Joseph P. Zackular, Ph.D.

Principal Investigator
Assistant Professor of Pathology and Laboratory Medicine
Co-Director, Center for Microbial Medicine
Division of Protective Immunity
University of Pennsylvania
Children's Hospital of Philadelphia

B.S. - University of Massachusetts - Amherst, 2008
M.S. - University of Massachusetts - Amherst, 2009
Ph.D. - University of Michigan, 2014 - (Dr. Patrick Schloss Lab)
Postdoc - Vanderbilt University - (Dr. Eric Skaar Lab)

Joe is originally from North Reading, Massachusetts and he received his B.S. and M.S from The University of Massachusetts-Amherst. He earned his Ph.D. in Microbiology & Immunology from the University of Michigan in the laboratory of Dr. Patrick Schloss, where he studied the role of the gut microbiome in colorectal cancer. Joe did his postdoctoral training in the laboratory of Dr. Eric Skaar at Vanderbilt University where he studied the impact of nutritional immunity and dietary metals on Clostridioides difficile infection.

Rochelle Glover

Postdoctoral Fellow

Rochelle is originally from Portland, OR and attended Oregon State University for her B.S. in Microbiology. She obtained her Ph.D. in Microbiology at the University of Washington where she studied interactions between the intracellular pathogen Listeria monocytogenes and inflammatory phagocytes. In the Zackular Lab, she is integrating her interests in bacterial physiology, microbial pathogenesis, and the host response by studying how C. difficile responds to changes in the host environment. Outside of lab Rochelle pursues many hobbies, including gardening, baking, roller skating, and watching reality tv.

Haider Manzer

Postdoctoral Fellow

Haider received a B.S. and M.S. from the University of South Florida in biomedical sciences and cell and molecular biology, respectively. During his time at USF, Haider investigated the manipulation of bacterial epigenetic factors in Actinobacteria to produce novel antibiotics for the treatment of multi-drug resistant pathogens. He then completed is doctoral thesis characterizing factors at the host-pathogen interface contributing to Group B Streptococcus colonization and disease. As a postdoctoral fellow in the Zackular Lab, Haider is excited to investigate C. difficile infection dependent epigenetic remodeling of the colonic epithelium from early life to adulthood, and is also interested in the pathogenic synergy between C. difficile and common neonatal pathogens. Haider aims to become a microbiology professor and PI of an academic lab that investigates both host and bacterial mechanisms that contribute to pathogenesis. Outside of the lab, Haider enjoys hiking, snowboarding, and playing boardgames.

Connor Tiffany

Postdoctoral Fellow

Connor grew up in San Jose, California and received his B.S. in Biological Sciences from the University of California, Davis. He then completed his PhD under Dr. Andreas J. Bäumler at UC Davis, where he developed a framework combining computational and wet-lab approaches to uncover nutrient niches within the gut microbiota. During his post-doc in the Zackular lab, Connor plans to continue using wet and dry-lab methods to investigate how the host drives gut microbiota community assembly in early life, and to determine the ecological relationships between commensal Enterobacteriaceae and Clostridiodes difficile in the gut and their effects on pathogenesis. Connor plans to eventually become a PI at a medical school where his lab would tackle questions involving the gut microbiota in human health and disease. Outside of science, he likes to spend his time painting, printmaking, 3D printing, and doing any number of DIY projects.

Nicolas (Nic) Gray Shealy

Postdoctoral Fellow

Nic is originally from Columbia, SC, and received his B.S. from the College of Charleston (Go Cougars!). He earned his Ph.D. in Microbe-Host Interactions from Vanderbilt University in 2025, under the mentorship of Mariana X. Byndloss, DVM, Ph.D., where he studied the role of amino acid metabolism in the colonization and susceptibility to the enteric pathogen Salmonella enterica sv. Typhimurium. In the Zackular lab, he is combining his interests in pathogen metabolism and microbial ecology to understand and define the signals used by C. difficile to switch lifestyle during asymptomatic carriage and acute disease. Outside of the lab, Nic enjoys watching horror movies, playing board games, and new art projects, from knitting/crocheting to painting.

