♪
(woman)
Microorganisms are small.
So small, you can't 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.
Their resources
and territory are scarce,
and the stakes are survival.
Mold has a powerful
chemical weapon in its arsenal.
I'm Emily.
I'd like to show you Alexander
Fleming's famous discovery
that bread mold
kills bacteria.
Here's some fresh bread.
I'll add some water
because mold loves moisture.
Now I need bacteria,
which you can find
basically anywhere,
including in your mouth.
This Petri dish has
a Jell-O-like layer of agar,
food for bacteria
in my saliva.
It'll take a few days before
the colonies of bacteria
are big enough to see.
Let's set up place
to grow mold and bacteria
in a contained way,
so it doesn't spread
or infect anything else.
These bell jars will make sure
that nothing contaminates
the experiment,
and the experiment doesn't
contaminate anything else.
I'm back.
Wow, there's
a lot of bacteria.
Each cell divided
and divided and divided
to make a colony
that we can see now.
The bread mold also grew.
Let's see if it can
kill some bacteria.
I'll take some bread mold
and let it work.
Legend has it that in
Fleming's original experiment,
some mold from
his lunch sandwich
accidentally dropped
into his Petri dish.
Let's take a closer look,
then we'll come back later
and see what's changed.
Under a microscope,
mold looks like
this yellow model,
and mold attacks
bacteria cell walls,
represented by these cups.
Mold secretes a chemical,
penicillin,
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 see where the bacteria
have died around the mold?
This is called
the ring of death.
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 I,
was the first to realize
how useful antibiotics are
for treating infection.
Today, we remember him for
his discovery of penicillin.
I think his experiment is neat,
and I hope you do too.
♪
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U.S. Department of Education.
