Pseudomonas fluorescens HYK0210-SK09 offers species-specific biological control of winter algal blooms caused by freshwater diatom Stephanodiscus hantzschii

Abstract

The study of an algicidal activity and mechanism of the isolated Pseudomonas fluorescens HYK0210-SK09 (SK09) was against a winter bloomed harmful diatom, Stephanodiscus hantzschii.SK09 was isolated from the Paldang reservoir, Korea and used to biological control of Stephanodiscus hantzschii. The inoculation of SK09 at the final density of 5 x 106 cells ml-1 caused degradation of >90% of S. hantzschii cells within 5 d. The algal cell lysis was achieved by a direct attack of the bacteria to the diatom cells, and the algicidal compound was located in the cytoplasm of the cell. Since SK09 did not suppress Microcystis aeruginosa, Anabaena cylindrica, Coelastrum astroideum, or Cyclotella meneghiniana, it appeared to attack S. hantzschii in a species-specific manner. Testing in an indoor mesocosms confirmed that SK09 effectively reduced S. hantzschii cells by 88% within 9 d. This bacterium is useful in regulating blooms of S. hantzschii. However, it should be studied in the future that their impact in shaping phytoplankton community and their activity in natural environments. The bacterium enabled us to develop a new strategy to understand the interaction for anthropogenic control of harmful algal blooms in nature.