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  • - This episode is sponsored by Skillshare.

  • I saw these images circulating around the internet that

  • showed bacterial cultures growing in Petri dishes

  • and claiming to represent the effectiveness of masks

  • in stopping or minimizing the spread of germs.

  • It was in relation to COVID-19 and whether or not

  • we should all be wearing masks.

  • So today we're gonna recreate this experiment and

  • document it to see how accurate it was and whether or not

  • our mask results come out the same.

  • - Now we trace the images back to the Twitter user,

  • Dr. Rich Davis, love that very expensive name,

  • he is a director of a microbiology lab,

  • so yes, his results seem VV legit,

  • but we want to reproduce his demonstration on our own

  • for a few reasons.

  • One, because it's an excuse to do some fun at home science,

  • and maybe we'll have some new friends in quarantine,

  • aka these bacterial cultures.

  • Two we wanna see if our results will be consistent.

  • - Three, we really wanna test homemade masks

  • because the ones in the pictures look like surgical mask,

  • but I feel like a lot of people just made their own at home,

  • like these ones, my mom made that are super cool.

  • She just basically put two layers of cotton fabric together

  • and some elastics on them.

  • Mom, you did an amazing job,

  • I feel like a science superhero walking down the street.

  • So yeah, there's a whole bunch of them,

  • should she start a line?

  • Now, just before we start,

  • I know some of you might be screaming at your screen saying,

  • but Mitch Coronavirus is a virus, not a bacteria.

  • And that's totally true,

  • so let us explain why this experiment is still relevant.

  • - Right now scientists believe that the main mechanism

  • of transmission for SARS CoV-2 virus

  • is through respiratory droplets.

  • The virus doesn't just float around,

  • it relies on moisture from an infected person to trap.

  • And given that bacteria from the mouth, nose and throat

  • travel in the same way, while these dishes aren't gonna

  • show us how much SARS CoV-2 virus is on them,

  • it will show us the relative amount of droplets.

  • And these droplets by proxy are telling us how our germs

  • spread, whether we're wearing a mask or not wearing a mask.

  • - As an added bonus, I actually got some friends

  • who work in a lab at the University of Toronto,

  • who are also going to recreate this experiment

  • with us at the same time, but under even more ideal

  • conditions for the bacteria to grow,

  • which we'll get to in a bit.

  • Ultimately, all this is to test and figure out

  • how well masks work.

  • Okay, so we are here with our agar plates,

  • I've got gloves on, these have been sterilized,

  • we actually got them from our friend, Amanda

  • who works in a lab who was able to prep these

  • in a proper autoclave, and we've sterilized this countertop

  • and we're trying to be super careful because we only wanna

  • see what's actually coming out of my mouth.

  • - [Narrator] Hot. - Hot.

  • These are called LB plates.

  • Basically it means that the agar that's in them

  • is going to help the bacteria thrive.

  • There's other kinds that help fungus thrive,

  • but in this case, we wanna see the bacteria come up

  • cause that's mostly what's gonna come out of my mouth.

  • - [Narrator] Once we had all the plates ready to go,

  • we began the experiment.

  • We held each plate around 1.5 feet away from the face

  • and coughed twice on one, (coughs)

  • sneezed twice on one, (sneezes)

  • a fake sneeze had to suffice, talked for one minute to one.

  • - There's hydrogen and helium then lithium, beryllium.

  • - And sung for one minute to one.

  • There's hydrogen and helium then lithium, beryllium. ♪

  • - Finally, we then repeated all of these activities

  • with a mask on. (coughs then sneezes)

  • - This is the periodic table

  • The noble gas is stable

  • Now that we have all our samples done,

  • we're gonna keep them in this room

  • which is the warmest room in our house,

  • I'm literally like sweating right now.

  • All the bacteria, eats up all that agar goodness and grows,

  • and then we'll just come back and check on them soon.

  • - [Narrator] One week later.

  • - Now because we don't have an incubator in our home,

  • obviously, our samples will grow pretty slowly,

  • so I enlisted the help of some friends who work at the

  • Molecular Genetics Department at the University of Toronto

  • who are going to duplicate this experiment

  • under even more ideal conditions.

  • Of course, because of COVID-19,

  • we weren't allowed to go in the lab,

  • so they're gonna walk me through the important

  • differences right now.

  • - At the lab, we've used Brucella Blood Agar plates.

  • Brucella is a type of media and it's supplemented

  • with sheep's blood, heme and vitamin K,

  • and these are additional nutrients that a lot of organisms

  • in the microbiota need to grow.

  • - That won't necessarily change the result,

  • it will just help to amplify any of the bacteria

  • that are actually coming out of me, right?

  • - Absolutely, we would expect to see the exact same results

  • at home as in the lab,

  • except we might be seeing different species of bacteria

  • growing on our home plates than we are in lab,

  • and in the lab we're giving them a lot more nutrients

  • and a lot more conditions to help them grow even better.

  • - Also in the lab I know that or using an incubator,

  • why is an incubator useful and what does it actually do?

  • - So we typically grow bacteria in a 37-degree incubator,

  • and this is because our bodies hover around 37 degrees,

  • assuming you have no fever.

