Name: Bread Mold Kills Bacteria
Uploaded: 2013-02-04T02:09:33.000Z
Duration: 3 min 3 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Microorganisms are small.  So small you can't even see them unless they cluster together.

Each of these dots is really millions of bacteria.

But down at a microscopic scale, mold and bacteria fight vicious battles.

Mold has a powerful chemical weapon in its arsenal.

I'm Emily, and I'd like to show you Alexander Fleming's famous

discovery that bread mold kills bacteria.

I'll add some water because mold loves moisture.

Now I need bacteria, which you can find basically anywhere,

This petri dish has a jello-like layer of agar:

It'll take a few days before the colonies of bacteria are big enough to see.

Let's set up a place to grow the mold and bacteria in a contained way, so it doesn't spread or infect anything else.

and the experiment doesn't  contaminate anything else.

Each cell divided and divided and divided to make a colony

I'll take a chunk of bread mold and let it do its work.

Legend has it that in Fleming's original experiment,

some mold from his lunch sandwich accidentally dropped into his petri dish.

and we'll come back later and see what's changed.

Under a microscope mold looks something like this yellow model,

and mold attacks bacteria cell walls,  represented by these cups.

which damages bacteria cell walls,  stamping out the competition.

This means the bacteria surrounding the mold will die.

We're looking for bacterial death around the mold.

Do you see where the bacteria have died around the mold?

Mold and bacteria have been battling for millions of years.

Mold keeps coming up with new weapons: antibiotics;

and bacteria keeps coming up with new shields: resistance.

Alexander Fleming, after treating wounded soldiers in World War One, was the first person

to realize how useful antibiotics are for treating infection.

Today we remember him for his discovery of penicillin.

I think his experiment is really neat, and I hope you do, too.