Jonathan P. Jacobs, MD, PhD
Director, Microbiome Core, UCLA Microbiome Center
Principal Investigator

Dr. Jacobs is a gastroenterologist and scientist studying the role of intestinal microbes in digestive diseases. He graduated magna cum laude with highest honors from Harvard University with an AB in biochemistry. He subsequently received his MD from Harvard Medical School, graduating magna cum laude in a special field. During college and medical school, he trained in an immunology laboratory studying rheumatoid arthritis with funding from the Howard Hughes Medical Institute. He completed a residency in internal medicine at Stanford University then joined UCLA to pursue gastroenterology training in the Specialty Training and Advanced Research (STAR) program. He was awarded a PhD in Cellular and Molecular Pathology for his IBD microbiome research under the mentorship of Jonathan Braun and afterwards joined the UCLA Vatche and Tamar Division of Digestive Diseases faculty. He co-founded the UCLA Microbiome Center in 2015 and now directs the Microbiome Core, which provides a comprehensive suite of microbiome-related services to support microbiome research by the UCLA scientific community. His research has been published in a wide range of scientific journals including Gastroenterology, Proceedings of the National Academy of Science, Cellular and Molecular Gastroenterology and Hepatology, Microbiome, Gut Microbes, and Scientific Reports. Ongoing projects in his laboratory employ animal models and multi’omics analysis of patient cohorts to define the role of microbes and their products in IBD, obesity, colon cancer, irritable bowel syndrome, and other diseases.

David Meriwether, PhD
Project Scientist

Dr. Meriwether received his PhD in molecular and medical pharmacology from UCLA. After three years of post-doctoral training in the laboratory of Drs. Srinu Reddy and Alan Fogelman, Dr. Meriwether joined the Division of Digestive Diseases in July 2021 as a project scientist affiliated with the laboratories of Drs. Jonathan P. Jacobs and Martin Martin. Dr. Meriwether is an intestinal epithelial and inflammation biologist who investigates the etiology and pathogenesis of inflammatory bowel disease. He has focused in part on the how dysregulation of lipid inflammatory signaling can disrupt intestinal immune tolerance by altering macrophage resolution function and intestinal epithelial repair. Dr. Meriwether makes extensive use of mass spectrometry in his studies, and he is working to build simplified models of the intestinal epithelial inflammatory microenvironment using patient-derived intestinal epithelial organoids.

Carra A. Simpson, PhD
Postdoctoral Fellow

Dr. Simpson is a postdoctoral scholar from Australia who enjoys all aspects of gut-brain axis science, including preclinical mechanistic research, management of large patient cohorts, and data analysis using integrative systems biology. Dr. Simpson studied psychological sciences in her undergraduate degree, followed by a graduate certificate in biomedical sciences when she discovered her passion for microbiome research. Her honors research examining associations between inflammation, cortisol, and the oral microbiome in mediating anxiety and depression symptoms was awarded top thesis in her program and a national APS Prize. During her PhD at the University of Melbourne, she investigated the gut and oral microbiomes in a large cohort of individuals with irritable bowel syndrome, anxiety and/or depressive disorders. In her postdoctoral research with the Jacobs Laboratory, Dr. Simpson leads two projects examining the role of the gut-brain axis in mediating stress-induced inflammatory bowel disease flares (using gnotobiotic models and a human cohort study) and also provides bioinformatics expertise and analysis as part of the UCLA Microbiome Core.

Georgina Xanthou, PhD
Visiting Scientist

Dr. Xanthou completed her undergraduate studies at the University of Athens in the Department of Biology and received her PhD in immunology from the University of Athens, Medical School. Dr. Xanthou performed her post-doctoral studies at the Leukocyte Biology Section in Imperial College as an EMBO-funded research fellow, wherein she delineated novel molecular mechanisms through which Th1 cell-associated chemokines regulate Th2 cell-driven allergic responses. Dr. Xanthou is an associate professor at the Biomedical Research Foundation of the Academy of Athens. The research studies of her group are focused on understanding the mechanisms through which immunoregulatory cytokines control Th cell differentiation and pathogenic functions in allergic and autoimmune diseases. Dr. Xanthou’s studies have been published in leading scientific journals, including Nature Medicine, Science, PNAS, Journal of Experimental Medicine, Journal of Allergy and Clinical Immunology and American Journal of Critical Care Medicine. For her research studies, she has received numerous awards by prestigious research entities. Dr. Xanthou has recently joined Dr. Jacob’s lab as a visiting associate project scientist and her studies are focused on how the microbiota shape immunological responses and linked inflammatory processes in mouse models of inflammatory bowel diseases.

