2022-10-15 by Khushi Goel

[Transcript] IndiaAsksWhy | Why Do We Brush Our Teeth?

[00:10] Both- “Hi Everyone”

U- I am Utsuka

J- I am Jigyasa

Both- And you are listening to IndiaAsksWhy.

U- A science podcast supported by IndiaBioScience

J: Where we do the research for you to get smarter.

U: Join us, as India becomes more curious,

Both: one question at a time!

[0:33] U: Utsuka and Jigyasa were chatting about the day when they had loads and loads of chocolates. And while having chocolate learnt about why we all love chocolate so much. That’s when Jigyasa came up with yet another curious question, “Why do we brush our teeth''? Listen to the episode to learn about microbes on our teeth and what causes cavities. They also talk with Dr Karishma Kaushik, a physician turned scientist to discuss how researchers study different microbes of the mouth in the lab.

[01:18] U: In our first episode, we enjoyed eating chocolate. Oops! I meant we enjoyed discussing why we like chocolate.

[01:28] J: When I was young, mom used to say if I ate a lot of chocolate, I would get cavities.

[01:38] U: Haha! Your mom is right, Jigyasa. That’s why we remove chocolate or food stuck in our teeth by brushing.

[01:44] J: Yeah! But Utsuka, why do we need to brush our teeth to remove the food, can’t I just gargle? Also, how does chocolate and food cause cavities?

[Typing sound]

[02:01] U: Hmm...To answer your question, we first need to understand our teeth better.

J: What do I not know about them? We have different types of teeth; all have an outer coating made of enamel -- the hardest substance in our entire body. U: Yeah yeah, that's all cool. But let's focus on something else. Something that we can’t see. There are 700 different kinds of microbes in your mouth and a large proportion of them live on our teeth surfaces in what’s called ‘biofilms’.

[02:35] J: Wow, but eww...

U: Hey, they are not eww! Just wow. Microbial communities, the biofilms, are essential. They keep our immune system and germs in check. In other words, the microbes in biofilms are in symbiosis with each other and with us – humans.

J: Oh! So, wait…what’s biofilm?

[03:03] U: So, microbes don’t live alone, isolated on our teeth. Diverse microbes that first come to live on your teeth produce a common film or matrix which acts as a safe place for all of them to thrive and communicate. Later, many other microbes go and live in them, too. Not all microbes come of course. Only the ones like the teeth environment reside there.

J: And you said they were in symbiosis with each other, right? [03:42] U: Yes. Microbes in biofilms live in harmony. For example, one kind of microbe takes up the food we eat, digests some bits of it, and passes on the rest for others in the matrix or film to use. They also share information about new food, microbes which may be stealing food, and so on. All this is possible because they have a common platform to communicate, the matrix. J: How does the matrix help?

[04:15] U: Let me give you a comparison. Isn’t it easier to share pens among each other if you are in the same classroom than to share them with someone who is in a different classroom.

J: Makes sense. But what does all this have to do with chocolates and cavities?

[04:36] U: So, microbes in biofilms are living peacefully, sharing, and caring. But when there's chocolate stuck to your teeth, something happens...

J: What happens?

U: See, chocolate mainly consists of…

J: Sugar! [04:53] U: Right. So the microbes in biofilm digest the sugar, convert it into acids and release those acids to the matrix. And sensing the acid comes microbes of biofilm that love delicious acids.

J: Acids are not delicious... [05:13] U: They are to these acid-loving microbes. After digesting acids, they produce more acid, in turn attracting more acid-loving microbes. Acid-loving microbes are now in majority in these biofilms instead of sharing and caring microbes.

J: So, the acid-loving microbes took over... that's a problem? [05:41] U: They convert more of the sugar into acids and change the environment. That means the microbes that usually live in the teeth biofilm become the minority. That destroys the peace. The not-so-peaceful biofilm is that sticky substance on your teeth – dental plaque. AND importantly, the acids the dental plaque produces slowly start to make a hole in your tooth's enamel.

J: Hole into the hardest substance?

