Life without mitochondria

Eukaryotic cells make up all living things, and they almost always have a power-generating organ called the mitochondria – or so we thought. Now, the discovery of a cell without a mitochondria is showing scientists how flexible living organisms can be.

TRANSCRIPT

Eukaryotic cells are what make up you, me, and other living things, and they almost always have a power-generating organ called the mitochondria -- or so we thought.

Now the discovery of a cell without a mitochondria is showing scientists how flexible living organisms can be.

Here's a look.

Anna, thanks for joining us here.

Hey. Hello.

First, can you explain what are eukaryotic cells?

Where can we find them?

What kinds of cells are they?

Oh, eukaryotic cells we can find everywhere.

Of course, we have eukaryotic cells, but also plants and fungi and animals.

Those are the ones which we, most of the time, think about eukaryotes.

When we think eukaryote, we think about big animal, big plant.

But there are also eukaryotes which are single-celled, and there is a lot of them.

A lot of them are parasites, a lot of them in the water.

Some are algae.

So, they could be, like, really small, from single-cell organisms, up to human, elephant, everything what is big, too.

But the main difference with bacteria is that eukaryotic cells has a nucleus, whereas the prokaryotic cell does not.

But, generally, eukaryotic cells are pretty much the same in form and function where we find them?

Yes, although, of course, it's hard to say that human being is the same as yeast, because yeast do everything within one cell, and our cells are diversified.

So each group of cells do a little bit different thing, whereas if the organism is only one cell, the cell has to do pretty much everything for it to fulfill the life.

So, those yeast and those kinds of eukaryotic cells are more self-sustaining.

Yes.

Then, within the cell, we have smaller organs, one of which is the mitochondria.

Can you explain what the mitochondria does?

Right. In eukaryotic cells, as I mentioned, there is a nucleus, but there are also other organelles.

You can define them as small organs, and one of them is mitochondria, which many, many cells -- It's a creator organelle for many cells, eukaryotic cells and the main function in organisms which live in environments when there is a lot of oxygen, so, basically, like we are now, for example.

Okay. Land animals and things like that?

So, the organisms we see most of the time -- they live in environments where there is enough oxygen to use mitochondria for energy generation.

So, that's the function, like, main function we think about when we define mitochondria.

Although, they do also many other things which are important for the cell.

So, the mitochondria brings in oxygen to produce energy?

Well, mitochondria are using oxygen as a part of the process of energy generation.

And that energy fuels the cell to do everything that it needs to do?

Yes.

Now you and your team have discovered a eukaryotic cell that functions without a mitochondria, which seems like a car going without a gas tank.

How did you discover that?

And how does it work?

I mentioned that the organisms which live in environments with oxygen -- they really need mitochondria for the energy generation.

But there are environments where there is less oxygen or almost no oxygen -- for example, our ducts -- where organisms which live there -- they don't use oxygen in energy generation.

And then they don't use mitochondria for the function most of the time.

And we were looking for their mitochondria and how they changed.

We knew before -- I think for the last 30 years -- Scientists working on that and looking on changes in mitochondria which happen when they live in different environments, especially depleted on oxygen.

Mm-hmm.

And they are, of course, different, because they don't do the same as our mitochondria, although they originate from the same -- This is the same organelle still, but very reduced and changed.

Did you question whether this still sort of qualified as a eukaryotic cell?

No, because it has a nucleus.

So, that's the -- The definition is mainly by the nucleus.

It should have, also, other organelles.

Mitochondria is not the only organelle.

There are also other membranes inside the cell, and it has other typical eukaryotic characteristic features.

So, we don't have this eukaryote, just those organisms have different, very divergent mitochondria.

And what does this tell us?

Are we learning any new insights or does this inform any future research?

What I would say, given right now, it's a broader context.

So, there is this group of organisms which have this mitochondria.

But, like, the one we discovered -- the surprise part of the discovery was that it really doesn't have anything left, because so far, every organism which was checked for it and believed, initially, that maybe it doesn't have anything, in the end, scientists were able to identify some remnant mitochondria.

And, in this case, we couldn't find any.

For biology, for evolutionary biology, this is an interesting discovery, because it shows how divergent it could be, eukaryote, how flexible is eukaryotic cell, what is in the organelle which was believed to be indispensable?

And we found out there's some special circumstances it could actually be lost.

Okay. So, a new take on the eukaryotic cell.

Thank you so much, Anna, for joining us.

Thank you.