Abstract
Corals are rapidly declining globally due to coral diseases. Skeletal growth anomalies (SGA) or “coral tumors” are a group of coral diseases that affect coral reefs worldwide, including Hong Kong waters in the Indo-Pacific region. To better understand how bacterial communities may vary in corals with SGA, for the first time, we examined the bacterial composition associated with the apparently healthy and the diseased tissues of SGA-affected Platgyra carnosus using 16S ribosomal rRNA gene pyrosequencing. Taxonomic analysis revealed Proteobacteria, Bacteroidetes, Cyanobacteria, and Actinobacteria as the main phyla in both the apparently healthy and the diseased tissues. A significant difference in the bacterial community composition was observed between the two conditions at the OTU level. Diseased tissues were associated with higher abundances of Acidobacteria and Gemmatimonadetes, and a lower abundance of Spirochaetes. Several OTUs belonging to Rhodobacteraceae, Rhizobiales, Gammaproteobacteria, and Cytophaga-Flavobacterium-Bacteroidetes (CFB) were strongly associated with the diseased tissues. These groups of bacteria may contain potential pathogens involved with the development of SGA or opportunistic secondary or tertiary colonizers that proliferated upon the health-compromised coral host. We suggest that these bacterial groups to be further studied based on inoculation experiments and testing of Koch's postulates in efforts to understand the etiology and progression of SGA.
Highlights
In the past two decades, coral reefs have been rapidly declining due to environmental impacts, such as infectious diseases (Harvell et al, 2007), bleaching (Baker et al, 2008), fishing overexploitation (Willis et al, 2004), predator outbreaks (Kayal et al, 2012), and global climate change (Hoegh-Guldberg et al, 2007)
We established that Skeletal growth anomalies (SGA) in P. carnosus produces significant differences in bacterial community composition between the apparently healthy and the diseased tissues at Operational Taxonomic Units (OTUs) level
We report differentially abundant members between the two conditions in Acidobacteria, Rhizobiales and Rhodospirillaceae
Summary
In the past two decades, coral reefs have been rapidly declining due to environmental impacts, such as infectious diseases (Harvell et al, 2007), bleaching (Baker et al, 2008), fishing overexploitation (Willis et al, 2004), predator outbreaks (Kayal et al, 2012), and global climate change (Hoegh-Guldberg et al, 2007). Skeletal growth anomalies (SGA) or “coral tumors” are a group of coral diseases affecting the major reefs of the IndoPacific (Chiu et al, 2012; Tavakoli-Kolour et al, 2015), Australia (Haapkylä et al, 2010), Hawaii (Stimson, 2011), Costa Rica (Gateño et al, 2003), and the Philippines (Kaczmarsky and Richardson, 2011). The etiology of SGA is unknown, studies have shown that the disease is linked to environmental factors, such as climate change (Rosenberg and Ben-Haim, 2002), sea surface temperature, and human population size (Aeby et al, 2011). The increase in sea surface temperature is often attributed for inducing physiological stress, which allows for transmission of pathogenic agents in compromised corals (Rosenberg and Ben-Haim, 2002)
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