- [Narrator] Centralia, Pennsylvania is a ghost town.
Nearly 3,000 people used to live here,
but these days it's almost completely abandoned.
And it's pretty eerie, but that's okay
because what we're looking for
is actually in the soil.
Some 100 meters below us
an underground fire is burning away.
It's what turned Centralia into a ghost town.
But while almost all of the people have fled,
some tiny microbes have appeared.
Among them, thermophiles, critters that live
at super hot temperatures.
We're hoping to collect some thermophiles
and grow them in our studio.
We'll look at what happens to life in extreme environments.
- I think we should take a sample here.
- [Narrator] And we'll get a glimpse
into what microbes might be hiding in soil
all over the world, waiting patiently
for a calamity to call their own.
- Oh yeah, you can actually feel...
there's a little bit of steam.
I don't think the cameras can pick it up.
- [Narrator] Our mission today is to collect
a couple types of microbes from the soil:
bacteria and archaea.
We're working in the footsteps of a researcher
from Michigan State University named Ashley Shade.
She's the principal investigator on a recent paper
that looks at microbes here in Centralia.
It's an effort to understand what happens
to microbial communities when, for example,
the ground itself catches fire and burns for decades.
- And so the big premise, the big question
was about how did those systems respond
and are they capable of recovering
from such a sledgehammer of a disturbance?
- [Narrator] The story of what happened here
is dramatic.
Centralia was a mining town,
but the coal mine that supported it
was largely exhausted by the 1960s.
The fire actually had nothing to do with mining.
In the summer of 1962, some burning garbage
at a nearby landfill ignited the coal seam
that remained under the area.
This set off a massive subterranean blaze
that proved extremely difficult to contain.
The fire encroached on the town year over year,
venting dangerous gas into the air,
and ripping fissures in the local highway.
- I think now you can tell why they closed the highway down.
- [Narrator] People began to flee in earnest in the 1980s,
and today, the government has relocated
almost all its residents.
What happened in Centralia was disastrous,
but it also set in motion the science
we're here for today.
- The vegetation has changed.
It doesn't look like it's that much different,
but you can feel the ground,
it's much softer than it was on the other side of the road.
- [Narrator] Once we were all set up,
we sterilized our tools and got to work.
Finding active fire areas is tricky
because again, the fires are underground,
so we basically looked for hot soil.
- Unfortunately, there's no steam
'cause it's not cold enough outside,
but this would be a good candidate for a place,
I think, to take a soil sample.
- [Narrator] We hiked around a little.
- I want to go take some readings in here.
- [Narrator] We hitched a ride to a sinkhole
from a guy in an off-road vehicle,
and we generally combed over the area from Ashley's study.
- So we're at the St. Ignatius cemetery now.
A lot of the papers that we read
talked about the "turquoise zone,"
which is the ridge just north of the cemetery,
and that's where they found a lot of the hottest readings,
so we're going to go take a couple samples from that zone
and see what we can find.
- [Narrator] But site after site,
and reading after reading, we didn't find much.
- It's kind of cool right now,
but I think we should take a sample.
This ain't it.
Alright, I'm getting colder over here.
Maybe the fire is finally gone after all these years.
(laughs) I don't think that's the case.
- [Narrator] We were hoping for soil
that was maybe 40 or 50 degrees Celsius,
but we kept finding 15 to 20.
It was barely warmer than the air,
so we called Ashley's research assistant Keara
for help in real time.
- [Keara] What I was kind of hoping maybe...
would be to just get into video chat and have you look around
or something.
What might work is if you just kind of be the eyes
and I can walk you to some places.
It's all just stuff that lives in my brain.
- You're on camera.
- [Keara] Oh hello, hi!
- It's an adventure.
- [Narrator] Keara led us to a couple new spots.
- [Keara] Somewhere up ahead and to the right.
- [Narrator] We dug a little deeper,
and finally found some promising soil.
- Now I'm getting a reading of about 27 degrees Celsius.
That goes pretty deep in there, too.
- [Narrator] Now 27 degrees Celsius might be low
for finding thermophiles,
there are plenty who thrive in places twice as hot,
but it was abnormally warm for Pennsylvania soil in March,
so we grabbed some samples, put them on ice
to keep the microbes at rest,
and headed home to grow them.
- So the first step to regrowing our microbes
is getting them out of the soil,
and that part's pretty easy.
We just mash up the clumps, add some distilled water
to create slurry, and shake everything up.
