A World Without Microbes: An Apocalyptic Thought Experiment | I Contain Multitudes

A World Without Microbes: An Apocalyptic Thought Experiment | I Contain Multitudes


[MUSIC PLAYING] ED YONG: Imagine wiping
out every microbe on Earth, every
bacteria, every germ. I’ve done that. That is Professor Jack Gilbert
from the University of Chicago. Catastrophic
ideas are exciting. Everyone loves a disaster movie. ED: This summer– JACK GILBERT: As a microbe
guy, you’ll like this movie. ED: In a world
without microbes– JACK: A world in which
all the bacteria, viruses, and unicellular fungi,
and anything which is only a single cell, right, or a
single particle, all of them are gone. One will– Wait. They’re all gone? JACK: We wanted to think
about the world in the absence of any microbial life. A world without
microbes means a world without microbial disease,
without the bacteria and the viruses and
the protozoa that infect us and make us sick. ED: An ideal world
for germaphobes. It would be an amazing
world for germaphobes. Right, because you wouldn’t
even need antibiotics. You could do surgery
in a barn and you wouldn’t get an infection. And in fact there would be no
sexually transmitted diseases. ED: No gonorrhea,
no syphilis, no HIV. Happy days. JACK: Very happy days. But we wouldn’t be able
to make any more beer. We wouldn’t be able
to make any more wine. They are virtually impossible to
synthesize without the presence of microbes. And microbes are really
important for digestion. They help us to break
down the food we eat, so whatever food we still had,
we’d have trouble digesting it. There are also some
bacteria in our gut that produce compounds,
chemicals, vitamins that we need, that we find
it hard to get from our diet. So without those
present, we would start to suffer from malnutrition. And the problems
don’t stop at digestion. JACK: Your microbiome
actually can affect your endocrine
system, that’s the hormones inside your body. And you always know that if your
hormones are out of balance, you feel kind of quirky, right? It can also regulate
the neurotransmitters that are produced in your
brain, which can affect things like depression and anxiety. ED: Wait, but that’s
just a hypothesis, right? You don’t actually have
any experimental evidence of how a germ-free person
would behave or feel. That experiment
is impossible to do. To grow a germ-free
human would be unethical. ED: Right, you’re not
raising germ-free humans in the basement of your lab. I wouldn’t be able
to tell you if I was. Yeah, maybe don’t reveal that. No, we’re not raising
germ-free humans. That would be weird. OK, so what you’re
saying is even the good things
about microbes won’t matter because our
bodies won’t even be able to function normally. And what about the
rest of the world? We’ve started to
head into horror-land. So essentially the foliage on
earth has started to brown. Most of the plants require
nutrients in the soil, which are generated by microbes. The crops would
start dying, so we’d have massive food shortages. The cattle, the sheep, which
rely on bacteria in their gut to break down all
that cellulose, the plant matter they
would be consuming, they wouldn’t be able
to get enough nutrients from their food. Most of the livestock
that we rely on would’ve started to
fall over and die. But it’s the lakes
and the rivers and the oceans where we would
see the worst horror stories. ED: Right, just as
on land, microbes are a crucial part of
our lakes and rivers. They cycle nutrients, they
maintain animal health. So without them– JACK: You’d have mass
die-outs of fish, and they would be all
floating on the surface. ED: You are way too
happy right now. Yeah, right? It’s a great thought experiment. Nasty, but I love zombie
movies and disaster movies. I think we naturally
want to see what would happen if all of this
normalcy decayed, right? And speaking of decay, in
a world without microbes– JACK: The decomposition
process would be halted. There’d be no more decay. Within a few years, if
we survived that long, we’d be knee deep in animal
corpses and leaf litter. So the world would just
become a graveyard. Once all the animal
corpses had been eaten, and we don’t have any
animals in the city to eat, right, then people would
start on cannibalism. Cannibalism? It’s highly
likely people would resort to eating whatever
products they could get. And, likely, because the
bodies wouldn’t be poisonous, right, there’d be no pathogenic
bacteria growing in them. It’s a normal societal
endpoint for starvation. Wait, microbes produce a
lot of oxygen too, don’t they? A lot of the
oxygen is produced by single cellular bacteria
or the organisms that live in the ocean. ED: So if all of those vanished,
there would be much less oxygen for us to breathe. JACK: No one’s done
a biological survey on what would happen if
the oxygen level plummeted. ED: I miss my microbes. I miss them, too. In fact, the whole world
is missing them right now. So, what happens to
me and you and the seven billion other people
on this planet when the microbes all disappear? We’re talking about
people suffocating and not able to consume enough food. The world is dying. It’s not like just humans
are killing each other, but the world is dying and
the oxygen is running out. It’s global death, right? ED: And this particular
horror movie has no sequel. JACK: There’s no sequel. This is game over. Microbes are important. JACK: Without
them, we’re doomed. Literally. So rejoice in your microbes,
the trillions of tiny organisms that call you home. Treat them with respect, and
they will return the favor. We are Ed, and we
contain multitudes. If you liked today’s
thought experiment you can join Jack Gilbert
for a Reddit AMA coming soon. Jack will be joined by Mark Smith
from our episode on Fecal Transplants and together, they will be answering
a slew of your microbial questions. Check out the description
for more details.

13 thoughts on “A World Without Microbes: An Apocalyptic Thought Experiment | I Contain Multitudes

  1. Man, this really does need a Hollywood treatment. It’s amazing how much we rely on the smallest organisms around us to survive.

  2. This is about what would happen in the earth's biosphere today. Leaves out the real story of A World Without Microbes for 4.5 billion years. That would be a short story about a world that never had anything living on it.

  3. Well, the mass die-off of fish wouldn't result in fish floating on top of the water. The floating occurs because of bacteria decaying the fish's flesh produces gasses that make the corpse float. See, the apocalypse will be much more photogenic than that! : – )

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