Microbiome differences in disease-resistant vs. susceptible Acropora corals subjected to disease challenge assays

Stephanie M Rosales,Dana E Williams,Xaymara M Serrano,Nikki Traylor-Knowles,Margaret W Miller,Benjamin Young

doi:10.1038/s41598-019-54855-y

Abstract

In recent decades coral gardening has become increasingly popular to restore degraded reef ecosystems. However, the growth and survivorship of nursery-reared outplanted corals are highly variable. Scientists are trying to identify genotypes that show signs of disease resistance and leverage these genotypes in restoring more resilient populations. In a previous study, a field disease grafting assay was conducted on nursery-reared Acropora cervicornis and Acropora palmata to quantify relative disease susceptibility. In this study, we further evaluate this field assay by investigating putative disease-causing agents and the microbiome of corals with disease-resistant phenotypes. We conducted 16S rRNA gene high-throughput sequencing on A. cervicornis and A. palmata that were grafted (inoculated) with a diseased A. cervicornis fragment. We found that independent of health state, A. cervicornis and A. palmata had distinct alpha and beta diversity patterns from one another and distinct dominant bacteria. In addition, despite different microbiome patterns between both inoculated coral species, the genus Sphingomonadaceae was significantly found in both diseased coral species. Additionally, a core bacteria member from the order Myxococcales was found at relatively higher abundances in corals with lower rates of disease development following grafting. In all, we identified Sphingomonadaceae as a putative coral pathogen and a bacterium from the order Myxococcales associated with corals that showed disease resistant phenotypes.

Highlights

In recent decades coral gardening has become increasingly popular to restore degraded reef ecosystems
192 and 225 amplicon sequence variants (ASVs) remained for A. cervicornis (N = 60) and A. palmata (N = 35), respectively
We evaluated the microbiomes of nursery-reared Caribbean Acropora corals that were tested for disease susceptibility[21]

Summary

Introduction

In recent decades coral gardening has become increasingly popular to restore degraded reef ecosystems. A field disease grafting assay was conducted on nursery-reared Acropora cervicornis and Acropora palmata to quantify relative disease susceptibility. There are varying levels of success rates in acroporid outplant because they are exposed to different environments[5], heat stress[6], and diseases[7]. The corals Acropora cervicornis and Acropora palmata were historically the dominant species in the Caribbean but are both critically endangered[8,9] Their populations have plummeted mostly due to disease outbreaks[10] and heat stress caused by global climate change[11]. Unaffected pathogen caused differences in disease susceptibility between Acropora millepora genotypes and a shift in the microbial community to a more pathogenic state[15]

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Conclusion