LB 9-94 - CANCELLED - Do ecological distributions of microbial symbionts help identify probiotics?

Kelp are foundational macroalgal species with immense cultural, economic, and ecological value. Kelp cultivation is rapidly expanding to meet demands for sustainable food, fertilizer, and to support restoration of kelp habitat. Microbial symbionts influence many aspects of the biology of kelp and other macroalgae, including growth and development and environmental resilience. As a result, there is exploding interest in developing probiotics and other microbial manipulation strategies to improve host productivity, health, and resilience in sectors ranging from human health to aquaculture and agriculture to conservation. One of the major hurdles in microbiome manipulation for kelp and other species of economic importance is identifying the microbes most likely to impact the host trait of interest. This is in part because host-associated communities are complex, with 10s to 100s of symbionts that are acquired from the environment and vary across time and space. Understanding the ecological distribution of microbes on kelp in the wild may enable us to select probiotic candidates more efficiently. This is because microbes that are consistently associated with a host (core taxa) are hypothesized to have a greater effect on host biology (Core influence function hypothesis). Yet, many of the probiotics currently in use across sectors are common microbes that are easy to culture but are rarely found on the host in natural settings (any ole microbe; AOM). Within this framework, we 1) identified the core taxa of sugar kelp (Saccharina latissima) from wild populations in British Columbia, Canada, 2) assessed the influence of 129 bacterial strains isolated from sugar kelp on growth and development of sugar kelp gametophytes and juvenile sporophytes in the laboratory. Frequency in natural populations (a measure of core) is positively correlated with the ability of isolates to increase growth and development rates, measured by # of sporophytes produced after 4 weeks, in support of CIHF (core hypothesis). However, this is a trend and variability is high. Isolates that most strongly increase the # of sporophytes range in frequency on host populations from 2% to 95%. High growth with low-frequency isolates provides support for AOM and highlights the need for broader testing.