Coral Pathogens Identified for White Syndrome (WS) Epizootics in the Indo-Pacific

Abstract

BackgroundWhite Syndrome (WS), a general term for scleractinian coral diseases with acute signs of advancing tissue lesions often resulting in total colony mortality, has been reported from numerous locations throughout the Indo-Pacific, constituting a growing threat to coral reef ecosystems.Methodology/Principal FindingsBacterial isolates were obtained from corals displaying disease signs at three WS outbreak sites: Nikko Bay in the Republic of Palau, Nelly Bay in the central Great Barrier Reef (GBR) and Majuro Atoll in the Republic of the Marshall Islands, and used in laboratory-based infection trials to satisfy Henle-Koch's postulates, Evan's rules and Hill's criteria for establishing causality. Infected colonies produced similar signs to those observed in the field following exposure to bacterial concentrations of 1×106 cells ml−1. Phylogenetic 16S rRNA gene analysis demonstrated that all six pathogens identified in this study were members of the γ-Proteobacteria family Vibrionacae, each with greater than 98% sequence identity with the previously characterized coral bleaching pathogen Vibrio coralliilyticus. Screening for proteolytic activity of more than 150 coral derived bacterial isolates by a biochemical assay and specific primers for a Vibrio family zinc-metalloprotease demonstrated a significant association between the presence of isolates capable of proteolytic activity and observed disease signs.Conclusion/SignificanceThis is the first study to provide evidence for the involvement of a unique taxonomic group of bacterial pathogens in the aetiology of Indo-Pacific coral diseases affecting multiple coral species at multiple locations. Results from this study strongly suggest the need for further investigation of bacterial proteolytic enzymes as possible virulence factors involved in Vibrio associated acute coral infections.

A bacterial pathogen uses dimethylsulfoniopropionate as a cue to target heat-stressed corals

“…Control bottles containing only the basal media and DMSP were used to account for the possible chemical breakdown of DMSP. Results from these experiments were confirmed using an alternative V. coralliilyticus strain, LMG 23696 (Sussman et al, 2008). Bottles inoculated with the Pseudovibrio sp.…”

Bacterial diversity and White Plague Disease-associated community changes in the Caribbean coral Montastraea faveolata

“…Vibrio spp. have previously been reported to either cause or be associated with higher prevalence in a number of coral diseases (Kushmaro et al, 1996;Ben-Haim and Rosenberg, 2002;Cervino et al, 2004;Gil-Agudelo et al, 2006Sussman et al, 2008). Furthermore, Vibrio spp.…”

Genomic and proteomic analyses of the coral pathogen Vibrio coralliilyticus reveal a diverse virulence repertoire

“…The P1 genome had several phage genes that were not present in the LMG 20984T genome, indicating that phages may allow genome diversification within the species V. coralliilyticus. The VcpA zinc-metalloprotease has been identified in previous studies as the key virulence factor likely important in the bacterial infection of corals and implicated in coral tissue necrosis (Ben-Haim et al, 2003a, b;Sussman et al, 2008). The V. coralliilyticus vcpA gene is orthologous to the vtpA gene from the oyster pathogen Vibrio tubiashii and similarly identified as central for strain virulence (Hasegawa et al, 2008).…”

“…Investigations of white syndrome coral disease outbreaks in the Indo-Pacific between 2003 and 2006 isolated a number V. coralliilyticus strains from different coral species (Pachyseris speciosa, Montipora aequituberculata and Acropora cytherea) and identified them as the potential causative agents (Sussman et al, 2008). The extracellular products derived from the V. coralliilyticus strain P1 (LMG23696) isolated from diseased Montipora aequituberculata colonies in Nelly Bay (Great Barrier Reef), caused photoinactivation of the Symbiodiunium (zooxanthellae) endosymbiont (Sussman et al, 2008).…”

“…The extracellular products derived from the V. coralliilyticus strain P1 (LMG23696) isolated from diseased Montipora aequituberculata colonies in Nelly Bay (Great Barrier Reef), caused photoinactivation of the Symbiodiunium (zooxanthellae) endosymbiont (Sussman et al, 2008). Analysis of the extracellular products from strain P1 revealed a predominant zinc-metalloprotease that was found to be a homolog of the Vibrio cholerae hemagglutinin-protease (Sussman et al, 2008). When purified from the other extracellular products, this zinc-metalloprotease was demonstrated to cause coral tissue damage within 18 h at 27 1C (Sussman et al, 2009).…”