Kassy Donohoe

Research Technician

Kassy graduated with an Honors B.S. in Pre-Veterinary Medicine from the University of Delaware in 2024. During her undergraduate years, she realized the importance of veterinary medicine in not only protecting the health of animals but the health of humans as well. Kassy is passionate about studying microbiology, immunology, and virology in the context of One Health. She is particularly interested in exploring how animal and environmental health factors influence the transmission and pathogenesis of human infectious diseases identified as public health concerns. Kassy is excited to dive deeper into the microbiology and immunology research world and develop herself as a scientist.

Joshua Soto Ocaña

Graduate Student (CAMB-MVP)

Josh is originally from Puerto Rico where graduated from the University of Puerto at Mayagüez in 2018 with a B.S. in Industrial Microbiology, a B.S. in Biology, and a minor in Biochemistry.  While his undergraduate research was focused on organic chemistry and biochemistry, he was always very passionate about infectious diseases. In the Zackular lab, Josh straddles the line of basic bacteriology and epithelial cell biology studying how pharmaceutical drugs and the microbiota impact Clostridioides difficile pathogenesis. When he is not at the bench he enjoys going to the beach, baking, biking, and working out.

Orlaith Keenan

Graduate Student (CAMB-MVP)

Orlaith graduated from the University of California, Santa Barbara in 2019 with a B.S. in Microbiology. As an undergrad, Orlaith worked at Apeel Sciences where she isolated fungal pathogens and screened potential antifungals. Orlaith later joined the Zackular Lab as a technician, studying the interactions between the infant microbiome and C. difficile. Now as a grad student in the Microbiology, Virology, and Parasitology program, Orlaith is excited to continue exploring the dynamic microbial interactions in the gut.

Twitter: @OrlaithKeenan

Rinnie Hewlett

Graduate Student (CAMB-MVP)

Originally from Maryland, Rinnie graduated in 2021 with a B.A in Biology from Brown University. As an undergrad, she studied the response of the microbiome to external factors such as antibiotics and diet in the lab of Dr. Peter Belenky. This included a project exploring how instant coffee affects the mouse microbiome during antibiotic treatment. She’s excited to continue exploring microbial interactions in the context of C. difficile infection. When she’s not in the lab, Rinnie enjoys biking, crocheting, and adding new books to her TBR.

Ashley Weiss

Graduate Student (CAMB-MVP)

Ashley earned her B.S. in Cell Biology and Molecular Genetics from the University of Maryland in Spring 2022. At UMD, she worked with Dr. Brantley Hall to investigate gut microbial metabolism in the context of neonatal disorders and inflammatory bowel disease. Ashley also undertook research and internship positions at the NIH, Merck, and the World Resources Institute. She was excited to return home to the Philadelphia area in Fall 2022 to begin her Ph.D. training in the Microbiology, Virology, and Parasitology program in the Cell and Molecular Biology graduate group at the University of Pennsylvania. In the Zackular lab, Ashley continues to explore her interest in the gut microbiome by studying polymicrobial interactions and metabolic remodeling during C. difficile infection. She is also involved in the Graduate Training in Medical Science (GTMS) certificate program at Penn and was offered an award for the 2024 National Science Foundation Graduate Research Fellowship Program (NSF GRFP) in microbial biology. Outside of the lab, Ashley enjoys making artwork, playing tennis, trying new restaurants, and spending time outdoors.

Qianxuan (Sean) She

Graduate Student (CAMB-MVP)

Sean graduated in 2017 with BSc from Lanzhou University in Lanzhou, China. As an undergrad, he identified the species of bacteria that lived within the bulbs of Narcissus, and it planted the seed for his passion for bacteria. He received his master’s degree in 2020 from Northeastern University in Boston. During his master’s, he worked in Dr. Yunrong Chai’s lab, where he investigated the interplay between biofilm formation and competence in Bacillus subtilis. He also worked with E. coli and Vibrio cholera before he eventually found his true passion. He switched to dry lab and currently uses bioinformatic tools to study the impact of early life colonization and transmission of pathogens on health and disease.

Tiffany Zhou

Graduate Student (CAMB-MVP)

Tiffany grew up in Charlotte, North Carolina and graduated from Vanderbilt University with a B.A. in Biochemistry and Chemical Biology in 2024. As an undergrad, she worked in the lab of Eric Skaar, where she investigated zinc and copper homeostasis in Acinetobacter baumannii. As a part of DAAD-RISE, she also briefly worked at the Max Planck Institute of Terrestrial Microbiology in Marburg, Germany, where she used optogenetic approaches to study type III secretion systems in Yersinia enterocolitica. In the Zackular Lab, Tiffany is excited to study the long-term impact of neonatal C. difficile colonization and mechanisms mediating neonatal resistance to infection. In her free time, she enjoys crocheting and playing violin in the Penn Med Symphony Orchestra.

