Microbiome Manipulation of Acropora cervicornis to Promote Resilience to the Parasite Aquarickettsia

Healthy coral microbiomes aid in nutrient cycling and immunological functions, but stress induced by shifts in environmental parameters can cause changes in the structure of these microbial communities. Microbiomes of the threatened scleractinian coral, Acropora cervicornis, are often dominated by Aquarickettsia rohweri, a parasitic microbe known to increase disease susceptibility in their hosts. The objectives of this study were to remove A. rohweri from the microbiomes of A. cervicornis, and subsequently introduce beneficial microbes of coral (BMCs) to promote a more resilient microbiome. Potentially beneficial microbes were isolated, characterized, and combined into BMC cocktails. Fragments of A. cervicornis of 2 genotypes with differing disease resistance were bleached utilizing temperature shock or menthol to remove existing microbial communities, and were subsequently fed coral food inoculated with BMC cocktails during the first week of the experiment. Coral microbiome samples were obtained pre inoculation, and 1 day 7 days, and 30 days post inoculation. Microbial 16S sequences were obtained from these samples and analyzed for alpha and beta diversity, and relative and differential abundance. Both bleaching treatments reduced populations of A. rohweri, and increased the diversity of A. cervicornis microbiomes. Different bleaching treatments were observed to be more effective with different genotypes. However, the corals did not incorporate microbes from the BMCs into their microbiomes. This study demonstrated the possibility of inducing shifts in coral microbiomes to remove harmful microbes and promote disease resilience. Different vectors for BMC inoculation at different coral life stages may aid in successfully transferring desired BMCs to hosts.

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jjkuhn@eckerd.edu