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UBC Theses and Dissertations

Identification of core microbiome on macroalgal species, and microbial manipulation in commercial kelp culture Park, Jungsoo


There is a growing recognition of the important role that host-associated microbes play in the biology and health of seaweeds. The seaweed cultivation industry is rapidly expanding due to its high demand for various applications and as a nutritious food source. As a result, there is a growing interest in exploring the potential for manipulating the microbiome to improve seaweed aquaculture and identify potential probiotic strains more effectively. Recent studies have highlighted an increase in disease and a decline in crop yields in seaweed aquaculture, which can be attributed to intensified and global distribution. However, our current understanding of the influence of microbes on seaweed cultivation remains limited. The distribution of bacteria within the microbiome of seaweeds naturally varies both in space and time. The core microbiome hypothesis suggests that bacteria consistently present in the microbiome of hosts are more likely to play an important functional role. This makes the core bacteria an appealing target for microbial manipulation. In my research, I aim to test the core microbiome hypothesis, which suggests that the ecological distribution of bacteria can serve as a predictive factor for their influence on host biology. In Chapter 2, I developed a better understanding of the distribution of seaweed-associated bacteria and show how different ways of defining the core microbiome result in different suites of bacteria identified as the core, and conclude that sampling across broader spatial and temporal scales result in a more robust set of core bacteria. I found that most of these core bacteria from Fucus distichus were also widespread across seaweed species. In Chapter 3, I identified core bacteria associated with wild sugar kelp (Saccharina latissima) and their distribution on cultivated S. latissima. I then conducted experimental tests investigating the impact of microbial manipulation on S. latissima biology using bacterial isolates in the cultivation of S. latissima. The results revealed that bacteria can indeed alter growth and development of sugar kelp, and found a positive correlation between bacterial taxa found at high frequency on wild S. latissima and their effect on S. latissima development. Chapter 4 tested the prediction that the bacteria most commonly found on wild kelp (the core) would be more successful at colonizing kelp in laboratory cultures. Overall, my findings suggest that selecting probiotic strains from the core candidates could be a valuable strategy, as they are more likely to influence host biology and colonize kelp in a deterministic manner.

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