- [Narrator] Once the slurry settles, there should be
plenty of microbes floating around in the water.
This part's trickier.
We dilute the sample by different amounts,
and grow a petri dish full of microbes using each dilution.
The idea is to grow enough microbes to study,
but not so many that they'll take over the petri dish.
With our samples prepped,
we spread a bit of liquid from each dilution
onto a petri dish filled with nutrient-rich gel.
We're growing microbes from a couple hot soil areas
and also from a place that was
never exposed to Centralia's heat.
That's our control group.
- Ashley and Keara did grow some microbes of their own
just like we're doing, but it gives them
a pretty incomplete picture of what's there.
- So that's because we can't culture
99 percent of the bacteria and archaea that are found in soil
just because we don't know how to,
we're unable to bring them into the lab.
- [Narrator] It's a mystery that
lots of scientists puzzle over.
Many microbes just refuse to grow in a lab environment.
So Ashley's team resorts to higher tech methods.
- What we do is we extract all of the DNA from the soil,
and then we sequence it.
And we use that sequencing information
to put together whole genomes of organisms
that lived in that soil.
- By sorting through all the DNA present,
they can look for trends in the samples.
Ashley's team collected samples
from a range of temperature areas in Centralia.
Places that were hot, others that cooled back down,
and others still that were
never affected by the fire.
That way they could sniff out correlations between things
like temperature and genome size.
- [Narrator] Our final step is to pop all of these samples
into our incubator.
We're going to grow them at around 55 degrees Celsius
for two to three days.
Some samples might take longer.
After three days, we checked our little microbe oven.
- Oh, so gross, oh.
- [Narrator] And we got to work filming the samples
so we could ask Ashley and Keara what we found.
Again, this isn't quite how Ashley did it.
Once her team sorted through their DNA,
they checked it against available DNA libraries,
and a surprising amount of the DNA they found
is a mystery.
- I'd say about 30 percent of what we find is unclassified.
We know that they're bacteria or archaea,
but we don't know anything else other than that.
- [Narrator] For the record, bacteria and archaea
are domains of life, which is basically
the broadest category.
- And so that's like basically saying
"I've identified this organism,
but I don't know enough about it
to tell whether or not it's a jellyfish,
a human, or a tree."
- That said, they are learning a ton from their collections.
One big takeaway is that the thermophiles they found
tended toward smaller genome sizes
and smaller cell sizes.
It's not totally clear why,
but one popular theory is that it's just
easier to maintain smaller hardware at higher temperatures.
- And so the idea is if you can keep your cells small,
you are going to benefit by not having to
spend so much energy just maintaining
all of your cell parts, which are kind of
getting more wobbly at the higher temperatures.
- So what exactly did we find?
Well first, our hot samples grew a lot more
than our cold control group did,
and there's a logic to that.
We regrew all the samples at a pretty high temperature
and the microbes that seemed happiest with that
came from the hot soil.
But overall, eyeballing microbial life is tough.
Keara was pretty confident that these structures here
are bacteria, but it's hard to say much more than that.
This is exactly why DNA sequencing
is where most of the science happens.
There may well be thermophiles
growing in these petri dishes,
but we'll need a lot more tech to point them out.
After this whole process, our biggest question
was "Okay, Centralia caught fire
and a bunch of microbes appeared to capitalize on that,
but where on earth did they come from?"
There wasn't nearly enough time for the microbes here
to evolve a heat tolerance, so what's going on?
- This is a question that a lot of people
are curious about because you can find thermophiles
in the coldest, weirdest places on the planet Earth.
You can find them in the permafrost, right?
You can find them in the deep ocean cold sediments,
you can pull out some thermophile spores
and resuscitate them at hot temperatures.
- Ashley's guess is that these microbes
have been in Pennsylvania, dormant for a long time.
Where they originally came from and when
is a total mystery, but it suggests that wherever you look,
there might be dormant life
that thrives in extreme temperatures.
And as the planet warms,
these questions become more pertinent.
Even a couple degrees could change the dynamic
within microbial communities all over the world.
That might not be disastrous,
but it's worth understanding.
If every community has its optimum temperature,
we could see spikes all over in microbes
that are doing the same thing
the thermophiles in Centralia did:
lying dormant and waiting.
- That's a good way of talking about it.
They are definitely playing the long game.
- We should make an executive decision
if I'm using Fahrenheit or Celsius.
I'm all over the place.
I'll keep this on Celsius.
I just... when I see 24, it's going to be a (bleep)ing
disaster to edit. (laughs)