  • And so any microbe that grows inside the body

  • grow the best at 37 degrees.

  • - What do we actually expect to grow on these plates

  • and is any of it dangerous?

  • - In general what you're going to see is just

  • the commensal, normal everyday bacteria and fungi

  • that you have within us.

  • And we need them, they provide us our nutrients,

  • they help us digest our food,

  • they help protect us against other bacteria and fungi

  • that are trying to cause us harm.

  • Most of them are really helpful and also friendly.

  • - Yeah, they're our friends.

  • That's really cute, it's nice to know that.

  • - One other big thing to remember is that

  • we actually can't see viruses growing on plates in a lab

  • or even at home, and that's just because viruses

  • are so small.

  • So while this experiment is a great experiment at giving

  • a snapshot of what could be in your droplets,

  • this will not include any kinds of viruses and it's not

  • gonna include any types of bacteria or fungi

  • that can't grow in the conditions we provided them in.

  • So it's always gonna be an underestimation.

  • - This is the most important question,

  • what will you be singing to your Petri dishes?

  • - I thought long and hard about this,

  • and I've decided to go with the classic karaoke song,

  • Uptown Girls.

  • - Yes.

  • - [Narrator] Three days later.

  • - As if we ever would say it like that.

  • (both laughing)

  • - Alright, so we are ready to look at our results, we have..

  • - Say hello to our new little friends, to our roommates.

  • - Our plates have been growing for over a week,

  • maybe almost two now. - I think it's two weeks now.

  • - Whereas the laboratory plates are only gonna

  • have been two days.

  • All right, shall we start with coughing?

  • The Petri dish for coughing, there's no colonies on the mask

  • Petri dish and there's one big chunker chunker

  • on the no-mask Petri dish.

  • - And maybe another little one over there

  • but yeah. - Yeah,

  • with the lab results, we see no bacterial cultures

  • when coughing with a mask, and coughing without a mask,

  • we see one sort of smacked up in the middle,

  • really good aim.

  • Coughing, we weren't sick, we had a dry cough.

  • I remember while doing it being like,

  • is on anything coming out?

  • - So the sneezing Petri dishes are where we saw

  • the most difference.

  • So again, the masked sneeze showed nothing on Petri dish,

  • but the unmasked sneeze is out absolutely covered.

  • There's probably, I don't know, 50 little colonies growing?

  • - Hmm.

  • - Wow, I mean, obviously this is why,

  • even when there's not a global pandemic,

  • you sneeze into your arm.

  • Why when people sneeze on the subway you have a good reason

  • to be like, what?

  • - Cover your mouth.

  • And it's just so much.

  • I'm so surprised as that nothing seemingly made it through

  • on the masked one and yet so much made it through

  • without a mask.

  • The lab results were also interesting,

  • no cultures when you had a mask on with sneezing,

  • but then without the mask tons all over the plate.

  • - The plates from talking, we see without a mask,

  • there are about eight,

  • there's quite a few colonies growing,

  • with the mask, there are none.

  • So I think this is really striking because talking is

  • something that we are all doing.

  • Lab results show talking with the mask,

  • no bacterial cultures and talking without a mask, a lot.

  • - Yeah, I know it's actually surprising,

  • maybe almost as much as the sneezing in this case.

  • - This is why it's so important that you have a mask on.

  • - It probably depends how much enunciating we were doing.

  • - I was reading a study where they actually analyzed

  • using computers and like lasers, how many droplets

  • were coming out of people's mouths as they spoke,

  • and they got them to say stay healthy because the T-H noise

  • is known to create a lot of droplets.

  • I think the T-H noise yeah.

  • - So singing we're seeing nothing on the masked version,

  • and we're actually seeing quite a few drops on the no mask.

  • Do not sing without a mask right now people.

  • It's pretty, it's kind of staggering, there's probably

  • six to eight colonies starting, some of them big.

  • And this makes sense when you hear about how choirs

  • were spreading COVID and how they've shut down Broadway

  • for good reason.

  • - Finally, in the lab with singing nothing with the mask

  • and a lot without a mask.

  • So I'd be curious to see what would happen if this had

  • a full week like ours, it could

  • probably cover the whole plate.

  • So these plates are helping us to understand how much is

  • coming out of us and the effectiveness of masks in stopping

  • those droplets and not necessarily how effective the mask is

  • in protecting you.

  • So that's just something to take in mind.

  • - Yeah, wearing a mask is altruistic,

  • it's about you protecting other people around you,

  • which I think is kind of a beautiful thing.

  • I'm wearing this mask

  • for other people. - For other people.

  • And I also just wanna say that masks are potentially part

  • of the solution, but they're not the whole solution.

  • - Yeah. - So, we should be very masks,

  • we should be washing our hands,

  • - Physically distancing. - Yeah.

  • Isolating completely if you've ever been exposed.

  • And then obviously we're all hoping that vaccines

  • and treatments come together.

  • And that is kind of like a holistic look at how we can all

  • be working together to stop the spread of this virus.

  • Now, if you love learning and trying new things

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