Carolina Koletic, MD
Pediatric GI Fellow

Dr. Koletic earned her bachelors of science degree in anthropology at UCLA and her medical doctorate degree at the University of Zagreb School of Medicine. Since college her passion has been to help children manage chronic disease so that they may fulfill their potential as adults. She is an active volunteer since 2007 at Camp Conrad Chinnock, a youth type-1 diabetes camp where she conducted her undergraduate honors thesis studying the socialization of youth with type-1 diabetes. After graduating from college, she worked as a diabetes therapy associate at Medtronic helping patients gain access to insulin pump therapy. During medical school, she pursued her clinical interests in pediatric gastroenterology and endocrinology through clerkships in pediatric gastroenterology, pediatric endocrinology, and pediatric surgery at Rady Children's Hospital in San Diego as well as in pediatric endocrinology at Children's Hospital of Orange County. For her graduating thesis in medical school, she authored a literature review on the extra-intestinal manifestations of inflammatory bowel disease in children. She has joined Dr. Jacob's Laboratory to study the role of the microbiome in gastrointestinal as well as endocrine disorders.

Julianne Yang
Graduate Student

Julianne is a PhD student in the Molecular, Cellular, and Integrative Physiology Program who began her adventures in the Jacobs Lab in January 2020. She completed a BS in biochemistry and a minor in chemistry from the University of Illinois at Urbana-Champaign, where she wrote her undergraduate thesis on how autism and epilepsy-linked mutations in potassium ion channels regulate their trafficking and membrane expression in neurons. She is primarily interested in mechanisms by which the gut microbiome regulates neurological diseases, which can also then inform mechanisms of gut-brain communication in the healthy state. She is currently learning how to analyze 16S rRNA sequence data and plans to expand her data analysis repertoire to encompass other types of sequencing data as well. In her free time, she likes to zip around on a skateboard and spend time serving her cats.

Candace Chang
Graduate Student

Candace is a PhD student in the Molecular Toxicology Program under the joint mentorship of Dr. Jacobs and Dr. Jesus Araujo. In 2017, She completed her BS at UCLA in environmental science with a concentration in environmental health. She then volunteered at the UCI School of Medicine in the Air Pollution Health Effects Laboratory, where she participated in a cardiovascular project exploring the oxidative effects of particulate matter in ApoE -/- mice. This involved monitoring inhalation exposures and managing data from instruments such condensation particle counter and photometric ozone analyzer, as well as examining lungs for inflammatory cytokine expression and arteries for atherosclerotic plaque formation. Candace joined the Jacobs Laboratory to study the exciting, dynamic relationship that the gut microbiome has with the environment and its role in the etiology of IBD. Her dissertation project will encompass microbiome research of various mouse models to elucidate mechanisms by which inhaled ultra fine particles may cause intestinal inflammation.

Yi Zhou, MS
Visiting Graduate Researcher

Zhou is a senior PhD student majoring in preventive veterinary medicine at Sichuan Agricultural University, China. He works in the Jacobs Laboratory as a visiting graduate researcher through a two-year CSC (China Scholarship Council) scholarship. Zhou has been engaged in animal microecology research since starting his master's degree in 2013. For his PhD thesis project, he has investigated the effect of panda derived probiotics on the intestinal microbiome and immune system of pandanized mice (i.e. mice colonized with panda-derived microbiota) in the setting of DSS-induced colitis. Zhou has joined the Jacobs Laboratory to study the effects of Crohn's disease associated genetic variants on the intestinal microbiota and susceptibility to intestinal inflammation. This has provided him with the opportunity for additional training in gnotobiotic models and microbiome data analysis as he completes his PhD training.