Amanda PeBenito, M.D.

Clinical Fellow

Amanda is currently a Gastroenterology fellow in the University of Pennsylvania Hospital system.  She is on the T-32 basic science track and completing her research years in the Zackular lab.  Her clinical interest is in Inflammatory Bowel Disease and she is excited to explore why this patient population is particularly susceptible to C. difficile infection.  She completed her residency in Internal Medicine at Massachusetts General Hospital where she was a member of the Stanbury Physician-Scientist Program.  Amanda received her M.D. from NYU School of Medicine, where she worked in the lab of Martin Blaser studying the role of the microbiome in preventing kidney stones and graduated with an Honors in Research.  She completed her undergraduate studies at Columbia University and graduated with a B.A. in Biology and Latino/a Studies.  She joined Teach For America and spent three years teaching high school science in the Bronx between undergrad and medical school, and earned a Masters in Science Education during that time.  She is planning for a career in academic medicine that will include treating patients with IBD and conducting research on the pathophysiology of the disease, while educating and mentoring trainees in medicine and research. 

Jibraan Fawad, MBBS

Clinical Fellow

Jibraan is a Pediatric Gastroenterology fellow at the Children’s Hospital of Philadelphia. He grew up in Karachi, Pakistan where he went to medical school at the Aga Khan University. Prior to starting pediatric residency, he worked under the mentorship of Sean Moore at the University of Virginia identifying mechanisms by which microbial metabolites modulate host intestinal circadian rhythms. He also developed models to study environmental enteropathy and malnutrition. He completed his pediatric residency in Kalamazoo, Michigan and was a chief resident at his program. He is completing his research fellowship in the Zackular lab where he aims to define mechanisms by which nutritional interventions alter C. difficile pathogenicity and outcomes of infection. His clinical interest is in inflammatory bowel disease and he is pursuing an academic career where he hopes to treat patients by leveraging nutrition and the microbiome as potential therapies to treat GI pathologies.

Hannah Srey

Undergraduate Student

Hannah, a Philadelphia native, is an undergraduate student at the University of Pennsylvania studying Biology with a concentration in Mechanisms of Disease, as well as pursuing a minor in Sociology. Hannah’s aspirations are to pursue a career in immunology and microbiology, aiming to bridge the gap for Southeast Asians’ access to equitable healthcare. She also hopes to work towards addressing disparities in access and outcomes for underserved communities. She is a PennFERBS fellow, which is a program that strives to bridge the gap between underserved communities in biological research. In the Zackular lab, Hannah is excited to learn more about microbiology and its interactions within the gut microbiome. Beyond her interest in the sciences, Hannah is an avid concert-goer, baker, reader, napper, and lover of her two cats.

Beaker

Website manager
Emotional support dog

Beaker is from Kalamazoo, Michigan.  He's 9 years old and when he's not in the lab he is usually sleeping, barking, or eating. His favorite thing to do is go on long walks and chase squirrels.

Erlenmeyer

Creative design engineer

Erl is originally from Nashville, Tennessee.  He's 2 years old and when he's not in the lab he loves watching birds, playing with his brother, and meowing at the wall.  
 

Gretchen

Grants administration

Gretchen enjoys sitting in the sun and chasing strings.

Nala

Director of animal research and pioneer of the C.difficile infection model

When not pursuing her passion for interior design (rearranging her toys, unfolding blankets, and occasionally burrowing into a box spring), she enjoys sitting on the couch and demanding pets.

Azula

Reviewer #2

Mia

Lab Yapper

Mia has traveled cross country twice, and been in a plane at least three times. When she isn't traveling, she loves talking to everyone and taking naps. You can usually find her guarding the stairs or chasing bugs in her free time.

Tommy

Lab Napper

Tommy is originally from a barn in Lancaster, PA. He loves naps and can usually found on his back in the sun. His favorite past times include cuddling and eating treats from the cabinet.