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Abstract White band disease (WBD) has decimated the Caribbean staghorn coral, Acropora cervicornis, since its emergence in 1979, but its etiology remains unknown. Numerous WBD pathogen candidates from over nine bacterial families have been implicated, with a multi-year field study recently identifying Cysteiniphilum litorale as the likely pathogen. Here, we use 16S rRNA gene amplicon sequencing to profile changes in the bacterial communities in a tank-based transmission experiment in the Florida Keys using 50 nursery-raised staghorn coral genotypes with varying disease resistances to determine whether any bacteria in the native staghorn coral microbiomes were associated with WBD resistance and to identify bacterial amplicon sequencing variants (ASVs) associated with WBD exposure and transmission. We found no significant associations, positive or negative, between any bacterial ASV, genus, or family and disease resistance in native staghorn coral microbiomes but did identify nine bacterial ASVs strongly associated with disease outcome in the tank-based transmission experiment. ASV 65, classified as Cysteiniphilum litorale, showed strong disease associations consistent with pathogenicity, including being significantly associated with WBD transmission within disease-exposed tanks (i.e. more abundant on diseased fragments) and being significantly more abundant on the diseased experimental dose than the healthy dose. The V3-V4 16S rRNA gene sequence for ASV 65 differed by only 1 of 415 bp from the C. litorale ASV identified as the putative WBD pathogen in the recent multi-year study from Panama, suggesting a rare Caribbean-wide strain-level pathogen association. Eight additional disease-associated ASVs were identified as potential opportunistic pathogens and included ASVs from the families Vibrionaceae and Colwelliaceae.
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Geographically driven differences in microbiomes of Acropora cervicornis originating from different regions of Florida’s Coral Reef
Effective coral restoration must include comprehensive investigations of the targeted coral community that consider all aspects of the coral holobiont—the coral host, symbiotic algae, and microbiome. For example, the richness and composition of microorganisms associated with corals may be indicative of the corals’ health status and thus help guide restoration activities. Potential differences in microbiomes of restoration corals due to differences in host genetics, environmental condition, or geographic location, may then influence outplant success. The objective of the present study was to characterize and compare the microbiomes of apparently healthy Acropora cervicornis genotypes that were originally collected from environmentally distinct regions of Florida’s Coral Reef and sampled after residing within Mote Marine Laboratory’s in situ nursery near Looe Key, FL (USA) for multiple years. By using 16S rRNA high-throughput sequencing, we described the microbial communities of 74 A. cervicornis genotypes originating from the Lower Florida Keys ( n = 40 genotypes), the Middle Florida Keys ( n = 15 genotypes), and the Upper Florida Keys ( n = 19 genotypes). Our findings demonstrated that the bacterial communities of A. cervicornis originating from the Lower Keys were significantly different from the bacterial communities of those originating from the Upper and Middle Keys even after these corals were held within the same common garden nursery for an average of 3.4 years. However, the bacterial communities of corals originating in the Upper Keys were not significantly different from those in the Middle Keys. The majority of the genotypes, regardless of collection region, were dominated by Alphaproteobacteria, namely an obligate intracellular parasite of the genus Ca. Aquarickettsia . Genotypes from the Upper and Middle Keys also had high relative abundances of Spirochaeta bacteria. Several genotypes originating from both the Lower and Upper Keys had lower abundances of Aquarickettsia , resulting in significantly higher species richness and diversity. Low abundance of Aquarickettsia has been previously identified as a signature of disease resistance. While the low- Aquarickettsia corals from both the Upper and Lower Keys had high abundances of an unclassified Proteobacteria, the genotypes in the Upper Keys were also dominated by Spirochaeta . The results of this study suggest that the abundance of Aquarickettsia and Spirochaeta may play an important role in distinguishing bacterial communities among A. cervicornis populations and compositional differences of these bacterial communities may be driven by regional processes that are influenced by both the environmental history and genetic relatedness of the host. Additionally, the high microbial diversity of low- Aquarickettsia genotypes may provide resilience to their hosts, and these genotypes may be a potential resource for restoration practices and management.
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- PAR ID:
- 10347459
- Date Published:
- Journal Name:
- PeerJ
- Volume:
- 10
- ISSN:
- 2167-8359
- Page Range / eLocation ID:
- e13574
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.7717/peerj.13574
