[FLOWING WATER AND ELECTRONIC MUSIC]
[SOUND OF WATER DROPLET]
[MICROSCOPE SLIDE CLICKS INTO PLACE]
>>SALLY WARRING: We are surrounded by hidden microscopic worlds filled with fascinating
life forms.
Thousands of microbial organisms live within a single drop of water.
On Pondlife, we’re going on a safari to explore the microbial wildernesses that exist all
around us.
Today I’m out looking for a group of organisms that evolved over two billion years ago.
These organisms were the first to live by photosynthesis.
That’s the process of using sunlight to make sugars and then those sugars are used
to power the cell.
A byproduct of photosynthesis is oxygen, and two billion years ago these organisms became
so abundant that they completely changed the Earth’s atmosphere.
It went from one that was very oxygen poor, to the oxygen-rich atmosphere that we live
in today.
These microbes are called cyanobacteria and lucky for me, they are just as abundant today
as they were two billion years ago.
In fact, I haven’t had to go very far at all to find them.
I’ve simply walked out the door, I’ve crossed the road, and I can already see a
pond that is teeming with cyanobacteria.
[BUBBLING ELECTRONIC MUSIC]
>>WARRING: You can find cyanobacteria all over the world.
There are currently around 3,000 described species with different morphologies and habitats
from freshwater ponds to arctic oceans.
They even live in soil.
As I wander around Central Park, I’m on the lookout for signs of cyanobacteria.
[LILTLING ELECTRONIC MUSIC]
>>WARRING: It’s cyanobacteria that are making this pond so green.
If you look closely at this water sample, you can see that it's full of tiny, floating, green
particles.
Each one of those particles is a colony of cyanobacteria and each one of those colonies
is made up of multiple individual cyanobacterial cells living together.
To find out what species of cyanobacteria is living here I’m going to have to put
it under the microscope.
The cyanobacterium blooming in the Lake belongs to the genus Microcystis.
Microcystis colonies are made up of many individual cells suspended in a clear mucus.
A colony may start as one cell…
which divides to become two cells...
then four…
and so on until some colonies are large enough to see with the naked eye.
[POPPING ELECTRONIC SOUNDS]
>>WARRING: The colonies grow fast in warm summer waters,
and when their numbers get dense enough, we call this a bloom.
Many cyanobacterial species are bloom-forming, and you can distinguish each species by their
unique colony shapes.
One advantage of living as a colony is that when many individuals live together, tasks
can be divided among the members.
We can see this in another cyanobacterium from the lake.
This one belongs to the genus Dolichospermum, and among its helical colony, some cells look
a little different from the rest.
These specialized cells are called heterocysts and they have given up their photosynthetic
ability to focus on the task of absorbing nitrogen.
They build that nitrogen into molecules that can be shared and used by all the cells in
the colony, and in return the other cells share the sugars gain through photosynthesis
with the heterocyst.
By dividing up these tasks, each is run more efficiently, and the colony can prosper.
[UPBEAT ELECTRONIC MUSIC]
>>WARRING: Thousands of visitors walk through Central Park every day, mostly unaware of the many
tiny dramas playing out all around them.
With a microscope, we can catch a glimpse into these unseen worlds.
The bloom in the next pond is dominated by a cyanobacterium from the genus Aphanizomenon.
Aphanizomenon forms long, thin, filamentous colonies.
And while at first they appear to only drift, under time lapse we can see just how busy they are.
[RUSTLING ELECTRONIC SOUNDS]
>>WARRING: There is a good reason to stay on the move.
Cyanobacteria sit at the base of the food chain and are good eating for a number of
small predators.
This ciliate is a specialist cyanobacteria predator.
It’s from the genus Nassula and it's using its sensitive cilia to feel out a filament,
searching for an end.
Once located, it begins its work, sucking in the cyanobacteria like a strand of spaghetti.
[WHIRRING ELECTRONIC SOUND]
>>WARRING: As the cyanobacteria get ingested, the filament bends and breaks,
allowing it to fit inside the rotund little ciliate.
[WHIRRING, SLURPING ELECTRONIC SOUNDS]
>>WARRING: This process can take a little time, especially if the filament is particularly long.
The ciliate keeps going…
and going…
and going...
until the cyanobacteria are completely swallowed up.
Delicious.
[BUBBLY ELECTRONIC MUSIC]
>>WARRING: When I’m out looking at these microbial communities, I often see things that I want
to take a closer look at.
And there’s only so much I can do out in the field with my portable microscope.
So, when I see something interesting, I take a sample and that comes with me back to the
Museum and into the lab.
[BUBBLY ELECTRONIC MUSIC]
>>WARRING: While I’m working with the pond water, I want to keep everything sterile.
This is because I don’t want microbes that might be growing in the lab or on me to end
up growing in my lab cultures.
Now that the microbes are out of the pond and in the lab, I also need to make sure they
have everything they need to survive.
The bottles here contain different types of growth media. Each medium contains vitamins,
minerals, and salts that microbes need.
This big thing is a biosafety cabinet and it’s going to help me keep everything sterile.
I wiped everything down with ethanol before it went into the cabinet, but it also has
this wall of air that passes from this vent at the bottom right up the front and that
prevents any microbial spores that might be in the air from travelling though into this cabinet.
At the same time, the cabinet is constantly sucking air up through a vent in the top and
that means that if any microbial spores do make it through into the cabinet, they get
sucked up into that vent rather than landing on my cultures.
I add a small amount of pond water to liquid medium or spread some out onto an agar plate.
That agar plate contains growth medium too, but it’s been solidified by the addition
of agar—a kind of jelly-like substance that’s produced by certain seaweeds.
Some microbes prefer to grow on the solid surface of the agar, while others grow better
suspended in the liquid medium.
I keep those cultures in a growth chamber, the growth chamber maintains the temperature
and provides a constant amount of light each day.
Cyanobacterial blooms can cause real problems, some produce toxins that are lethal to many animals.
I’m interested in the microbes that thrive here, organisms like these flagellates, and
this euglena algae,
or this collodictyon, all living among the bloom.
Over the next few weeks some of these microbes will grow in numbers, until eventually
I can isolate and identify individual species from those liquid cultures,
and from the agar plate.
I’m hoping that by growing and studying some of these microbes that are present in
the cyanobacterial blooms that we’ll learn more about the blooms as communities, and that
we can understand some of the things that are causing these extremely common phenomena.
Even our biggest cities contain microbial ecosystems that are vibrant and complex.
Growing these organisms in the lab helps me to understand just what thrives
in this microscopic metropolis.