Previous: Diatoms: Tiny Factories You Can See From Space
Next: How Do Colonies Help Microorganisms Survive?



View count:454,107
Last sync:2024-01-30 14:30
When you peer into the microcosmos, it’s sometimes hard to see past the cells themselves.

Flitting around, fighting, surviving, movement and shapes and colors. But we can see deeper, and there is so much to see if you look beyond that first level, and into the cell itself.

In the cytoplasm, mysteries and curiosities abound. Here in our macro-world, to see inside an organism we need expensive scans or exploratory surgeries. In the microcosmos, we can just turn on the light and see some of the bizarre and beautiful systems that these organisms have for increasing their chances of surviving a harsh and uncertain world.

So let’s take a look at some of the structures inside of cells that you may have never heard of, and that we love to let blow our minds. This is the unicellular alga Closterium. And at the very tips of the cells, an alluring little object.

Do you see that orb with the tiny round things inside? Those are actual crystals made of barium and calcium sulfate. But why are they there?

Well, no one knows yet, and we hope...nay we know... someone will someday solve this mystery. But for now, it is yet another thing that we do not know about our universe. These crystals are extremely small.

Around two to three microns across. If you divided a millimeter into 500 equal pieces, one of those pieces is how big those little grains are. But there’s more.

You see how those crystals jiggle around and never stop moving, even though nothing seems to be moving them. Well, one thing we know about the universe is that things don’t just move….the energy has to be coming from somewhere. Let’s remember that everything you're looking at here is made of atoms.

And when two hydrogen atoms and one oxygen atom come together, they form a water molecule. Now, Closterium lives in water, which means it's surrounded by and filled with water molecules. And they are in constant motion, that’s what heat is.

The movement of atoms and molecules. If they weren’t moving at all, that would be absolute zero. -273.15 degrees Celcius. That's not where we're at.

These water molecules are moving around a lot and they're bumping into everything and they can even move objects around. But if something is really big, like a whole Closterium cell, you can't actually see any movement. But since these crystals are tiny, the water molecules visibly toss them around.

This dancing is called Brownian motion, and we love it because we of course cannot see water molecules under the microscope, but we can observe their effect on these crystals. Indeed, Albert Einstein used Brownian motion to confirm that atoms and molecules exist which, in 1905 when he published his paper on the subject, was still a matter of debate! And now, we’re watching it happen...watching water molecules smashing around into crystals that, as yet, remain unexplained, but must have some reason to exist besides being fun for us to look at.

This is Nasulla ornata, a beautiful unicellular ciliate. Although it doesn’t look like it right now, they can move quite fast. But what you are looking at is a squashed Nassula ornata.

We decided to give it a bit of a squeeze so we could take a real good look. When Nassula ornata hunts for food,. It prefers filamentous cyanobacteria or algae.

It wraps its membrane around it, forming a food vacuole. As it continues to eat it forms more and more of these vacuoles. Now, what's so nice about them are their colors.

Cyanobacteria and algae, Nassula’s food, are green, but when Nassula starts dumping digestive enzymes into these food vacuoles, a chemical reaction occurs changing the color of the food vacuole over time. Because different vacuoles are at different stages of digestion, each vacuole is a slightly different color, giving this ciliate its beautiful, colored polka dots. These are the very long, very skinny cells of the filamentous sulfur bacteria Beggiatoa.

You can find them all over the globe living in habitats from marine caves to sulfur springs to everyday ponds and rivers. When we find them, they are usually on freshwater pond sediments or decomposing organic material. Beggiatoa excretes mucus, which allows them to glide around on the sediments.

Beggiatoa prefers sulfur-rich environments because they oxidize hydrogen sulfide as an energy source. The hydrogen is used by the organism in chemical synthesis, and the sulfur is left over. Every one of those tiny black dots that you see is a granule of inorganic sulfur.

Here’s another clip where you can look at them a bit closer under 1000 times magnification. Which, for the moment, is about as good as we can do here. Now, what’s happening here...these little bubbles forming and popping...well they are not bubbles of air, they’re bubbles of pure water.

One of the most fundamental structures for life as a freshwater single-celled organism is the contractile vacuole. This organelle allows unicellular organisms to pump excess water from their cell. Why?

Well, Inside of every cell, there are a lot of dissolved substances—more than the surrounding water contains, certainly. Whenever there is an imbalance like this, things tend toward equilibrium. And the only thing separating these cells from the water around them is a membrane that allows some, but not all substances to pass through it passively.

One of those substances is water. When the concentration of stuff inside the cell is higher than the concentration of stuff outside, water diffuses into the cell. There is no way to stop this diffusion.

The solution to this constant influx of water is the contractile vacuole. This organelle fights a continuous battle, pumping and pumping and pumping the water out. Imagine, though, if the contractile vacuole was not working.

You might think that, eventually, the cell would fill with so much water that the cellular machinery might break down. Well, maybe, except, before that happened, the cell would expand so much that its membrane would break and it would literally explode. So, y’know, good job little vacuole.

The ciliate Loxodes is a common resident of different aquatic habitats, but they prefer a distinct zone in the water. A “Goldilocks” zone for oxygen. They like concentration not to be too high and not too low.

And in a body water, unless something weird is going on, the oxygen concentration is higher at the top and lower toward the bottom. Because of its specific oxygen concentration preference, Loxodes needs to know which way is up and which way is down so it can find just the right spot. But how could a single celled organism know up from down?

Well, Loxodes can sense gravity! It has organelles called Müller vesicles that each contain a spherical mineral granule—the. Müller body—attached to a hair-like cilium.

Sorry these friends zip around so quick, it can be hard to get a good look. These granules, the Müller bodies are actually pulled down by gravity, and it is believed that this “pulling” causes sensory signals to be transmitted to the cell through the cilium. So, Loxodes, despite being tiny and despite being just a single cell, has an organ very much like our inner ear, allowing it to sense up from down.

So yes, microbes display quite the collection of intracellular structures! Only a few of which we discussed here. Some shiny, some colorful, and some that provide fascinating advanced capabilities.

And it makes us wonder, what other structures are yet to be discovered? There is so much that we do not know. We hope to report back to you on this question because we are sure that there are many more out there just waiting to be unveiled by a discerning eye peering into the microcosmos.

If you want to see more from our Master of Microscopes, James check out Jam and Germs on Instagram. And if you want to see more from us here at Journey to the Microcosmos,. I bet there's a subscribe button somewhere nearby.