Effects of Sb(V) on Growth and Chlorophyll Fluorescence of Microcystis aeruginosa (FACHB-905)

Microcystis aeruginosa was considered as one of the most common bloom-forming cyanobacteria. It often served as an ideal material for studying the effects of contamination on photosynthesis for the similarity with the chloroplast of higher plants.

Recent years, due to the application of Antimony (Sb) in various industries, high levels of Sb were detected in soil and water around smelters, industrial, and mining areas. Because Sb has potentially toxicity at very low concentrations, Sb pollution has become a growing environmental concern. Previous study has reported that photosystem II (PSII) activities of Synechocystis sp. were inhibited by Sb(III). But the knowledge of effects of Sb(V) on the PSII of cyanobacteria is still unclear.

To investigate the effects of Sb(V) on growth, pigments content, oxygen evolution, and PSII activity of M. aeruginosa, WANG Shuzhi and Prof. PAN Xiangliang from XIEG detected PSII activity of M. aeruginosa by the chlorophyll α (chl α) fluorescence measurement. In this study, JIP-test, QA^- reoxidation kinetic test and S-state test were used to study the energy distribution and electron transport in PSII.

The results showed that the treatment with Sb(V) at various concentrations ranging from 5 to 100 mg/l had long-term effects on growth, pigments content, and oxygen evolution of M. aeruginosa. Low concentration of Sb(V) had no significant inhibition of the biomass production and PSII activity but inhibited the pigment synthesis. Growth, pigments content, oxygen evolution, and PSII activity were seriously inhibited when treated by high concentration of Sb(V) (100 mg/l). The target sites of Sb(V) toxic effect on the PSII of M. aeruginosa were mainly on the donor side and the apparatus in the lightdependent reaction. The quantum yield for photochemistry, density of reaction centers and photosynthesis performance index decreased, whereas the dissipated energy increased. PSII activity of M. aeruginosa was promoted when exposure to 50 mg/l Sb(V) by increasing the density of active reaction centers and electron transport after QA^-.

This work was supported by Program of 100 Distinguished Young Scientists of the Chinese Academy of Sciences and National Natural Science Foundation of China (U1120302). The result was published in Current Microbiology on December 2012, 65(6): 733-741.