抗生素和重金属镉单一和复合污染对集胞藻PCC6803的影响

Effects of single and combined pollution of antibiotics and cadmium on growth of Synechocystis sp.PCC6803

为评估抗生素和重金属对藻类生态系统的影响,本研究探讨了四环素(tetracycline,TC)/磺胺甲噁唑(sulfamethoxazole,SMX)与Cd^(2+)的4个单一处理(100 ng/L TC;100 ng/L SMX;0.001 mg/L Cd^(2+);0.5 mg/L Cd^(2+))以及4个复合处理(100 ng/L TC+0.001 mg/L Cd^(2+);100 ng/L TC+0.5 mg/L Cd^(2+);100 ng/L SMX+0.001 mg/L Cd^(2+);100 ng/L SMX+0.5 mg/L Cd^(2+))对集胞藻的生长、光合活性以及抗氧化系统的影响。结果显示,100 ng/L SMX刺激集胞藻的生长和光合活性,而用100 ng/L TC处理则无明显影响;0.001 mg/L Cd^(2+)对集胞藻的各项指标均无明显影响,但0.5 mg/L Cd^(2+)明显抑制集胞藻的生长和光合作用,破坏抗氧化系统,损伤细胞膜,刺激集胞藻分泌胞外多糖。抗生素与镉复合污染处理方面,100 ng/L TC与0.001 mg/L Cd^(2+)共存时,增强集胞藻酯酶活性、刺激分泌胞外多糖;100 ng/L SMX与0.001 mg/L Cd^(2+)共存时,促进集胞藻生长、增强光合作用和酯酶活性;100 ng/L SMX与0.5 mg/L Cd^(2+)共存时,SMX能缓解高浓度Cd^(2+)造成的氧化损伤,较单一高浓度Cd^(2+)处理组的ROS产量减少、SOD酶活降低、MDA含量降低、协同刺激集胞藻酯酶活性;而100 ng/L TC不能显著缓解高浓度Cd^(2+)对细胞的损伤。研究结果表明,低浓度四环素对细胞生长影响较小,也基本不改变Cd^(2+)对集胞藻细胞的毒性,而低浓度磺胺甲噁唑会促进细胞生长,且能够减轻Cd^(2+)对集胞藻细胞的毒性,在污染评估时需综合考虑抗生素和重金属的复合污染。

Antibiotics and heavy metals are persistent pollutants in the environment,and the assessment of their toxicity to organisms has always been a hotspot of study.This article investigated the effects of single and combined pollution of tetracycline/sulfamethoxazole and cadmium ions on the growth of Syn⁃echocystis sp.PCC6803.The results showed that a single exposure to 100 ng/L sulfamethoxazole(SMX)stimulated the growth and photosynthetic activity of Synechocystis,whereas treatment with tetracycline(TC)had no significant effect.Cadmium ions(Cd^(2+))at 0.001 mg/L did not significantly affect the physiology of Synechocystis,but Cd^(2+)at 0.5 mg/L significantly inhibited the growth and photosynthesis of Syn⁃echocystis.This concentration downregulated photosynthesis-related gene(psbA2),disrupted the antioxidant system of Synechocystis,damaged its cell membranes,and stimulated the secretion of its extracellular polysaccharides.When 100 ng/L TC coexisted with 0.001 mg/L Cd^(2+)synergistically,the cellular esterase activity was stimulated.100 ng/L SMX alleviated oxidative damage caused by 0.5 mg/L Cd^(2+),resulting in the reduced production of reactive oxygen species(ROS),the decreased activity of superoxide dismutase(SOD),and the low content of malonaldehyde(MDA)compared to the group treated by single 0.5 mg/L Cd^(2+).When both were present simultaneously,they synergistically stimulated the activity of esterase in Synechocystis.Low concentrations of tetracycline had minimal impact on cell growth and did not significantly alter the cytotoxicity of Cd^(2+)on cells.In contrast,low concentrations of sulfamethoxazole promoted cell growth and mitigated the cytotoxic effects of Cd^(2+)on cells.It is indicated that it is necessary to comprehensively consider the combined pollution of antibiotics and heavy metals when pollution is assessed.