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

Cornelia Roder,Camille Daniels,Ernesto Weil,Chatchanit Arif,Christian R Voolstra

doi:10.1111/mec.12638

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.

Highlights

Corals are animals that live in a symbiotic relationship with photosynthetic dinoflagellates of the genus Symbiodinium as well as a rich bacterial community among other microorganisms that are collectively referred to as Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-2-x0nguqxi7yvz4966 C
Of the 59 222 microbial operational taxonomic units (OTUs) assayed on the PhyloChipTM G3 microarray, 11 256 OTUs were present in the coral samples collected from the Caribbean
OTU numbers were similar for both species (Orbicella faveolata and O. franksi) with more than a 50% increase in OTU richness in diseased corals compared with healthy specimens (Table 1)

Summary

Introduction

Corals are animals that live in a symbiotic relationship with photosynthetic dinoflagellates of the genus Symbiodinium as well as a rich bacterial community among other microorganisms that are collectively referred to as Konstanzer Online-Publikations-System (KOPS) URL: http://nbn-resolving.de/urn:nbn:de:bsz:352-2-x0nguqxi7yvz4966 C. While the causative agents remain unknown for most diseases (Rosenberg & Kushmaro 2011), it has been shown that compromised health in corals is accompanied by shifts in the microbial community associated with the coral holobiont (Sunagawa et al 2009; Kimes et al 2010; Cardenas et al 2012; Croquer et al 2012; Roder et al 2014) It is unclear whether infection of a single pathogen or opportunistic infections secondary to exposure to physiological stress trigger the restructuring of microbial communities in coral disease (Lesser et al 2007). PhyloChipTM 16S rRNA gene microarrays provide a standardized platform and have been successfully used to uncover microbial community patterns in coral disease (Sunagawa et al 2009; Kellogg et al 2012; Roder et al 2014)

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