Novel T4 bacteriophages associated with black band disease in corals

Research into causative agents underlying coral disease have focused primarily on bacteria, whereas potential roles of viruses have been largely unaddressed. Bacteriophages may contribute to diseases through the lysogenic introduction of virulence genes into bacteria, or prevent diseases through lysis of bacterial pathogens. To identify candidate phages that may influence the pathogenicity of black band disease (BBD), communities of bacteria (16S rRNA) and T4-bacteriophages (gp23) were simultaneously profiled with amplicon sequencing among BBD-lesions and healthy-coral-tissue of Montipora hispida, as well as seawater (study site: the central Great Barrier Reef). Bacterial community compositions were distinct among BBD-lesions, healthy coral tissue and seawater samples, as observed in previous studies. Surprisingly, however, viral beta diversities based on both operational taxonomic unit (OTU)-compositions and overall viral community compositions of assigned taxa did not differ statistically between the BBD-lesions and healthy coral tissue. Nonetheless, relative abundances of three bacteriophage OTUs, affiliated to Cyanophage PRSM6 and Prochlorococcus phages P-SSM2, were significantly higher in BBD-lesions than in healthy tissue. These OTUs associated with BBD samples suggest the presence of bacteriophages that infect members of the cyanobacteria-dominated BBD community, and thus have potential roles in BBD pathogenicity.