Phage-bacteria network analysis and its implication for the understanding of coral disease.

Multiple studies have explored microbial shifts in diseased or stressed corals; however, little is known about bacteriophage interactions with microbes in this context. This study characterized microbial 16S rRNA amplicons and phage metagenomes associated with Montastraea annularis corals during a concurrent white plague disease outbreak and bleaching event. Phage consortia differed between bleached and diseased tissues. Phages in the family Inoviridae were elevated in diseased or healthy tissues compared with bleached portions of diseased tissues. Microbial communities also differed between diseased and bleached corals. Bacteria in the orders Rhodobacterales and Campylobacterales were increased while Kiloniellales was decreased in diseased compared with other tissues. A network of phage-bacteria interactions was constructed of all phage strains and 11 bacterial genera that differed across health states. Phage-bacteria interactions varied in specificity: phages interacted with one to eight bacterial hosts while bacteria interacted with up to 59 phages. Six phages were identified that interacted exclusively with Rhodobacterales and Campylobacterales. These results suggest that phages have a role in controlling stress-associated bacteria, and that networks can be utilized to select potential phages for mitigating detrimental bacterial growth in phage therapy applications.