Like Elise, I'm an engineer and I also use biology to be able to answer questions
and solve problems. And I'm specifically going to be focusing on microbes
or the little tiny living things that are found pretty much everywhere.
Elise introduced one type of microbe and that's HIV, which is a type of virus
but there's lots of other types of viruses including the flu, which can make us sick
and another type of microbe that you might be familiar with is mold, or fungi.
And this is a microscopy picture of some mold, actually the mold that you might
find on bread. And this is called Penicillium. And you might recognize
that name, because this is a type of mold that we use, that is now used to make
an antibiotic. Other types of mold and fungi you can actually find on your skin.
And these are really important for the health of your skin
and having bad bacteria not infect you. Bacteria are another type of microbes.
Here I have an image of an E. coli cell. Many of you might be familiar with E. coli
because frequently there's times when we can't eat lettuce or other leafy greens
because of E. coli infections making people sick and causing them to throw up.
However, we also have E. coli that's not harmful in our stomachs and in our guts
that help us actually digest food. So this shows how bacteria, even though we often
think of them as germs and bad, can also be good.
Another type of microbe that I want to talk about is protists. And if you've ever looked
at pond water under a microscope, then you might have seen amoebas,
and that's what you can see in this picture. And this is just one type of protist.
When we look at all these different types of microbes together for a particular
environment, then we are looking at the microbiome. And if you've heard of the
human microbiome, then you might have heard of these other bacteria and fungi
and viruses that also make up our own, are in our bodies.
And so, to introduce the idea of some other microbiomes, and some that
environmental engineers might care about, I want to quickly show a clip from a video,
so I'm gonna switch to that. ♪ (Intro music) ♪
(applause)
Humans in the developed world spend more than 90% of their lives indoors,
where they breathe in and come into contact with trillions of life forms
invisible to the naked eye, micro-organisms.
Buildings are complex ecosystems that are an important source of microbes that are
good for us and some that are bad for us. What determines the types and distributions
of microbes indoors? Buildings are colonized by airborne microbes that enter through
windows and through mechanical ventilation systems and they are brought inside
by humans and other creatures. The fate of microbes indoors depends on
complex interactions with humans and with the human-built environment. And today,
architects and biologists are working together to explore smart building design
that will create healthy buildings for us.
And so, for my research, I'm really interested in understanding, what are
the differences between microbiomes that make us sick in buildings and then
ones that don't. One thing that you might have noticed while watching this video
is that, even though you couldn't see people in it, you could see the traces of the
microbes that we leave behind. And this is often very relevant to the spread of diseases.
However, it also leads to many microbes being in the air, and so for my reserach
I want to have a way to see what microbes are we actually being exposed to.
And, the way that I do this, is very unexciting, but it's actually using dust.
And in particular, it's using dust that you might find on the surface of door frames.
And if you look at this dust under a microscope, then what you'll see is,
you can see like fibers from like your clothing or carpet,
but you'll also see things like fungi.
But, by just looking at it under a microscope, you don't get as much
information as we need to be able to tell the difference between healthy homes and
homes that make people sick. And so, what I'm able to do is, like Elise said earlier,
in the nucleus, then you can see, that there is the genetic material. And that DNA,
we can actually sequence. And by sequencing it, it's like Elise said, that's the book
or the instructions, for making a cell, and by comparing between different micro,
between the microbes that are found in one building, to another, based on their DNA,
then you can actually look at who's there. And so with my research, I'm actually
finding kind of a fingerprint for the microbes that are present in dust.
However, another microbiome that we care about in people's homes is actually that
of tap water. And most of the time we don't think of there being living things in
our tap water and that's because environmental engineers are really good
at filtering tap water to remove bacteria and viruses
and other things that can make you sick.
However, sometimes, there is bacteria that can actually grow within our pipes
and that growth can lead to people who's immune systems are compromised to getting sick
And so, for this other project that I'm going to be talking about,
what I'm looking at understanding is, by understanding the bacteria and the viruses
that infect the bacteria, can we design better drinking water treatment processes?
