[intro music] ED YONG: This is one of the great disruptors of the modern era.

This changed everything.

Before this, child birth, getting a tooth pulled, even just a scratch could have been a death sentence.

Antibiotics-- there are many varieties, streptomycin, erythromycin, doxycycline,cephalosporin, amoxicillin.

But they all share a commonpurpose to eliminate bacteria.

They are weapons produced by microbes to kill other microbes.

Antibiotics are natural substances that have been in use for billions of years.

But humans only tappedinto this ancient arsenal in 1928 and by accident.

On returning to his lab froma holiday in the country, British chemist Alexander Fleming noticed that a mold had landed in one of his bacterial cultures and had carved out a kill zone of slaughtered bacteria around it.

And from that mold, Fleming isolated the chemical that was killing the bacteria.

He called it penicillin.

Penicillin was among the first antibiotics to revolutionize medicine andit saved millions of lives from infections from war, fromsurgery, eating a bad oyster, scraping your knee.

In fact, the need for penicillin was so great and the supply of it sosmall that patient's urine was filtered to extract the unused portion.

Bacteria, the vast majority of them in some where like your gut aren't doing you any harm and many are beneficial.

But most commercial antibioticsare shock and awe weapons.

[bomb dropping] The antibiotic may havekilled off the bad bacteria, but it also destroyed manyof the other microbes living in the gut.

That rich, diverse, microbiome crowds out more malevolent microbes.

Salmonella, campylobacter-- terrible cramps-- clostridium difficile or C. Diff-- crippling diarrhea, 30,000 deaths a year.

It just makes you want to usemore and more antibiotics-- kill, kill, kill!

The problem with antibiotics is not in their use, but in their misuse and thatcreates a second problem.

You probably heard about invincible super bugs.

Bacteria that have evolved to resist antibiotics.

Well, 3 scientists, Michael Baym, Tami Lieberman and Roy Kishony figured outhow to watch that happen.

The first thing they dois to build a petri dish, but a giant petri dish-- about 100 times bigger than the one Fleming used when he came across penicillin.

They call it The Mega-Plate.

They prepare a nutritious agarjelly that bacteria thrive in, but they've snuck a secret weapon into this agar, antibiotics.

They pour it into nine separate bands, each with differentconcentrations of antibiotic.

Then they start growing bacteria, E. coli.

On the outside bands, there'sno antibiotic, just the agar.

The next bands in have justenough antibiotic to kill most E. coli.

Inside those, 10 times as much, then 100 times, and finally the center band has1,000 times as much antibiotic.

On day one you can see E.coli reproducing just fine in the area with no antibiotic, up until they reach theborder with the one times zone where they normally can't survive.

But then a mutant strain appears.

It has evolved a way to avoid being poisoned and it spreads until itreaches the next boundary with the 10 times zone.

Now, new mutants with even stronger resistance begin to spread across the 100 times zone.

And then finally, the hardiest E. coli mutants of all make it into the 1,000 times zone.

And the time it took forthis population of E. coli to evolve this super resistance-- 11 days.

When we watch the plate, really we're watching evolution happening at warp speed.

One of the reasons for thatis that bacteria reproduce much faster than we can.

E. coli can divide in as few as 20 minutes.

So here's a family treethat shows the relationships between the strains onthe plate and it shows us how resistance to antibiotics evolves.

Over the course of 11 days, this strain continued to acquire mutations that made it ever more resistantto the antibiotic all the way to the 1,000 band.

[ding] But this one did not.

[buzzer] When bacteria are exposed to antibiotics, those with mutations that allowthem to survive the attacks are the only ones left standing.

And when those mutant microbes reproduce, and they create a population of super resistant bugs.

So what's happening on the plateis a really good illustration of what's happening at a much larger scale all around the world.

And it's not just when weuse antibiotics on ourselves.

We also put these drugs in animal feed and water to stop outbreaks of livestock disease before they have a chance to happen.

Those antibiotics can cause resistant bugs to evolve in animal populationsand then spread into crops or even into humans.

So when we use antibiotics, we are actually driving the evolution ofresistant bacteria, which is not a new problem.

Bacteria have always been evolving ways of resisting the things that tried to kill them.

And now, the overuse of antibiotics is exacerbating that problem.

In fact, Fleming himself was aware of the risk.

He said that when we overuse antibiotics, we are morally responsible for the deaths of those who succumbed to infections.

Now, I am not suggesting thatwe stop using antibiotics altogether.

We just need to get smarterabout when and how we use them.

For example, antibiotics are meant to treat bacterial diseases.

They are useless against viraldiseases like colds and flu, so using antibiotics to treat a cold is like using a hammer to fix a leak.

It won't work and it'llprobably make matters worse.

And this trend of killing anything bacterial goes way beyond just antibiotics.

We also put antibacterial chemicals in soaps and hand gels and toys, even socks.

And I don't think that's something that Alexander Fleming would have approved of.

To him, bacteria weren'tjust things to be destroyed.

Amazingly, he created this germ art using microbes as his medium.

Even though he discoveredthe most effective weapons against bad bacteria, he understood that bacteria could bebeautiful, sometimes helpful and certainly everywhere.