundamentally from your DNA. It’s circular rather than linear, lacks protective proteins, and sits directly in the mitochondrial matrix.

With limited repair mechanisms and high mutation rates, mtDNA is roughly 10-17 times more vulnerable to mutations than nuclear DNA.

Which is why we need to worry about mitochondrial diseases.

Each cell in your body contains hundreds or thousands of mitochondria, each with multiple copies of mtDNA. When mutations accumulate, cells develop a mixture of normal and mutated mitochondrial genomes. The condition is called heteroplasmy.

The organs most vulnerable?

Those with the highest energy demands. Brain, heart, muscles, eyes. A child might appear healthy until the proportion of mutated mtDNA crosses a critical threshold.

Then, symptoms become obvious. Muscle weakness, neurological deterioration, vision loss, cardiac problems, migraine, seizures.

Symptoms are usually the only way to know if you have DNA damage from the mitochondria.

Because mitochondria pass exclusively through the maternal line, these diseases follow unusual inheritance patterns.

A mother carrying mutated mtDNA may have mild symptoms herself but pass it on to her children.

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