[06:19] U: That's how powerful the acid these microbes produce!

J: So, that's how the cavity is created. Now I get why you bought biofilms into the conversation. This is fascinating and scary at the same time. It’s like a tug-of-war is happening in my mouth all the time.

[06:40] U: Aha, a microbial one…

J: Wait... this means that there are no external germs causing cavities? Cavities are caused by an imbalance of microbes in the biofilm? And that imbalance happens when the sugar from chocolate or other carbs gets stuck in my teeth?

[07:04] U: Yes, you grasp things so well! There is no one culprit germ here!

J: So, brushing removes food to ensure the balance of microbes in the biofilm, right?

U: Yes, brushing teeth ensures we don't let sugars ruin the balance. But it also disrupts the matrix so that when the biofilm forms back, only the regulars come back.

J: Wow. I will brush my teeth twice a day!

[07:41] J: Going back, you said there were 700 species of bacteria in biofilms just in our mouth? How did scientists study them?

U: Yes, let's learn more about biofilms from Dr. Kaushik, shall we?

[07:57] J: And now, it’s time to ask a scientist.

[08:01] J: Welcome back! And now we have with us Dr Karishma Kaushik. She is a scientist who works on innovative approaches like biofilms to understand infectious diseases. Special focus of her lab is to understand the role that microbes and biofilms play in diseases which are relevant to humans. So Utsuka why don’t you go ahead and ask your question to Dr Kaushik.

[08:33] U: So in our previous discussion we learnt that biofilms have so many different microbes like 700 different microbes in our mouth. So our question to you is, ‘how do you actually study these microbes?’

[08:50] K: Great question Utsuka. There are various ways to study that. One thing is the oral cavity has a huge diversity. So we can’t replicate all of this diversity in the lab. One approach we do is, we break it down and take a few relevant microbes based on previous research. The simplest model to study them in the lab is to do them on the bench, the laboratory bench. And so for this we use something called in vitro models. So we grow these microbes on plastic dishes, surfaces. A nice way to make it more relevant to humans is to add factors that the microbes would likely encounter in the human body. So what do you think could be something a microbe encounters in the mouth?

J: Sugar?

[09:31] K: We love fruits, we love chocolate. Coffee. What else can you think of? Different kinds of diets. Differently a whole range of other factors as well. So we can actually add these factors in the lab when we are growing the microbes and study how they behave when they form biofilms. They are simple in the sense that they don’t recap all the factors in the oral cavity but they are interesting enough and they provide some good insights and in an accessible and affordable format. The next step is to make larger and complex models where you can add multiple different microbes, multiple different factors; study the effects of these factors on the microbes, or microbial growth, and biofilms composition over time. Or you can also look at it under the microscope. And then we have advanced models where we can use animals in order to study biofilm infections. Common animals used are mice (rodents). Of course animal models do present a range of ethical concerns, and therefore we should be very judicious and careful in thinking of the kind of experiments we need to do with them.

[10:32] J: How do you get the microbes from the oral cavity?

[10:36] K: So usually Jigyasa we start with the lab grade microbes. We can use clinical samples in case we can access them through mouth washings or screepings or brushing or in certain cases even tissue biopsies. But then you are only sampling one person so it’s not representative of the whole population because I may eat something that you don’t eat.

[10:59] U: So you just now mentioned clinical samples, right? We also know that you were, still are, clinician cum researcher. So how does your background explanation help you do the research that you do now with biofilms?

[11:13] K: Honestly when it comes to my professional trajectory I don’t think I know how to describe myself. But yes, by training and education, I am a medical doctor. And now I work predominantly in the role of running a research group. It is a very exciting journey, right? Lots of wonderful things happened like I discovered my love for research during this time. I also returned to India which was a very deep commitment and motivation I had to come back and contribute to our science ecosystem. How my research differs from possibly many others who are purely scientists in their training, is that I always like to see the bigger picture in mind. I always like to see how this can possibly impact healthcare practices, technologies, and patient welfare. What I feel is I start with the other end. I start with what is the patient’s problem and then try to get that in the lab.

