The School of Neuroscience Graduate Program is proud to announce that Dawson Kropp has successfully defended his dissertation, Microbial and Immune Signatures of Stress and Antidepressants Across Sex and Generations.

The gut, brain, and immune system form an integrated and dynamic network that shapes development and health outcomes across the lifespan. Increasing evidence indicates that this axis is highly sensitive to stress exposure, displays robust sex-dependent properties, and may transmit biological effects across generations.

This dissertation investigated how variable stress or perinatal antidepressant exposure alters gut microbial composition, immune signaling, and behavioral phenotypes in a sex-specific and multigenerational manner. To address these questions, 16S rRNA or whole-genome shotgun metagenomic sequencing was utilized in tandem with behavioral assays and multiplex cytokine profiling in rat and mouse models of chronic stress or perinatal SSRI exposure.

Across studies, the gut microbiome exhibited innate sex differences that were present early in life and continued to diversify with age. Aging was associated with increased alpha diversity, marked shifts in microbial metabolic pathway representation, and a reversal of the Firmicutes–Bacteroidota ratio. Chronic stress induced distinct microbial alterations in males and females, with males showing a greater magnitude and diversity of microbial alterations. Female offspring more closely mirrored the microbial community structure of their dams, and perinatal citalopram treatment produced stronger and more persistent effects in female offspring than in males.

These findings reveal that stress and antidepressant exposure interact with sex and developmental stage to shape gut microbial composition and immune function. Microbial alterations following stress appear context-dependent, serving either compensatory or maladaptive roles depending on biological state and environmental challenge. Collectively, this work advances understanding of how the gut–brain–immune axis integrates life experience across sex and generations and highlights the microbiome as a dynamic mediator and potential therapeutic target in stress-related neuropsychiatric vulnerability.

Congrats Dr. Kropp!