EFFECT OF ELEVATED BICARBONATE CONCENTRATION ON GROWTH, CHLOROPHYLL A FLUORESCENCE AND ULTRA-STRUCTURE OF Microcystis aeruginosa (CYANOBACTERIUM)

The influence of bicarbonate (HCO3-) on Microcystis aeruginosa FACHB 905 was assessed in this study. Growth curves, chlorophyll a fluorescence and ultrastructure were measured at two HCO3- concentrations, 2.3 mM and 12.4 mM. A treatment of sodium chloride (NaCl) was also conducted alongside to establish the influence level of sodium. It was found that upon treatment with elevated HCO3- concentrations of 2.3 mM and 12.4 mM, cell densities were 13% and 27% (respectively) higher than controls. In photosynthetic performance, elevated HCO3- concentration initially stimulated Fv/Fm at the prophase of culture and then subsequently inhibited it. The inhibition of 2.3mM was higher than that of 12.4mM HCO3-. The maximum relative electron transport rate (ETRmax) exhibited inhibition at elevated HCO3- concentrations. DI0/CS was decreased at 2.3 mM and increased at 12.4mM. In the case of both treatments. ABS/CSI TR0/CS, ET0/CS, RC/CS0 and RC/CSm were decreased by elevated HCO3- concentrations, which indicated damage to photosynthetic apparati and an inactivation of a fraction of reaction centers. This point was also proven by ultrastructural photos. High HCO3--exposed cells lost the characteristic photosynthetic membrane arrangement compared with the control and high salinity treated samples. At the 2.3mM concentration of HCO3-. damage to photosynthetic apparati caused decreased photosynthetic activity. These findings suggested that elevated HCO3- concentration stimulated the growth and photosynthesis of M. aeruginosa FACHB 905 in a short time. Exposure to high HCO3- concentrations for a longer period of time will damage photosynthetic apparatus. In addition, the ultrastructure indicated that elevated HCO3--concentration lead to photosynthetic apparati damage. In our experiment, it was observed that the inhibition effect of 2.3mM HCO3- was higher than that of 12.4mM HCO3-. We hypothesized that M. aeruginosa FACHB 905 induced a protective mechanism under high concentrations of HCO3-.

The influence of bicarbonate (HCO(3)(-)) on Microcystis aeruginosa FACHB 905 was assessed in this study. Growth curves, chlorophyll a fluorescence and ultrastructure were measured at two HCO(3)(-) concentrations, 2.3 mM and 12.4 mM. A treatment of sodium chloride (NaCl) was also conducted alongside to establish the influence level of sodium. It was found that upon treatment with elevated HCO(3)(-) concentrations of 2.3 mM and 12.4 mM, cell densities were 13% and 27% (respectively) higher than controls. In photosynthetic performance, elevated HCO(3)(-) concentration initially stimulated Fv/Fm at the prophase of culture and then subsequently inhibited it. The inhibition of 2.3mM was higher than that of 12.4mM HCO(3)(-). The maximum relative electron transport rate (ETRmax) exhibited inhibition at elevated HCO(3)(-) concentrations. DI(0)/CS was decreased at 2.3 mM and increased at 12.4mM. In the case of both treatments. ABS/CSI TR(0)/CS, ET(0)/CS, RC/CS(0) and RC/CS(m) were decreased by elevated HCO(3)(-) concentrations, which indicated damage to photosynthetic apparati and an inactivation of a fraction of reaction centers. This point was also proven by ultrastructural photos. High HCO(3)(-)-exposed cells lost the characteristic photosynthetic membrane arrangement compared with the control and high salinity treated samples. At the 2.3mM concentration of HCO(3)(-). damage to photosynthetic apparati caused decreased photosynthetic activity. These findings suggested that elevated HCO(3)(-) concentration stimulated the growth and photosynthesis of M. aeruginosa FACHB 905 in a short time. Exposure to high HCO(3)(-) concentrations for a longer period of time will damage photosynthetic apparatus. In addition, the ultrastructure indicated that elevated HCO(3)(-)-concentration lead to photosynthetic apparati damage. In our experiment, it was observed that the inhibition effect of 2.3mM HCO(3)(-) was higher than that of 12.4mM HCO(3)(-). We hypothesized that M. aeruginosa FACHB 905 induced a protective mechanism under high concentrations of HCO(3)(-).