Influence of a Bacteriophage on the Population Dynamics of Toxic Dinoflagellates by Lysis of Algicidal Bacteria

A lytic phage (empty setZCW1) was isolated from an algicidal bacterium Pseudoalteromonas sp. strain SP48 that specifically kills the toxic dinoflagellate Alexandrium tamarense. We demonstrated that oZCW1 could trigger the growth of A. tamarense by inhibiting the growth of algicidal bacterium SP48. In contrast, the growth of A. tamarense was suppressed when cocultured with either SP48 or the expty setZCW1-resistant mutant of SP48. This study provides the first evidence of the indirect impact of bacteriophage on bloom-forming microalgae via phage lysis of alga-killing bacteria.