- [Narrator] Think of cheese.
What pops into your mind?
Creamy, tangy brie?
Dry, crumbled feta?
This thing that smells like gym socks?
There are countless varieties,
but they all basically share the same building blocks,
some milk, some salt, and some rennet.
That's just enzymes that help the milk curdle.
And then there's a wild card,
a whole lot of microbes that scientists and cheese makers
are still trying to catalog and understand.
Take this cheddar, for instance.
It's called Stockinghall Cheddar
and it's made by Murray's Cheese in New York City.
Scientists at Rockefeller University
have been studying what communities of microbes
live on this cheddar as it ages.
Cheese is a complex ecosystem.
As it matures, entire populations of bacteria, yeast, and
mold rise and fall.
These microbial changes play a big role
in how different cheeses develop different flavors.
And today, we finally have the tools
to study the changes up close.
Microbiologists Jeanne Garbarino
and Odaelys Walwyn at Rockefeller University
have been collecting samples
of the Stockinghall Cheddar for over a year.
Their microbe experiments are part of an outreach program
with high school students.
- You eat cheese all the time.
Do you ever think of cheese is actually made up of microbes?
Wouldn't it be cool to try to figure out
what microbes they are?
- [Narrator] They may also have less educational motivations
when it comes to the cheddar.
- Basically, you had to take it away from me
'cause I would have eaten the whole thing.
- [Narrator] Every week, Jeanne and Odaelys
went to Murray's cheese caves in Queens,
where the cheddar is aged.
They swabbed the rinds as well as the shelves
where the cheeses are kept,
and they took samples of the inside of the cheese.
And about a year ago, I tagged along.
- [Man] You need a hair net, you need a beard net.
- [Cameraman] Cool.
(laughing)
- Oh, my god.
- [Narrator] Over the past few years,
Jeanne and Odaelys have identified the microorganisms
living on the walls, shelves, and
floors of the cheese caves.
So, by the time I arrived, they already had some idea
of what usual suspects they'd find on the cheddar.
- [Odaelys] So definitely expecting some lactobacillus,
lactococcus, probably some mold, maybe some candida species.
Some yeast, maybe some streptococcus.
- [Narrator] Lactobacillus and lactococcus
are the most obvious and crucial.
They turn the milk sugar into lactic acid,
kick starting the fermentation process.
As time passes, different organisms break down
milk fats and proteins to get energy.
That transforms the cheese and adds flavors.
The next step is to bring the samples back to the lab
and sequence their DNA.
That allows us to ID the types of bacteria and fungi
that are found in the cheddar at different points in time.
This is called microbial succession.
And cheese is an ideal place to study it.
Picture succession like the evolution of a forest.
- [Jeanne] We can think about like a really rocky terrain.
And as rain and other types of weather patterns start
eroding the rock, they might put some little cracks
in the rock, maybe you have some lichen start popping
on the rock, or some mosses start growing on top of that.
And then eventually maybe you get a little bit of grass and
then maybe you get some shrubs and then maybe you get some
trees and then all of a sudden, you have a forest.
- [Narrator] As cheese ages, communities of microbes
change in a similar way.
Just like climate change alters big ecosystems,
cheese makers can change the temperature and
humidity of their caves.
That will alter the moisture and acidity of the cheese,
which will change the microbe profile,
which in turn changes the flavor.
- As time progress, you 'll see that one microbe
survives for about a month or two and then another one
comes along, and say hey, you know, this is actually
my spot and this environment is better for me
to survive in than the other person.
- [Narrator] Microbial succession actually happens
in any fermented food.
Like wine, pickles or yogurt.
Humans have been fermenting foods for thousands of years.
Ancient Egyptians made cheese and yogurt.
The Greeks and Romans drank plenty of wine.
And in ancient China, people fermented veggies.
But it wasn't until the 1800's that we got a better idea
of what was really going on.
And it all started in France with some beet juice.
- This guy was, Monsieur Bigo was basically
trying to ferment this beet juice so that they can create,
so they basically can create some beverage that
people can get drunk off of.
- [Narrator] But as the beet juice was aging,
Bigo hit a snag.
- And then all of a sudden, it was souring, right?
And so people could not get drunk off the stuff
cuz it was, something was happening.
- [Narrator] So they decide to bring in an expert,
renown chemist Louis Pasteur.
Pasteur looks at the beet juice under a microscope and
sees something weird.
There was one set of organisms swimming
around the sour juice and a different set
in the boozy juice.
- And so it was much different.
So he then identified that microbes are potentially
the source of the fermentation process and specific microbes
are important to achieve different results.
- [Narrator] So what does all our fancy
DNA sequencing reveal about the Stockinghall cheddar?
I had to wait a while to find out.
A year after it went to the cheese caves, Jeanne and Odaelys
had some preliminary results to share.
At around month four or five, the bacteria
on the Stockinghall rind began shifting.
From lots of lactobacillus and lactococcus
to more brevibacterium and brachybacterium.
The first is known for giving some cheese
that funky foot odor smell.
But the other, we don't really know why it's here or
what it's doing to the cheese.
All of this is more of a curiosity.
And a small drop in the big bucket of cheese research.
But just knowing how bacteria interact on cheese
gives cheesemakers like Murray's key intelligence
on how their products are made.
And it tells us a whole lot about the universe
of microbes living all around us.
- Before we had access to the technology that we have now,
we had no idea what was going on in the microbial world.
We could only culture less than one percent
in a laboratory setting.
And so now, what we're doing is we're able to get a more
authentic snapshot of how microbes are growing
in certain conditions and again, I think cheese is just
one of the most beautiful ecosystems to study.
- Hey everyone, thanks so much for watching.
Please make sure you subscribe to our new Verge science
Youtube channel.
And check back every week for a new video.
And if you're into food science, let us know
what you want us to look into next.
Hopefully it won't take a year.
Thank you.