Publication Date
5-2024
Date of Final Oral Examination (Defense)
4-16-2024
Type of Culminating Activity
Dissertation
Degree Title
Doctor of Philosophy in Ecology, Evolution, and Behavior
Department Filter
Biology
Department
Biological Sciences
Supervisory Committee Chair
Leonora S. Bittleston, Ph.D.
Supervisory Committee Member
Sarah M. Gray, Ph.D.
Supervisory Committee Member
Marie-Anne de Graaff, Ph.D.
Supervisory Committee Member
Kevin Feris, Ph.D.
Abstract
Our research investigates the function and composition of microbial communities across various conditions, shedding light on microbial community dynamics and plant-microbe interactions. Despite the crucial role microbes play in Earth's ecosystems, many questions remain about how microbiomes function and their direct impact on host health.
The first chapter explores the links between bacterial community function and the growth of purple pitcher plants (Sarracenia purpurea). We introduced three distinct bacterial communities into sterile pitchers to assess their effects on plant health. Different bacterial functions influenced plant traits, with communities rich in decomposition and secondary metabolite production traits leading to significantly larger leaves compared to bacteria-free pitchers. Additionally, the bacterial community associated with larger pitchers exhibited increased expression of transcripts linked to microbially-produced plant hormones.
The second chapter examines how environmental factors shape microbial community function and composition. By subjecting a diverse microbial community to various abiotic conditions—varying pH, nutrient levels, and temperatures—we observed clear shifts in both bacterial community composition and function over time. Different abiotic conditions impacted microbial functions differently; for instance, temperature stress boosted chitinase activity while suppressing protease activity. We also noted shifts in microbial community composition based on interactions between temperature, pH, and nutrients.
In chapter three, we investigate how variations in arthropod detritus affect microbial-driven decomposition and community function. Using sterile mesh bags filled with different types of sterile arthropod prey, we assessed whether prey type influenced decomposition rates in pitcher plants. We found that prey with higher exoskeleton content, like ants and beetles, decomposed at a slower rate compared to prey with lower exoskeleton content, such as flies. Additionally, protease activity was highest in the fly treatment, indicating varied effects of different prey types on microbial function and composition.
Overall, we found that two major themes developed throughout this research. The first is, microbial community composition does not always predict community function. For example, in Chapter 1, the relative abundance of the top 20 taxa was very similar across functionally dissimilar communities. Additionally, in Chapter 2, we found that abiotic conditions influenced community function and composition differently. Lastly, in Chapter 3 we found that large shifts in the rates of insect decomposition resulted from relatively small changes in community structure, making it difficult to use composition to predict function. The second theme of this research can be summarized by saying, that microbial function matters. We found evidence overall that small differences in microbial community function were often driven by even smaller differences in composition, despite this, we found outsized effects of function on plant growth and prey decomposition. This further illustrates that community dynamics are complex, multiple measures of community composition and function should be integrated to better understand them. In conclusion, this research presents a culmination of experiments, observations, and analyses linking microbial communities to their environment and hosts. We find that the minute interactions between microbes in these communities can have widespread implications for ecosystem health. Microbial function is a critical, yet often overlooked, aspect of ecosystem dynamics. By recognizing the diverse influences of microbial function, we gain insights for more innovative approaches in research and conservation.
DOI
https://doi.org/10.18122/td.2149.boisestate
Recommended Citation
Bernardin, Jessica Rae, "The Functional Dynamics of Bacterial Communities in Relation to Environmental Selection and Host Health in a Pitcher Plant Model System" (2024). Boise State University Theses and Dissertations. 2149.
https://doi.org/10.18122/td.2149.boisestate
