Unraveling the Mysteries of the Fungal Microbiome

Judith Behnsen’s fascination with pathogens led her from Germany to California and finally Chicago. Now a microbiologist at the University of Illinois, Chicago, she combines her passion for fungi and her love of infectious disease, studying how commensal microbes in the gut interact with the Salmonella pathogen to shape the course of infection.

Why did you want to become a scientist?

My biology teacher in high school was the one who spurred my interest in science. She loved teaching us about the lac operon in E. coli and other aspects of molecular biology. I loved those topics, too, and I wanted to learn more about how cells and bacteria function and why we get sick, so I decided to study biology in college.

What sparked your interest in infectious disease research?

I always had a love for everything small and the things that you can’t see, especially bacteria. My mom says that even as a child, going for walks with me was very difficult because I would plop down on the ground and examine the soil. I guess I loved small things from the beginning! At the University of Hannover, where I earned the German equivalent of a combined bachelor’s and master’s degree, the coursework was focused on diseases and microbiology, and most of the research that I was exposed to was about pathogens. That’s when my love of infectious disease started to grow.

At the end of my program, I did nine months of research with Axel Brakhage, a microbiologist studying the fungus Aspergillus fumigatus, and I loved it so much that I stayed in the same lab for my graduate work. A bacterium usually just divides and then divides again, but a fungus is much more complex. I found that fascinating.

A. fumigatus can cause infections in immunocompromised individuals, but it is not a true pathogen, so after finishing my PhD I found a postdoctoral position working on Salmonella in Manuela Raffatellu’s lab at the University of California, Irvine. Once there, I began to learn about the microbiome and its functions. I started to think more about commensal microbes, and during that time, the first high-impact papers on the fungal microbiome began to come out. I realized that I could combine my two areas of interest, and for my first R01 research grant I proposed studying the role of the fungal microbiome during Salmonella infections.

Why did you decide to stay in academia and start your own lab?

It might seem a little bit weird now, but becoming a professor was never on the forefront of my mind. In Germany, I didn’t have a lot of role models—female professors were few and far between. I didn’t actively think about it back then, but passively you observe that and internalize it. Honestly, I was not confident that I would make it to a professor position.

Things changed in the US, because I saw how successful Manuela was. She was very encouraging, and it was a lot of fun talking with her and developing research directions. Over time, my confidence in my abilities grew, I got involved in grant writing, and more ideas came. I asked myself, can I do this? I learned the term imposter syndrome mid-way through my postdoctoral research and thought, that is me! I didn’t know that other people felt the same way. It was so enlightening to know that I wasn’t alone and that other people felt that way, too. That was very helpful.

What do you see as some of the most exciting possibilities in your field?

I am very interested to see if what we find in the lab actually matters in the clinic. Take, for example, our recent publication in which we showed that the presence of Candida albicans worsens Salmonella infections.¹ When an immunocompromised person is infected with Salmonella Typhimurium, there is an increased risk of dissemination to peripheral organs, so doctors prescribe an antibiotic. However, the antibiotic will also kill part of the bacterial gut microbiome, which leaves a space in the gut. If you are colonized with C. albicans, the population will expand, and based on our findings, that could worsen the disease. It may be that C. albicans is an underappreciated risk factor for disseminated Salmonella infections in people, but we simply don’t have any data on that yet. So far, nobody has looked.

This interview has been condensed and edited for clarity.