[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… 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.
