title: Effect of oxidative stress induced by Brevibacterium sp. BS01 on a HAB causing species--Alexandrium tamarense.
abstract: Harmful algal blooms occur all over the world, destroying aquatic ecosystems and threatening other organisms. The culture supernatant of the marine algicidal actinomycete BS01 was able to lysis dinoﬂagellate Alexandrium tamarense ATGD98-006. Physiological and biochemical responses to oxidative stress in A. tamarense were investigated to elucidate the mechanism involved in BS01 inhibition of algal growth. Transmission electron microscope analysis revealed that there were some chloroplast abnormalities in response to BS01 supernatant. The decrease in cellular-soluble protein content suggested that cell growth was greatly inhibited at high concentration of BS01 supernatant. The increase in the levels of reactive oxygen species (ROS) and malondialdehyde contents following exposure to BS01 supernatant indicated that algal cells suffered from oxidative damage. The content of pigment was significantly decreased after 12 h treatment, which indicated that the accumulation of ROS destroyed pigment synthesis. Moreover, the decrease of Fv/Fm ratio suggested that in the photosynthetic system, the dominant sites producing ROS were destroyed by the supernatant of the BS01 culture. The activities of the antioxidant enzymes including superoxide dismutase and peroxidase increased in a short time and decreased slightly with increasing exposure time. A real-time PCR assay showed changes in the transcript abundances of two photosynthetic genes, psbA and psbD. The results showed that BS01 supernatant reduced the expression of the psbA gene after 2 h exposure, but the expression of the psbD gene was increased at concentrations of 1.0 and 1.5%. Our results demonstrated that the expression of the psbA gene was inhibited by the BS01 supernatant, which might block the electron transport chain, significantly enhancing ROS level and excess activity of the antioxidant system. The accumulation of ROS destoryed pigment synthesis and membrane integrity, and inhibited or ultimately killed the algal cells.
authors.affiliation: State Key Laboratory of Marine Environmental Science and Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystems, School of Life Sciences, Xiamen University, Xiamen, China.
authors.forename: Huajun
authors.initials: H
authors.lastname: Zhang
authors.forename: Xinli
authors.initials: X
authors.lastname: An
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Zhou
authors.forename: Bangzhou
authors.initials: B
authors.lastname: Zhang
authors.forename: Su
authors.initials: S
authors.lastname: Zhang
authors.forename: Dong
authors.initials: D
authors.lastname: Li
authors.forename: Zhangran
authors.initials: Z
authors.lastname: Chen
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
authors.forename: Shijie
authors.initials: S
authors.lastname: Bai
authors.forename: Jinglin
authors.initials: J
authors.lastname: Lv
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
authors.forename: Yun
authors.initials: Y
authors.lastname: Tian
authors.forename: Tianling
authors.initials: T
authors.lastname: Zheng
mesh_terms: D001951:Brevibacterium / Q000737:chemistry*; D002457:Cell Extracts / Q000032:analysis / Q000633:toxicity*; D049109:Cell Proliferation / Q000187:drug effects; D002736:Chloroplasts / Q000187:drug effects / Q000648:ultrastructure; D004141:Dinoflagellida / Q000187:drug effects / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects; D057097:Harmful Algal Bloom / Q000187:drug effects / Q000502:physiology*; D008315:Malondialdehyde / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D002457:Cell Extracts; D045332:Photosystem II Protein Complex; D017382:Reactive Oxygen Species; C422369:photosystem II, psbA subunit; D008315:Malondialdehyde