Bacterial profiling of White Plague Disease across corals and oceans indicates a conserved and distinct disease microbiome

Abstract

Coral diseases are characterized by microbial community shifts in coral mucus and tissue, but causes and consequences of these changes are vaguely understood due to the complexity and dynamics of coral-associated bacteria. We used 16S rRNA gene microarrays to assay differences in bacterial assemblages of healthy and diseased colonies displaying White Plague Disease (WPD) signs from two closely related Caribbean coral species, Orbicella faveolata and Orbicella franksi. Analysis of differentially abundant operational taxonomic units (OTUs) revealed strong differences between healthy and diseased specimens, but not between coral species. A subsequent comparison to data from two Indo-Pacific coral species (Pavona duerdeni and Porites lutea) revealed distinct microbial community patterns associated with ocean basin, coral species and health state. Coral species were clearly separated by site, but also, the relatedness of the underlying bacterial community structures resembled the phylogenetic relationship of the coral hosts. In diseased samples, bacterial richness increased and putatively opportunistic bacteria were consistently more abundant highlighting the role of opportunistic conditions in structuring microbial community patterns during disease. Our comparative analysis shows that it is possible to derive conserved bacterial footprints of diseased coral holobionts that might help in identifying key bacterial species related to the underlying etiopathology. Furthermore, our data demonstrate that similar-appearing disease phenotypes produce microbial community patterns that are consistent over coral species and oceans, irrespective of the putative underlying pathogen. Consequently, profiling coral diseases by microbial community structure over multiple coral species might allow the development of a comparative disease framework that can inform on cause and relatedness of coral diseases.

Keywords: 16S rRNA gene microarray; Orbicella faveolata; Orbicella franksi; Pavona duerdeni; Porites lutea; White Plague Disease (WPD); White Plague-like Disease; White Syndrome (WS); coral disease; microbial community.

Figure 1

Similarities between coral species, health state and ocean basin based on microbial communities. Multidimensional scaling (MDS) plot derived from Bray–Curtis distances of normalized PhyloChip™ HybScores (n = 7200 OTUs). Healthy (open) and WPD-affected (filled) specimens of the corals P. duerderni (square), Porites lutea (circle), Orbicella faveolata (triangle) and Orbicella franksi (diamond) are shown. Stress represents the goodness of fit of the data onto the MD ordination.

Figure 2

Bacterial footprints of WPD. Displayed are bacterial families and OTUs that showed a >2-fold abundance difference between HH and DD over samples from Pavona duerdeni (white), Porites lutea (light grey), Orbicella faveolata (black) and Orbicella franksi (dark grey). FC, fold change.

Figure 3

Grouping of corals based on underlying bacterial community structures. Relationship between healthy coral species in regard to differences in their bacterial community based on Euclidean distance of bacterial abundance (i.e. HybScores) from 7200 shared OTUs (1000 bootstraps). The dendrogram recaptures the phylogenetic relationship of the corals Orbicella franksi, Orbicella faveolata, Pavona duerdeni and Porites lutea.