In 1703, an anonymous Englishman, known to history only as Mr. C,
wrote to the Royal Society of London
to report on a peculiar observation he’d made using only a simple microscope.
He’d been looking at the roots of pond-weed, but as he looked closer, he found attached
to the roots, “‘many pretty branches, compos’d of rectangular oblongs and exact squares.’”
At first, he assumed these geometric attachments must be salt crystals.
But the more he experimented and looked through his microscope, the more he realized there
might be something amazing going on here.
These tiny, beautiful shapes seemed kind of plant-like.
Today, with the benefit of many, many more observations, and far superior equipment,
we know that this 18th century
letter is one of the earliest descriptions of a diatom, a photosynthetic, unicellular
algae that can become so plentiful that oceanic blooms of these organisms, which we cannot
see individually without a microscope, are nonetheless visible from space.
But, we wouldn’t be talking about diatoms if we needed to be in space to observe them.
You can find these tiny organisms just about anywhere that has water and light.
Looking at them through a microscope, you might understand why microbe hunters are so
fond of them.
They have been called “the jewels of the sea”.
Those beautiful outer shells are called frustules, and they set diatoms apart from every other
living creature.
Unlike the organic cell walls and membranes we associate with most cells, frustules are
made out of inorganic silica, enclosing the cytoplasm of the diatom in, what is basically, glass.
Silica shells take less energy to make and maintain compared to their organic counterparts,
but they do come with a trade-off.
Glass is…well, it’s glass.
It’s hard to expand if you’re a unicellular organism trying to undergo asexual mitosis
when your cell is inclosed in a rigid, inorganic material.
Instead, when diatoms divide, the daughter cells take the old frustule and divide it
between them, which means that the daughter cells are both going to be smaller than their
parent, and they’re never going to grow any bigger.
And as diatoms keep dividing, the daughter cells keep getting smaller and smaller.
If this goes on forever, the diatom will get so small that it cannot survive.
But diatoms that are starting to get too small can avoid that fate through sexual reproduction,
which is kind of a refresh button that lets them construct a new frustule for a larger
daughter cell.
For the most part, diatoms can’t actually move—they just go wherever the water takes them.
But some diatoms are able to glide along a surface using a slit in their frustule called a raphe.
This allows them to secrete mucus that sticks to a surface but,
how does that mucus help them move?
We...don’t know.
We can see that they move, so they must be able to
And we can see that mucus is always left behind when they do it,
but we don't know the exact mechanism of how it works.
You and I, of course, move using muscles.
And the moluecules responsible for that in us are actin and myosin.
Here’s a wild thing, in 1999 some scientists put actin disrupting compounds
in solution with diatoms and those diatoms lost their ability to move.
So while diatom motility remains something of a mystery, these tiny, jewel-encrusted
algae move using the same molecular systems as us.
If you've been looking closely,
you might be wondering what these bubbles are,
and if you are we hope we can surprise you.
Those are oil droplets, and they store energy for the diatom when they might be having
trouble finding light or their usual nutrients.
These little organisms are so good at creating this fatty oil that scientists have wondered
whether we might use diatoms as tiny factories that turn sunlight and carbondioxide into
fuel not just for them, but for our future airplanes.
It might be tempting to think of these cells just as little microscopic jewels, just something
nice to look at, but they also have a huge impact on our world.
Of all of the photosynthesis being done on Earth, around 1/5 is done by diatoms, which puts
them on par with all rainforests on earth combined.
and it means we owe a great deal to these microorganisms.
And not just our oxygen,
when they die, their silica frustules sink to the bottom of the water that they're in
and accumulate into a soft, chalky rock that we know better diatomaceous earth.
That key ingredient in beer and wine filtration, paint, and of course, cat litter.
So, yes, these beatufiul jewels that the unknown Mr. C spotted in 1703 don’t just provide us
with every fifth breath we take, they also help make our cat litter more absorbent.
And also, they’re just really nice to look at.
So thank you for coming on this journey with us as we explore the unseen world that surrounds us.
If you want to see more from our Master of Microscopes, James
check out Jam and Germs on Instagram.
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