Typically, when we think of viruses, we think of the virus's that infect us,
infect human cells, so things like HIV or COVID. However, many viruses,
most viruses, actually infect bacteria, and so, in this diagram you can see hexagons,
which represent viruses, and then blue circles that represent bacteria.
And what I'm trying to understand is, which bacteria, which viruses,
go into which bacterial cells. And the way that I'm doing that is by filtering
lots of water. And then what I can do is look at it under a microscope.
For instance, this is a picture taken with a microscope where you can see these
little rods, which are bacteria, and some little spots, that might not show up too
well on Zoom, but you'll have to take my word for it if you can't see them,
that are actually viruses. But, if you look at this picture, you can see that
there's not a ton of information, and so that's why, again, I want to use
DNA sequencing to get a fingerprint, or to understand which viruses and
bacteria are actually there. And just like our fingerprints are unique to us, our DNA
is also unique to us. And so, by comparing these DNA sequences we can figure out
which bacteria and which viruses are present. And hopefully,
through this understanding, I'll be able to design treatment processes that are
better able to ensure that everyone has safe drinking water.
So with that, I'd be happy to take a few minutes of questions.
[Emily] Alright, so thank you Bridget. So, to get started, some people were curious
how the same microbe can both help us and make us sick.
[Bridget] That's a great question. And it's because how you classify microbes
is very important. So, I was talking about E. coli, and that's a species of bacteria.
But, within a species, you have what we scientist call strains of an organism.
And so, the differences, very small differences between different strains of
E. coli can actually mean that some infect us and some don't make us sick.
And part of the reason that this is so important, is that bacteria are able to
evolve, or change, their DNA really quickly, and so that means that a bacteria that was
previously harmful can become harmless, or, on the other hand, one that wasn't
harmful, that didn't cause harm can then cause you to get sick.
So, excellent question, thank you.
[Emily] Great. And then the next one is what makes some microbes harmful to humans
and not others?
[Bridget] That is another excellent question. So this is a really big question
and to answer it properly would take me a long time. But, to answer a few reasons is
typically the reason a particular microbe makes us sick is because it causes
our immune system to have a response. And that's because our immune system is able
to recognize things that are part of us, as self, and things that are foreign as
shouldn't belong there. And so, most, some bacteria are then recognized as foreign
And so, if they're recognized as foreign, then our immune system wants to get rid
of them, and that leads us to have like a runny nose or a cough. And so, that's
what's happening with a lot of bacterial, fungal infections, viral infections.
And with viruses, and with bacteria, it's really important that our immune system
is able to recognize some of these bacteria as bad for us because,
for instance as Elise said, a virus can take over the machinery of a host cell,
and then make more. And so, if the immune system wasn't able to find these harmful
microbes, then they would continue to divide and eventually take over our entire
bodies, and so that could lead us to die. The microbes that don't make us sick
typically they survive at levels such that they are not harmful and they actually do
processes that help us, for instance, helping us to digest food.
[Emily] Great. And then, another question, will the type of microbe in tap water
depend on the location?
[Bridget] That's another great question. And yes, it will. And one of the projects
I'm on right now is looking at tap water from across the world and seeing what
differences there are between tap water say from Europe or from China or from
the United States and by finding those differences we can actually learn
information about how different forms of drinking water treatment work and
which microbes get through certain drinking water treatment processes
Because different towns treat drinking water in slightly different ways and
different countries also do the same thing. And so it's really interested to
be able to understand the effect that treatment process has on which microbes
are there. Also, the microbes in a particular environment are different.
So even if you had the same treatment process in two very different climates
then you are also going to see different micro-organisms. Similar to how the plants
outside might be different if you're in Europe versus somewhere in the US.
[Emily] Great. And then, someone was curious: who takes samples for your
world-wide project?
[Bridget] So, for the world-wide project, it's actually a lot of different research
groups. And one of the really cool things about science is that once you've done
your experiments and you've published about it, then you'll share your data.
And so, because other scientist have shared their data, then we can actually
take their data and learn about it. So it will be research groups in those
different countries.