Meet the Team

Julia Willett, PhD Assistant Professor 

I grew up in central Illinois and graduated from the University of Illinois at Urbana-Champaign in 2010.  I earned my PhD with Dr. Chris Hayes at the University of California, Santa Barbara, where I studied contact-dependent bacterial inhibition systems in Gram-negative bacteria and was supported by an NSF Graduate Research Fellowship.  I came to the University of Minnesota for postdoctoral research with Dr. Gary Dunny, where I was supported by an NIH T32 in Lung Science, an American Heart Association postdoc fellowship, and an NIH K99/R00.  I am interested in discovering the function of uncharacterized bacterial genes (bacterial "dark matter"), mechanisms of polymicrobial interactions and interbacterial competition, the underlying genetics of biofilm formation, and understanding how Enterococcus faecalis establishes and persists in the gastrointestinal tract.  I am so excited to be starting my own lab where I will get to do cool science and train/mentor the next generation of researchers!

LIKES:  cats, K pop, Selling Sunset, Cheez-Its

DISLIKES:  mayonnaise


Ruth Isenberg, PhD NIH K12 IRACDA Postdoc Fellow

I was born and raised in the Pacific Northwest near Tacoma, Washington. I graduated from the University of Puget Sound with a BS in Molecular and Cellular Biology in 2016. I earned my PhD in Microbiology from the University of Wisconsin-Madison in 2023 in Dr. Mark Mandel’s lab where I studied cyclic diguanylate regulation of beneficial host colonization using the Vibrio fischeri-Hawaiian bobtail squid symbiosis as a model system. In the Willett lab, my research focuses on investigating the mechanisms that underlie Enterococcus faecalis killing by Streptococcus mutans. My goal is to become a professor at a primarily undergraduate institution where I can continue teaching and mentoring undergrads in the classroom and the lab!

LIKES: knitting/crocheting, seafood, video games, reality TV

DISLIKES: untangling yarn

Grad Students

Amanda Haeberle, MS Microbiology, Immunology, and Cancer Biology PhD Program

I grew up in northern Colorado and graduated from the University of Colorado Boulder where I studied Molecular Cellular and Developmental Biology and graduated in 2018. After a brief sabbatical from school, I returned back to school in 2020 to the University of Colorado Anschutz Medical Campus where I studied small RNA mediated gene regulation in Group B Streptococcus in Dr. Kelly Doran's lab. I graduated with my master's in 2022 and then moved to Minnesota to pursue my PhD in microbiology at the University of Minnesota. I am interested in host-pathogen interactions, polymicrobial interactions and bacterial pathogenesis. 

LIKES:  cats, wine, pandas, elephants and cheese

DISLIKES:  olives and mushrooms 

Carlo Castillo Microbiology, Immunology, and Cancer Biology PhD Program

I am from the Chicago area and graduated from The Ohio State University with a BS in Chemistry in 2017. Post-graduation I spent a year volunteering at a refugee resettlement agency in Denver, CO teaching workforce readiness classes. From 2018-2020 I was a postbac research fellow at the NIH in the lab of Dr. Ian Myles, where I studied the skin commensal bacterium Roseomonas mucosa and its role in atopic dermatitis. In 2021 I began my PhD in Microbiology at the University of Minnesota, and I am interested in microbial ecology, host-pathogen interactions, and co-culture models. 

LIKES: hiking, fishing, camping, taquerias, Tottenham Hotspur FC

DISLIKES: billionaires

Lab Technicians

Emily Carson, MS

I graduated from St Olaf College, where I researched biofilm formation in Pseudomonas aeruginosa, in ‘22 and just finished my Masters in Biomedical Sciences at Vanderbilt University in August of ‘23. At Vanderbilt, I investigated the role of transcriptional regulation in the proliferation of cardiovascular inflammation which is thought to play a role in the development of atherosclerotic plaques. I am now working in the Willett Lab to investigate biofilm development in simulated wound conditions and in the presence of various antibiotics. 

LIKES: scary movies, reading, hiking, energy drinks, cats

DISLIKES: ice (in drinks and outside)

Alex Snell, BS

Erna Karic, BS

I was born and raised in Minnesota, though my family is from Bosnia and Herzegovina. In 2024, I graduated from the University of Minnesota with a BS in Microbiology. As an undergrad, I worked in the Willett lab investigating understudied species of Enterococcus isolated from dirt samples in Minnesota by conducting growth curves and biofilm assays, as well as preparing DNA for sequencing. After graduation, I transitioned to a Lab Technician position, where I am now delving into pigment production and function in Enterococcus mundtii

Likes: nature, animals, crafting

Dislikes: pickles, chewing sounds 

My research endeavors have been assisted by my service animal, Nemo. He is a golden retriever/poodle mix and is about 5 years old. He is owner-trained. 

Likes: eating, cuddling, swimming, playing (in that order)

Dislikes: popping sounds, heat 


Jenny Geng

I am currently a junior at the University of Minnesota studying biochemistry with minors in health psychology and mathematics on a pre-medical track. I grew up in Iowa City, Iowa. The project I am working on for the Willett lab involves studying E. faecalis biofilm formation in simulated wound conditions, and I am really excited to explore this further!

LIKES:  the outdoors, Gilmore Girls, swimming, reading, ducks


Faduma Mohamed Undergraduate Researcher

Celine Sackih Undergraduate Researcher

I am a second-year undergraduate student at the University of Minnesota, majoring in Genetics, Cell Biology, and Development. I hope to eventually declare a minor in English and continue onto pharmacy school after undergrad. The main project I'm working on in the lab is investigating the expression of the gelatinase protease in E. faecalis.

LIKES: crocheting, podcasts, pho, pink, and weighted blankets

DISLIKES: cottage cheese and spiders

Sarah Zar Undergraduate Researcher

I'm from St. Louis, MO and moved up to Minneapolis to attend the University of Minnesota, where I'm currently a junior majoring in microbiology.  I'm currently investigating biofilm formation in antibiotic-resistant mutants that arose from E. faecalis isolated from blood or prosthetic joint infections.  I'm excited to keep learning new techniques for studying bacterial genetics and biofilm formation as I continue to explore my interests within microbiology!  Outside of the lab, I enjoy cooking, watching sports, and checking out different parks and lakes near Minneapolis.

Lab Mascots


Louis Pasteur

Lab Alumni