Effects of algicidal bacterium BS03 (Microbulbifer sp.) on the growth and antioxidant systems of Alexandrium tamarense
溶藻细菌BS03(Microbulbifer sp.)对塔玛亚历山大藻生长及抗氧化系统的影响

Objective]We studied the algicidal mechanism of extracellular substances of algicidal bacteria strain BS03(Microbulbifer sp.) on photosynthetic characteristics,antioxident enzyme system and cysteine-dependent aspartate specific protease-3(Caspase-3) of Alexandrium tamarense.Methods] We tested photosynthetic pigments,chlorophyll fluorescence efficiency,antioxidant systems and caspase-3 activity in the algae cells treated with 0.5%,1.0%,1.5% and 2.0% BS03 cell-free filtrate after 12,24,36 and 48 h.Results](1) The chlorophyll-a and chlorophyll fluorescence efficiency Fv/Fm decreased with the increase of BS03 cell-free filtrate and treatment time.Carotenoids contents of A.tamarense cells treated with low BS03(0.5% and 1.0%) cell-free filtrate were higher than the control.(2) Antioxident enzyme activities varied as treatment time and concentration.Malodialdehyde(MDA) contents increased significantly with BS03 cell-free filtrate treatment.(3) Caspase-3 protease activities of algal cells increased by BS03 cell-free filtrate.Conclusion] BS03 inhibited the photosynthesis whereas enhanced the lipid peroxidation of the cellular membrane of Alexandrium tamarense,indicating its algicidal activity.