Dissecting Impacts of Host-microbiome Interactions on Phytoplankton Microbiome Assembly
Yang, Jinny
2024
Abstract
Almost all eukaryotic organisms, from microscopic algae to humans, are host to closely associated communities of microorganisms, called microbiomes, that are important for host health. Host-microbiome interactions constitute a critical ecological process that impacts the functions of both the host and the microbial community, yet much remains to be learned about the nature, mechanisms, and impacts of these interactions. This dissertation aims to extend the current understanding of how host-microbiome interactions influence microbiome assembly by using phytoplankton as a model host system. It does so by dissecting the effects of innate host selection and host-microbiome feedback on phytoplankton microbiome assembly. Innate host selection implies that the microbiome is formed solely based on the phytoplankton-produced dissolved organic matter (DOM) composition as innately produced by the host in function of host species or physiological state. Conversely, host-microbiome feedback refers to how the microbiome's presence modifies host DOM production, thereby influencing ecological selection applied by the host on the microbiome. Throughout this dissertation, I utilized the freshwater microalga Chlorella sorokiniana and its associated microbiome as a model system. In Chapter 2, focusing on the overall microbiome impacts, I found that innate host selection and host- microbiome feedback led to divergent microbiome compositions while collectively maintaining microbiome richness. However, the host-microbiome feedback reduced microbiome evenness. These findings inspired the hypothesis that the two effects selected for different microbes: innate host selection favored passive symbionts thriving on host-derived DOM, whereas the host-microbiome feedback favored active symbionts capable of triggering direct host-microbe interactions to their advantage. To test this hypothesis, Chapter 3 identified two bacterial species from C. sorokiniana's microbiome that thrived better under different treatments: (i) solely innate host selection, representing passive symbionts, and (ii) in the presence of host-microbiome feedback, representing active symbionts. Further analysis of metabolic dynamics revealed that the active symbiont adjusted its metabolic status significantly between treatments, potentially synthesizing chemical signals to facilitate direct interactions with the host. Additionally, the host's gene expression profile indicated a higher expression of metabolic functions related to the biosynthesis of plant-microbe mutualistic interaction compounds (e.g., flavonoids) only when co-cultured with the active symbiont. In Chapter 4, expanding into environmental factors, I investigated how nutrient supply affects the impacts of innate host selection and host- microbiome feedback on microbiome assembly using a microbiome of seven phytoplankton- associated bacteria. The results showed divergent microbiome compositions between the two effects and among different nitrogen supplies. Particularly, the presence of host-microbiome feedback revealed a specific bacterium hindering host growth, resulting in only two bacterial species establishing the microbiome at the lowest nitrogen level. However, this antagonistic bacterium was suppressed by the host at the highest nitrogen level, allowing for a more diverse microbiome (six species). Overall, this dissertation demonstrated that microbiome assembly is shaped by both host selection and host-microbiome feedback, with the two effects selecting for different microbiomes that can be influenced by the external nitrogen supply levels.Deep Blue DOI
Subjects
Host-microbiome interactions
Types
Thesis
Metadata
Show full item recordCollections
Remediation of Harmful Language
The University of Michigan Library aims to describe library materials in a way that respects the people and communities who create, use, and are represented in our collections. Report harmful or offensive language in catalog records, finding aids, or elsewhere in our collections anonymously through our metadata feedback form. More information at Remediation of Harmful Language.
Accessibility
If you are unable to use this file in its current format, please select the Contact Us link and we can modify it to make it more accessible to you.