Fall 2025 FDSC Graduate Seminar

10:05 AM

Unnikrishnan Kannan (George lab)

Differential effects of foodborne nanoplastics in inflammatory bowel disease (IBD) and non-IBD conditions 

Global plastic production continues to rise, and persistent polymers gradually break down into microplastics and nanoplastics (NPs) that contaminate food and are subsequently ingested. However, it remains unclear how gastrointestinal (GI) transformation influences the bioactivity of these particles and whether this contributes to the progression of intestinal diseases. This study hypothesizes that foodborne NPs exacerbate inflammation and compromise intestinal barrier function in individuals predisposed to inflammatory bowel disease (IBD). To evaluate this, we will develop a comprehensive library of food contact NPs and characterize to establish their surface chemistry. GI transformation will be simulated using the standardized INFOGEST protocol, and pristine particles will be compared with digesta-conditioned counterparts in-vitro epithelial barrier models to quantify uptake pathways and cellular response. Interactions between NPs and the gut microbiome will be studied through in-vitro colonic fermentation to identify the taxonomic
alterations and release of plastic additives to the gut. Findings will be extended to human intestinal organoids derived from non-IBD and IBD donors to assess tissue-level outcomes including tight junction disruption, retention, and inflammation within an adverse outcome. This integrative approach aims to clarify how physicochemical transformation shapes epithelial stress, barrier integrity, and microbiome composition, thereby contributing to IBD pathogenesis. Further, these studies are expected to identify molecular and cellular mechanisms underpinning health risks of NPs and guide mitigation strategies to protect vulnerable populations, including recommendations for safer food contact materials and reductions in dietary exposure.

10:30 AM

Pierre-Luc Longchamps (Lu lab)

Induction of Campylobacter jejuni persister cells

Campylobacter jejuni is the most common cause of bacterial gastroenteritis in Canada, with its main sources being undercooked poultry, raw milk and contaminated water. C. jejuni is sensitive to various environmental stresses, making its recovery challenging despite the frequency of clinical cases. It is hypothesized that C. jejuni utilizes dormancy states such as the persister and VBNC state to tolerate environmental stresses and recover in favorable conditions. The persister state is a transient, non-growing phenotypic state with increased tolerance to various stresses, particularly antibiotic stress. Persisters may appear stochastically, but it has been found that various stresses, such oxidative stress, UV stress, starvation and others can increase the persister fraction in a population. While persisters cannot be directly observed or counted in a population, time-killing curves with antibiotics can be utilized to estimate the number of persisters. The slope of the biphasic killing curve produced during these assays is used to estimate the initial persister count. The first two chapters will explore how various stresses encountered in the food supply chain (real food matrices and simulated food processing environments) can affect the persister population in C. jejuni cultures. In the final chapters, modern technologies including microfluidics and various -omics tools (Raman spectroscopy, RNA sequencing, mass spectrometry, etc.,) will be utilized to identify key mechanisms in the dormancy continuum of C. jejuni. Various mechanisms such as toxin-antitoxin systems, SOS response, stringent response and (p)ppGpp will be tested to determine how they affect the formation of C. jejuni  persister cells;

11:00 AM

Joana López Gachuzo (Lu lab)

Inactivation of Campylobacter jejuni persisters in the agro-ecosystem using metal oxide nanoparticles

Campylobacter jejuni is a foodborne pathogen primarily found in the intestine of animals, with poultry serving as the main reservoir. It spreads through cross-contamination in slaughterhouses and the consumption of undercooked meat. Common symptoms of campylobacteriosis include diarrhea, vomiting, and abdominal cramps, but in severe cases, the infection can affect the nervous system and lead to Guillain-Barré syndrome. Due to its high prevalence in chicken meat, C. jejuni poses a significant health risk in both developed and developing countries. Controlling this pathogen remains challenging because of its ability to survive harsh environments at high concentrations. Part of the reason for this is that C. jejuni can enter a dormant state, forming persister cells that evade detection by conventional culture methods due to their reduced metabolic activity under environmental stress, such as antimicrobial exposure. Although these cells do not grow under unfavorable conditions, they can resume replication once conditions improve,
complicating efforts to eradicate the pathogen. Given these challenges, the objective of my thesis is to inactivate C. jejuni persisters, incorporating metal oxide nanoparticles, which generate reactive oxygen species (ROS), and damage cellular components by inducing stress.