Understanding how Populations Spread

Work done in the lab of Prof. Terry Hwa at the University of California, San Diego

About author

Avaneesh Narla was raised in Bengal, Telangana, and Maharashtra, close to nature, and has always been curious. He studied physics, mathematics, and computer science at Princeton University for his Bachelor’s degree and is now a Ph.D. Candidate at the University of California, San Diego. He is interested in questions in theoretical ecology, population biology, and collective behavior. He particularly likes tackling technical mathematical problems to derive general principles that govern biological phenomena. He also finds great meaning in teaching and has been the lead instructor for introductory physics courses at UCSD and conducted quantitative and qualitative pedagogical research. He is particularly interested in developing interdisciplinary courses and student-centered science classrooms. In his free time, he likes to read scientific non-fiction, watch nature documentaries, hike mountains, and explore urban neighborhoods.

Interview

How would you explain your research outcomes to the non-scientific community?

As a fundamental part of their life cycle, bacteria spread by dispersing into new habitats. We have all experienced this with food in our kitchen that gets spoiled. Bacteria navigate these new habitats by sensing changes in the availability of nutrients around them. These changes are often generated by the bacteria themselves as they consume the nutrients. In our paper, we mathematically studied how bacteria consume nutrients and spread rapidly in the environment as a result. We are able to understand how the spread depends on core bacterial and environmental characteristics, like the growth rate, the abundance of nutrients in the environment, and the detection limit of the nutrients.

How do these findings contribute to your research area?

The spreading of bacteria in distinctive patterns has been observed in experiments for over 50 years. However, nobody was able to explain this spread mathematically. This meant that the community didn’t understand how fast the spread took place and what the rate of spread depended on. We were able to answer these questions so researchers can make predictions for their systems. But perhaps more importantly, once we understood the process, we realized that it was not unique to bacteria. Because of how common this process is, we believe that the way bacteria spread is also how higher-order organisms such as wolves and birds spread.

What was the exciting moment during your research?

The set of equations that describe the spread of populations that sense their environment are quite complicated. We struggled for a long time to find techniques to study them. At one point, we noticed something peculiar, and we made a guess as to why that was the case. The guess worked and allowed us to understand the entire system as a result! In fact, armed with this insight, understanding the rest of the system turned out to be relatively easy. This sudden and unexpected breakthrough was very exciting.

What do you hope to do next?

There are many applications of the understanding we developed for population spread that I want to get to. But right now, we discovered something exciting in a completely different field of biology that has our attention. In simulations of microbes growing together, we observe many species sharing a few nutrients without one outcompeting the others. This is surprising since Darwin’s idea of “survival of the fittest” might lead one to think that only one would survive. However, it turns out that all these species can be the “fittest” in their own way. This result challenges a lot of long-held ideas in the field. We are looking forward to sharing this with the community.

Where do you seek scientific inspiration from?

I read a lot of popular science books and articles. I find it fascinating to learn about developments and insights in other fields. I do not characterize myself as a physicist (in fact, I hardly do research in traditional physics) but as an interdisciplinary questioner and hope to ask questions in other fields in my career. Learning about other fields both inspires me to look deeper into my field and also gives me intellectual ideas that I try to explore in my own research.

How do you intend to help Indian science improve?

I intend on moving back to India after completing my training abroad to teach and do research. I am especially interested in training the next generation of thinkers and researchers in India. Research in India is booming, and I hope to be a part of the drastic advancements taking place. Also, in the past higher education in India has been primarily vocational but there are now changes where the focus of education in certain institutions has been to develop critical thinking in students. I hope to be a part of this change.

Reference

Avaneesh V. Narla, Jonas Cremer, Terence Hwa. A traveling-wave solution for bacterial chemotaxis with growth. Proceedings of the National Academy of Sciences Nov 2021, 118 (48) e2105138118.

Edited by: Pratibha Siwach

Meet the managers

Surabhi Sonam

Surabhi Sonam is an Assistant Professor. Along with teaching and research, she has a very strong interest in science communication. She has written several poems and blogs to communicate scientific principles and concepts. She is also volunteering with several science communication platforms as a content contributor and content editor. Under her supervision, her students have launched a scicomm magazine, Scinion which represents science in verbal and visual forms.

Sejal Dixit

Sejal Dixit is currently a 3rd-year student pursuing BSc triple majors in biotechnology, zoology, and chemistry from CHRIST (Deemed to be University). She loves to read, be it short stories, novels, magazines, or research articles. She is working with her college professor on a few papers, and wishes to pursue her master’s degree in stem cells and regenerative medicines. She has no problem socializing with new people and possesses leadership qualities. Her hobbies are dancing and traveling.

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