Do you usually help your friends when they need something from you?

(I hope you do, as this is just good practice)

But just as we would always give our friends help when they need it, so do bacteria help each other or share food with each other when they know one of them is struggling.

How they do that?

Read on to find out how.

Two bacterial cells can form special tubes between them to exchange cellular content. These tubes are called nanotubes and bacteria use them to exchange nutrients to ensure the receiving cell survives.

How bacteria make stuff

First let me explain the concept of proteins.

DNA is transcribed and translated into peptide chains made of amino acids. This folds into an active protein.

The DNA of a cell is transcribed and translated into chains of amino acids. This chain is called a peptide. This peptide folds into an active protein.

There are twenty amino acids. Hence, proteins can have all sorts of different shapes, sizes, functions, you name it. Proteins are present in every cell and are responsible for the functioning of EVERY living cell.

Now, the amino acids are like LEGO bricks that can be linked together in a million different ways and the outcome is always different (which is why proteins are so different). To produce all the essential proteins, each amino acid needs to be present within a cell.

Some organisms can produce certain amino acids, the other amino acids they need to find in the environment to survive

How bacteria feed each other

In this study, researchers used the idea that bacteria need all of the amino acids to survive. To show that two different bacterial strains can help each other out with certain amino acids, they made two kinds of strains:

one strain produced a lot of amino acid W and no H

the other produced a lot of amino acid H and no W

The experimental setup to study how bacteria feed each other.

W and H are the one letter codes for the two amino acids Tryptophane and Histidine.

In the experiments they grew the bacteria in a medium that did not contain the amino acids W or H, but all the other ones. They grew the bacteria:

together so that they would be in close contact

together but with a separating “wall”

on their own

Neither of them could survive on their own as each was missing one amino acid.

When they were grown in presence of a wall none of them survived.

Interestingly, only when they were closely grown together, both bacteria survived. This meant that they needed to have direct contact with each other to survive and their survival completely depended on each other.

Bacteria form nanotubes

When they then took a closer look at the bacteria, the scientists saw that the bacteria formed some kind of tubes between the cells to exchange nutrients.

Bacteria form nanotubes. Figure adapted from Pande et al., 2015

It is as if you and your neighbour both want to make a cake but he misses the eggs and bought too much flour while you forgot to buy flour and got too many eggs. Neither of you would be able to make cake on your own. So you need to dig a tunnel between your flats to exchange eggs and flour and you can both bake your cake.

However, now the interesting question one might ask is how do you know that your neighbour needs eggs and how does he know that you have enough to share? You cannot just start digging a tunnel hoping that your neighbour has the things you need?

So how does one bacterium know that the other one is in need of a certain amino acid? They certainly will not call each other or send the other guy a message on WhatsApp…

And also, what is it that the bacteria actually exchange? Do they send the amino acid itself (hence the eggs) or do they send the DNA so that the other cell can learn how to make the amino acid itself? This would mean you send your neighbour a chicken so he can produce his own eggs… These are the interesting questions scientists keep asking and will hopefully find some answers to soon.

Take away from this week