[12:07] U: So you know more about the patients then let us say a researcher who is doing their research in isolation not knowing who the end consumer would be. Right?

[12:19] K: So it happened during my MD in microbiology at Armed Forces Medical College, Pune. I was handed over this MD thesis project. It said we needed to genotype or genetically characterize Varicella zostum, chickenpox. So a lot of young people must have heard of chickenpox. It is something that keeps you in bed for 10 days. So I was given this project to characterize chicken pox strains across India. At that time the armies… again starting with the needs, right? I think this has built my brand of science. This experience also made me recognize that I really love research. I really love to bridge the world between large problems and small problems.

[13:00] J: So what was the biggest one for you to transition from doctor to training into research?

[13:05] K: I think it was about… transitioning to research. If I had to put one thing on it I think I grappled with some of the analysis of the data. Like I could do the experiment. I didn’t have trouble if the experiment didn’t work. Troubleshooting was kind of my thing because medicine is a pretty hard career. For me it was really understanding how to use tools like biostatistics, computational programs, and advanced visual representation of data; so these things I never learnt in medical college or residence. And that’s where undergrads, masters students, research fellows, collaborators have been my assets. So I stopped taking it on that I need to know everything.

[13:59] U: Now that you have gone through that transition, What would be your advice to some high schoolers who are at the brink of making that transition?

[14:04] K: Based on my own learnings, what suggestions I would give is… First, you know, you have come this far and it has not been losing. So I grappled with gaining that confidence in my abilities and skills. And this particularly so when you take big moves like moving across domains and disciplines and countries. Major life changes start to wonder with every rejection that, ‘I am not good enough’, ‘Maybe this is not for me’. We have come this far. We made a big journey to get here and you know.. It is a matter of time till we find our feet again. And the second thing I would say is once you have found your feet and you are enjoying what you are doing. Just keep staying excited about what you are doing. It is truly a privilege to be able to get up every day only and saying that my job description is to think and execute ideas. Passion alone is not going to pay the electricity bill. And just a job for money is not going to fulfill all your dreams and ideas that keep coming up. So these two worlds can meet. Like in my present role, research pays the bill. Because that’s where I draw my salary from. But the questions that I ask can be clinical. So while I am not practicing medicine and I don’t see patients everyday and write prescriptions everyday, I am still using my knowledge and the ideas that come from my clinical training.

[15:21] J: Thank you so much for spending your time with us for this interview and it has been lovely chatting with you and super inspiring.

[15:32] U: So do you now get why we have cavities?

J: Yes, our teeth are covered by biofilm, a matrix in which various microbes live. When we eat loads of sugar, the microbes in the biofilms convert the sugar into acids. And this creates an imbalance that also degrades our tooth enamel. This causes cavities.

[16:00] U: Exactly. We also asked Dr Kaushik about how scientists study these microbes and she said that researchers just grow important microbes in petri dishes and feed them food. Let’s say coffee. Or study microbial interactions in model organisms like rats.

J: Yes, and she also spoke about the perks of being a physician scientist as she can combine the best practices of the two worlds.

U: But listeners, what we know about biofilms might change over time.

J: Who knows one of our listeners would study about biofilms and find out something that we never knew before!

U: So that’s it for today.

J: If you want to know more about today’s scientist, we have linked his profile in the Show Notes!

U: If you have any questions that you want us to explore, shoot them away to Indiaakswhy@gmail.com

J: If you'd like to directly talk to us directly, then join the fun, join the fun on our Telegram Group. Link in the show notes.

U: For updates on IndiaAsksWhy, follow us on @IndiaAsksWhy on Twitter, and @India_AsksWhy on Instagram.

J: Shweata N. Hegde and Ruchi Manglunia are the hosts for the podcast.

U: Indulekha M.S. edited this episode.

J: And Khushi Goel transcribed it.

U: and we are funded by the indiabioscience’s second outreach grant.

J: Until next time! Till then, stay tuned and stay curious.