THE EFFECTS OF SIMULATED MICROGRAVITY ON MICROCYSTIS AERUGINOSA DEPENDING ON THE NUTRIENT CONCENTRATIONS OF MEDIUM

In order to determine the interaction between nutrient concentration and simulated microgravity(SMG),Microcystis aeruginosa,cultured under rich and low nutrient medium(BG-11 and 1/10 BG-11 medium),were treated with different gravity conditions.Both of M.aeruginosa in BG-11 and 1/10 BG-11 were sensitive to SMG.Their growth and metabolism changed significantly after 2day-treatments.The effects of SMG varied significantly with the nutrient concentrations of medium.For M.aeruginosa cultured in BG-11,SMG led to the decreased cell number and photochemical efficiency of PS II as well as the increased cellular concentrations of chlorophyll a,carotenoid,phycocyanin,soluble protein and microcystin.The SMG induced changes of cells in 1/10 BG-11 were contrary to the above-mentioned changes of cells in BG-11.In1/10 BG-11,SMG led to the increased cell number and photochemical efficiency of PS II as well as the decreased cellular concentrations of chlorophyll a,carotenoid,phycocyanin,soluble protein and micro-cystin.The effects of SMG and nutrient limitation were alike when they were applied to M.aeruginosa separately.The influences of nutrient limitation were stronger than those of SMG.Under SMG,maybe the nutrient demand of cells was reduced,as a result of the suppressed growth and photochemical activity.Otherwise,SMG might enable cells to use nutriments more effectively.Thus,SMG could alleviate the stress of low nutrient medium to M.aeruginosa.Collectively,these findings supported that the nutrient concentration of medium could significantly affect the responses of M.aeruginosa to SMG.