Aaron Ahdoot
Undergraduate Student

Aaron is an undergraduate at UCLA pursuing a degree in biochemistry. Aaron's past research experience includes working at Biomerica, a biomedical company located in Irvine, CA. There he worked on a diagnostic project aimed at identifying foods in an individual's diet that can cause a heightened immune response and when removed, can alleviate symptoms of a number of digestive diseases including Irritable Bowel Syndrome. This research led him to join the Jacobs lab, where he has been involved in a study that aims to better characterize the brain-gut-microbiome axis and its role in gastrointestinal diseases. His other lab responsibilities include performing microbial DNA extraction and 16S ribosomal RNA sequencing of human and animal samples. After completing his undergraduate degree in Biochemistry, Aaron hopes to pursue an MD along with a PhD in medicinal chemistry.

Lucy Balish
Undergraduate Student

Lucy is originally from Portland, Oregon, and is currently studying psychobiology. She plans to attend medical school after graduating from UCLA. Prompted not only by her curiosity to learn more about the human microbiome and the effects it has on the digestive system, Lucy was also drawn to Dr. Jacob's Laboratory because of the wonderful people she knew were involved in it along with those she continued to meet within her first couple of weeks. Within the lab, she is helping investigate interactions between stress, the gut microbiome, and inflammatory bowel disease flares. Outside of the lab, she is involved with the American Lung Association at UCLA, a club she co-founded that works to improve lung health and prevent lung disease through advocacy and education. In her free time, Lucy enjoys hiking, running, traveling to new places, and spending time with friends and family.

Anil Chaganti
Undergraduate Student

Anil is from Simi Valley, California, 45 minutes north of UCLA. He joined the Jacobs Laboratory to gain experience in digestive diseases research and further understand the role of the gut microbiome in our bodies. After graduating, he plans to attend medical school to become a physician. During his free time, he likes to cook, hike, and eat at various restaurants with his family and friends.

Albert Duong
Undergraduate Student

Albert is a second year biology major from Sacramento, California. He joined the lab to gain experience with biomedical research and learn more about how our microbiome plays a role in our health. His long-term goal is to attend medical school and ultimately become either a primary care physician or a pathologist, depending on whether he decides on a primarily clinical or research focus for his career. Albert enjoys drawing, playing games, cooking, and going to church.

Grace Murphy
Undergraduate Student

Grace is a microbiology, immunology, and molecular genetics major with a minor in professional writing. She first became interested in the human gut microbiome during a physiological science course her freshman year. This initial interest led her to join the Jacobs Laboratory during her second year. Grace is specifically interested in the brain gut axis and how the gut microbiome impacts stress response. In addition to performing functions essential to the 16S sequencing pipeline, Grace helps maintain the gnotobiotic isolators for several germ-free studies. Outside of lab, Grace enjoys playing tennis and cooking.

Ryan Troutman
Undergraduate Student

Ryan is pursuing a BS in molecular, cell, and developmental biology and a minor in global health. Before joining the Jacobs Lab, Ryan worked as an advisor and coordinator for UCLA’s New Student and Transition Programs and volunteered as a Care Extender for UCLA Health. In the Jacobs Lab, Ryan is exploring how susceptibility for Parkinson’s disease and schizophrenia is influenced by the microbiome-gut-brain axis. His other lab responsibilities include performing behavioral assays, mouse handling, and genotyping mouse lines. After graduating from UCLA, Ryan hopes to pursue a master of nursing before practicing as a registered nurse. In his free time, Ryan enjoys grabbing coffee with friends, playing Dungeons and Dragons with his roommates, and exploring Los Angeles.

Jason Ye
Undergraduate Student

Jason is a second year UCLA undergraduate student from Warren, New Jersey, who is pursuing a degree in molecular, cellular, and developmental biology. He is particularly interested in cancer research and was inspired by his work on a clinical cancer drug trial at Bristol-Myers Squibb and as a research assistant at Sloan Kettering Cancer Center at the Tuomas Tammela Lab. As an undergraduate in the Jacobs Laboratory, he strives to contribute to ongoing microbiome research projects and to develop his capability in research in general. Jason plans to one day attend medical school and pursue a career in oncology. In his free time, Jason enjoys jogging, weightlifting, playing chess, and reading.