Studies on Interspecies Interactions driven by Microbial Invasion that Shape the Stability and Function of Plant Associated Microbiomes

Abstract

Despite increasing recognition of the importance of plant microbiomes in agricultural systems, the mechanisms through which microbial invasions and interspecies interactions influence microbiome stability and functional outputs remain poorly understood. This dissertation investigates how microbial invasions, pathogen suppression, and interbacterial interactions shape microbial community dynamics and functions in plant.Chapters 2–4 collectively examine how microbial invasion, pathogen suppression, and interbacterial interactions contribute to microbiome stability and function. Chapters 2 and 3 focus on pathogen invasion and subsequent suppression, demonstrating how targeted antimicrobial strategies can not only reduce pathogen titre but also influence microbiome structure and recovery in plant-associated systems. In contrast, Chapter 4 shifts to a controlled synthetic community to dissect how interbacterial interactions drive functional outcomes, independent of pathogen presence. Chapter 2 evaluates the efficacy of a host-derived chimeric antimicrobial peptide (UGK17) in suppressing Candidatus Liberibacter asiaticus, while assessing its impact on the citrus phyllosphere microbiome. This chapter suggests that targeted antimicrobial strategies can control plant pathogens while minimizing unintended disruption of beneficial microbiota. Chapter 3 further investigates the ecological consequences of pathogen suppression in the field by examining the elimination of Xylella fastidiosa in grapevine leaves using the chimeric antimicrobial peptide UGK17. This chapter highlights that selective pathogen suppression can facilitate microbiome restoration. Chapter 4 explores how microbial interactions influence functional outputs within microbial communities using a synthetic bacterial community composed of xylanase producing bacteria. This chapter suggests that interbacterial interactions shift in response to neighboring species and that community complexity can contribute to more stable functional outcomes. Together, these studies provide new insights into how microbial invasions and interspecies interactions shape microbiome stability and function. Understanding these processes will facilitate the development of microbiome-based strategies to improve plant health, enhance crop productivity, and promote resilient agricultural ecosystems.