Phage Therapy of Coral White Plague Disease: Properties of Phage BA3

The bacteriophage BA3 multiplies in and lyses the coral pathogen Thalassomonas loyana. The complete genome of phage BA3 was sequenced; it contains 47 open reading frames with a 40.9% G + C content. Phage BA3 adsorbed to its starved host in seawater with a k = 1.0 × 10−6 phage ml−1 min−1. Phage therapy of coral disease in aquarium experiments was successful when the phage was added at the same time as the pathogen or 1 day later, but failed to protect the coral when added 2 days after bacterial infection. When the phages were added 1 day after coral infection, the phage titer increased about 100-fold and remained present in the aquarium water throughout the 37-day experiment. At the end of the experiment, the concentration of phages associated with the corals was 2.5 ± 0.5 × 104 per cm2 of coral surface. Corals that were infected with the pathogen and treated with phage did not transmit the disease to healthy corals.