Dr. Tim Johnson

Assistant Professor of Food Animal Microbiome. Tim obtained his B.S. at Brigham Young University and his PhD at the Center for Microbial Ecoogy at Michigan State University. His PhD research focused on microbial ecology in soil, animals and manure. His PhD work provided a quantitative measure of diverse impacts of in-feed antibiotics on bacterial community membership and antimicrobial resistance genes. After earning his PhD, Tim found his first postdoc position at McMaster University in Ontario, Canada where he investigated antimicrobial resistance and drug discovery. In a second postdoc at the National Animal Disease Center, he used multi ’omics (metagenomics, metabolomics, metatranscriptomics, and 16S community profiling) approaches to studying the swine and turkey microbiome in efforts to find alternatives to antibiotics in animal agriculture.


Tim and Angela Johnson have 6 children – Zach, Grant, Bennett, James, Mary and Ruby. As a family, they enjoy soccer, music, basketball, hiking, camping, swimming, running, and DIY projects at home. 

PhD Students

Paul Oladele

I completed my undergraduate in Nigeria in the department of Animal Production and Health at Ladoke Akintola University of Technology. During this degree, I had the opportunity of working in a reproductive physiology laboratory where I examined the effect of some feed ingredients on the reproductive system of rabbit bucks. This instigated my interest in research. I later completed a master’s in animal breeding in the department of Animal Sciences at the University of Ibadan. After working in the agriculture and nutrition industry for a few years, I returned to the laboratory of Dr. Kola Ajuwon in the department of Animal Science at Purdue University to explore the potential role of nutrition on the metabolism and the immune system. During this period, I realized that the complex community of microbes in the gut modulates the effect of diet of their host. I was excited when the opportunity came to explore the role of these complex microbes in the development of diarrhea in piglet with Dr. Tim Johnson. I hope that results can provide more insight into the role of gut microbiome in normal health and disease which could then be used to develop microbial therapy for post weaning diarrhea in piglets.

Eunice Centeno-Martinez

Eunice is originally from San Salvador, El Salvador, and in 2018, she received her bachelor’s degree in Agricultural Science from Zamorano University in Honduras. During her undergrad, Eunice joined Dr. Johnson’s lab as an intern and worked in a collaborative study analyzing the effect of in-feed glutamine and antibiotics in the piglet's ileum microbiome postweaning and transport. In 2019, she returned to Purdue University to get her Master's with Dr. Tim Johnson. During this time, Eunice’s research focused on characterizing the respiratory microbiome, specifically bacteria, of cattle diagnosed with Bovine Respiratory Disease (BRD) with the purpose to identify any possible diversity value that could be used as a potential method to diagnose cattle with BRD. After obtaining her Master’s degree in May 2021, Eunice stayed at Dr. Johnson’s lab pursuing her Ph.D. degree. Now as a Ph.D. student, she will continue researching in the area of Bovine Respiratory Disease, but including the characterization of viruses, fungi, and bacteria that might interact in the nasal cavity of healthy and BRD affected animals. 

Eunice is also a member of the Association of Zamorano Alumni  (AZA) at Purdue in which she served as the treasurer in 2020. Currently, Eunice serves as the President of the Association of Zamorano Alumni at Purdue and as the National Secretary of the Association of Zamorano Alumni in the US. Eunice enjoys dancing, playing sports, and signing, and she identifies herself as a cattle and microbiome lover, so working in this lab is a dream come true. 

Wenxuan Dong

Wenxuan comes from China, Shandong Province. Wenxuan obtained his B.S. and M.S. at China Agricultural University where he focused on nutritional evaluation of feed ingredients in pigs. His PhD work at Purdue will focus on the interactions between gut microbiome and animal performance. He will combine multi’ omics approaches and classical husbandry technology to find the optimal intestinal microbial consortium to promote the health and production of animals.      

Masters Students

Tessa Sheets

I joined the lab in 2019 and my undergraduate work was mostly comprised of analyzing bacterial communities using 16S RNA gene sequencing. My previous projects include characterization of the bull semen microbiome (published) and identifying the effects of genetic line and Salmonella challenge on the broiler intestinal microbiome (submitted for publishing). My thesis involves the use of machine learning to determine genotypic and phenotypic concordance between Pasteurella multocida isolates from BRD cattle. I have presented research at several conferences such as the Purdue Undergraduate Research Expo (Fall 2020 and Spring 2021), the 2021 Beyond Boundaries Symposium for the Indiana Branch of the American Society for Microbiology (ASM), and the 2022 ASM Microbe Conference in Washington D.C. I was a recipient of the 2020 CATE Faculty Research Grant and earned highest distinction for my bachelor’s degree in Animal Science. I grew up on an alpaca farm which has recently expanded to include lowline Angus cattle. My hobbies/interests include pole vaulting (Purdue Varsity Track and Field alumna), skincare, and watching reality TV.

Undergraduate Students

Tiffany Chang 

Tiffany is an undergraduate student at Purdue University majoring in Animal Sciences with a concentration in Pre-Veterinary Medicine. In addition to undergraduate research, Tiffany is involved with various student organizations at Purdue, such as the Asian American Association. Tiffany plans on becoming a small animal veterinarian in the future. 

Erica Long

Erica is an undergraduate student from New Palestine, Indiana studying Animal Sciences with a concentration in Biosciences, in hopes to become a research scientist. She joined the lab in the fall of 2021 and is currently working with Eunice on her PhD project. Outside of classes, Erica is a member of the Purdue Swim Club and Poultry Club. She also enjoys cake decorating, making art, reading, and listening to podcasts.

Congratulations and best wishes to Wenxuan. He successfully defended his Master's thesis this month and will go to University of Wisconsin to begin his PhD program! He has made a massive contribution to our lab!

On August 27th 2021, after a year and a half of online meetings, we were able to hold our weekly Lab meetings in person at Creighton Hall! We are excited for the start of a great semester!

On August 13th 2021, the lab had a great post summer potluck. Everyone brought all different types of food and it was alot of fun!