ClO2杀灭拟柱孢藻过程中毒素释放行为与释放机理

试验考察了二氧化氯(ClO_2)杀灭拟柱孢藻过程中不同条件下柱孢藻毒素(CYN)随时间的释放规律,对释放量与时间数据进行曲线方程拟合,并以透射电镜观察不同反应时间拟柱孢藻细胞形态,对柱孢藻毒素的释放机理进行分析。结果表明,反应初期5 min内CYN释放率随时间延长快速提高,随后增长缓慢,30 min后趋于稳定。ClO_2投加量影响了CYN释放速率,1.0 mg/L ClO_2投加量时CYN释放率要高于0.5 mg/L和0.7 mg/L时,但在反应2 h后不同ClO_2投加量的CYN释放率趋于接近。拟柱孢藻初始浓度对CYN释放率的影响不明显。CYN释放率在酸性条件下高于中性和碱性条件。随反应温度升高,CYN释放率逐渐升高。各种反应条件下CYN释放量与反应时间的关系可以用曲线方程来表示。藻细胞形态随反应时间延长发生变化。ClO_2投加量增大,藻细胞结构的破坏程度加剧。在反应初期CYN释放是通过扩散作用而并非由细胞壁的破裂而致。     

Allelopathic effect of Cylindrospermopsis raciborskii extracts on the germination and growth of several plant species

Cylindrospermopsis raciborskii is an invasive cyanobacterium and a potential producer of the alkaloid toxin cylindrospermopsin (CYN). Extracts of two strains of C. raciborskii were tested for their effects on the germination and growth of Lactuca sativa, Phaseolus vulgaris, Pisum sativum and Solanum lycopersicum. Germination was not significantly inhibited for any of the plant species tested, but growth was affected, depending on the species. Root and stem growth in L. sativa was generally stimulated by both strains. Ph. vulgaris root growth was stimulated by both strains but no effect was visible in stem growth. S. lycopersicum root growth was inhibited by both strains and stem growth was inhibited only by the CYN strain. P. sativum root growth was also inhibited by both strains but stem growth was stimulated. CYN accumulation was also differential with toxin transfer to the stem. Ph. vulgaris accumulated the highest CYN concentration. This study suggests that plants behave differently in their response to this toxin and that roots and stems also show different abilities to react and accumulate the toxin. Knowledge of the impact of CYN- and non-CYN-producing cyanobacteria in different plant species and translocation of the toxin to different plant parts is essential for the avoidance of human as well as environmental health hazards.     

Tumor promoting effects of cyanobacterial extracts are potentiated by anthropogenic contaminants--evidence from in vitro study

Inhibition of gap junctional intercellular communication (GJIC) is affiliated with tumor promotion process and it has been employed as an in vitro biomarker for evaluation of tumor promoting effects of chemicals. In the present study we investigated combined effects of anthropogenic environmental contaminants 2,2′,4,4′,5,5′-hexachlorobiphenyl (PCB 153) and fluoranthene, cyanotoxins microcystin-LR and cylindrospermopsin, and extracts of laboratory cultures of cyanobacteria Aphanizomenon gracile and Cylindrospermopsis raciborskii, on GJIC in the rat liver epithelial cell line WB-F344. Binary mixtures of PCB 153 with fluoranthene and the mixtures of the two cyanobacterial strains elicited simple additive effects on GJIC after 30 min exposure, whereas microcystin-LR and cylindrospermopsin neither inhibited GJIC nor altered effects of PCB 153 or fluoranthene. However, synergistic effects were observed in the cells exposed to binary mixtures of anthropogenic contaminants (PCB 153 or fluoranthene) and cyanobacterial extracts. The synergistic effects were especially pronounced after prolonged (6-24 h) co-exposure to fluoranthene and A. gracile extract, when mixture caused nearly complete GJIC inhibition, while none of the individual components caused any downregulation of GJIC at the same concentration and exposure time. The effects of cyanobacterial extracts were independent of microcystin-LR or cylindrospermopsin, which were not detected in cyanobacterial biomass. It provides further evidence on the presence of unknown tumor promoting metabolites in cyanobacteria. Clear potentiation of the GJIC inhibition observed in the mixtures of two anthropogenic contaminants and cyanobacteria highlight the importance of combined toxic effects of chemicals in complex environmental mixtures.