混合抗生素对铜绿微囊藻的生物效应

选取SP(螺旋霉素)和AM(阿莫西林)为目标化合物,研究二者的混合物对铜绿微囊藻的生长、Chla(叶绿素a)合成及微囊藻毒素合成与释放的影响. 结果表明:SP与AM以等毒性〔ρ(SP)∶ρ(AM)为1∶7,ρ(SP+AM)为4~15 μg/L〕混合时,铜绿微囊藻的生长及Chla的合成均受到抑制,并且ρ(SP+AM)越高,抑制作用越明显,在ρ(SP+AM)为15 μg/L时生长抑制率最大,为109.86%；SP与AM以等浓度〔ρ(SP)∶ρ(AM)为1∶1,ρ(SP+AM)为1~10 μg/L〕混合,ρ(SP+AM)≤4 μg/L时促进铜绿微囊藻的生长,ρ(SP+AM)为1 μg/L时促进作用最明显,铜绿微囊藻的比生长率高出对照组39.13%；ρ(SP+AM)≥5 μg/L时则抑制铜绿微囊藻生长；而Chla的合成在各试验浓度下均受到抑制. SP与AM对铜绿微囊藻的联合毒性表现为拮抗作用. 混合抗生素在各试验浓度和混合配比条件下,均导致藻细胞内藻毒素合成量的上升,并引起胞外藻毒素的释放量增加,ρ(SP)∶ρ(AM)为1∶7且ρ(SP+AM)为5 μg/L组释放比例最高,达到37.96%. 因此,混合抗生素的存在可导致铜绿微囊藻对水环境的危害进一步加深. 

Study on the Biological Effects of Mixed Antibiotics on Microcystis aeruginosa

Spiramycin (SP) and amoxicillin (AM) were selected as target antibiotics. The influences of binary mixtures of the two target antibiotics on algal growth, synthesis of Chla, production and release of target microcystins (MCs), MC-LR, MC-RR and MC-YR in Microcystis aeruginosa were investigated. When SP and AM were mixed according to the ratio of their EC₅₀ values (ρ(SP)∶ρ(AM)=1∶7), the algal growth rate and the amount of Chla decreased negatively correlated with the test concentrations after seven-day exposure to 4-15 μg/L of mixed antibiotics. The highest inhibition percentage of 109.86% was observed when treated with a mixture concentration of 15 μg/L. When SP and AM were mixed at equivalent ratio (ρ(SP)∶ρ(AM)=1∶1), the algal growth was stimulated at low concentrations of mixed antibiotics (ρ(SP+AM)≤4 μg/L). The highest growth rate was observed at mixture concentration of 1 μg/L, which was 39.13% higher compared with the control group. However, the algal growth was inhibited at the higher test concentrations (ρ(SP+AM)≥5 μg/L). The synthesis of Chla was inhibited at all test concentrations and all mixed ratios. The mixture of SP and AM showed antagonistic interaction. Furthermore, the mixed antibiotics induced an increase of production and release of target MCs. The highest proportion of extracellular MCs, up to 37.96%, was observed in 5 μg/L of mixed antibiotic-treated group at ratio of ρ(SP)∶ρ(AM)=1∶7. Therefore, the existence of mixed antibiotics would lead to increasing threats of M. aeruginosa to the aquatic environment.