Effects of Zn(II) on metabolic activity of aerobic denitrifier Acinetobacter sp. JR-142

Abstract:

[Objective] To study the effects of different concentrations of Zn(II) on the metabolic activities, especially the denitrification of the aerobic denitrifier Acinetobacter sp. JR-142.[Methods] An aerobic denitrifier was screened out and its growth conditions were optimized. The growth curve, denitrifying efficiency, and cell morphology of the strain were measured in the presence of Zn(II) at different concentrations. We measured the activities of cell characteristic enzymes (nitrate reductase and nitrite reductase) exposed to different concentrations of Zn(II), and then analyzed the relationship between napA & nirS expression levels and enzyme activities.[Results] An aerobic denitrifying strain was obtained and identified as Acinetobacter sp. JR-142. Under the conditions of sodium succinate as carbon source, C/N ratio of 6, pH 7.0, temperature at 30℃, shaking speed of 180 r/min, the aerobic denitrifier showed the highest activity. Zn(II) at the concentration of 3.25 mg/L promoted the cell growth and aerobic denitrification, while that at the concentration higher than 52 mg/L showed inhibitory effects. The nitrate reductase and nitrite reductase activities in the control group and JR+0.05 treatment group were higher than those in the JR+0.8 treatment group. At the time point of 24 h, the relative expression levels of aerobic denitrifying genes napA and nirS in JR+0.05 treatment group were significantly higher than those in control group, which further indicated that 3.25 mg/L Zn(II) can promote aerobic denitrification. At the time points of 24 h and 32 h, the relative expression levels of the two genes in the control group and JR+0.05 treatment group were much higher than those in the JR+0.8 treatment group, which indicated that 52 mg/L Zn(II) can inhibit the reaction.[Conclusion] This study systematically analyzed the effects of Zn(II) at different concentrations on the growth and aerobic denitrification of Acinetobacter sp. JR-142 for the first time. It provides a data basis for the biological treatment of wastewater with nitrate-heavy metal combined pollution.

Key words:aerobic denitrification;Acinetobacter sp.;Zn(II) tolerance;metabolic activity;nitrate-heavy metal combined pollution