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A fundamental question of host-microbiome co-evolution is how microbes specialize to ecological niches within hosts. For example, host-specific bacterial lineages within the vertebrate gut exhibit traits such as adherence, nutrient acquisition, and compatibility with host tissues and the mucosal immune system. Immunoglobulin A (IgA) is the dominant secretory immunoglobulin in the gut and has been shown to modulate the composition and function of the microbiome; however, the ecological impact of IgA on specific commensal bacterial lineages remains poorly understood. Limosilactobacillus reuteri are model gut symbionts whose adaptations to the vertebrate gastrointestinal tract have been established through genetic and functional approaches. Forestomach biofilm formation is a host-specific adaptation conserved within rodent-specific lineages of L. reuteri and biofilm formation correlates with the induction of specific IgA. In this thesis, a review of recent literature summarizes interactions between IgA and vertebrate gut microbes with relevant insights applied to ecological models in gnotobiotic mice colonized with L. reuteri. Experiments were performed to determine factors contributing to observed strain differences in host IgA production and investigate the consequence of adaptive immunity on biofilm production and ecological fitness of a vertebrate gut symbiont.
Advisor: Amanda Ramer-Tait