供水系统中的蓝细菌被认为是一个新的威胁,当一些物种产生有毒代谢物时,氰毒素,其中最广泛和研究最充分的是微囊藻毒素。饮用受污染的水是一种常见的氰毒素暴露途径,使研究饮用水中的蓝藻成为保护公众健康的优先事项。在饮用水处理厂,氯化化合物的预氧化被广泛用于抑制蓝细菌的生长,尽管存在对其降低氰基毒素含量的功效的担忧。此外,氯化对丰富但研究较少的氰基代谢物(例如毒性尚不清楚的氰基吡啶)的影响仍未得到充分研究。这里,两种氯化氧化剂,次氯酸钠(NaClO)和二氧化氯(ClO2),对有毒的蓝细菌铜绿微囊藻进行了测试,评估它们对细胞活力的影响,毒素概况和含量。内外微囊藻毒素和其他氰基代谢物,包括它们的降解产物,使用非靶向LC-HRMS方法进行鉴定。两种氧化剂都能够在低剂量(0.5mgL-1)时灭活铜绿分枝杆菌细胞,并大大降低细胞内毒素含量(>90%),无论治疗时间(1-3小时)。相反,NaClO处理后,细胞外毒素增加了两倍,表明细胞损伤。根据LC-HRMSn(n=2,3)证据,鉴定了一种新的代谢产物,命名为氰基吡啶型肽-1029,两种氧化剂对它的影响不同。NaClO导致其细胞外浓度从2增加到80-100μgL-1,ClO2诱导其氧化衍生物的形成,氰洞素型肽-1045。总之,对被有毒蓝细菌污染的原水进行预氧化处理可能导致饮用水中氰基毒素浓度增加,取决于化学剂,其剂量和治疗持续时间,也是氧化代谢物。由于这些代谢物对人类健康的影响仍然未知,参与饮用水管理的水安全机构应极其谨慎地处理这一问题。
Cyanobacteria in water supplies are considered an emerging threat, as some species produce toxic metabolites, cyanotoxins, of which the most widespread and well-studied are microcystins. Consumption of contaminated water is a common exposure route to cyanotoxins, making the study of cyanobacteria in drinking waters a priority to protect public health. In drinking water treatment plants, pre-oxidation with chlorinated compounds is widely employed to inhibit cyanobacterial growth, although concerns on its efficacy in reducing cyanotoxin content exists. Additionally, the effects of chlorination on abundant but less-studied cyanometabolites (e.g. cyanopeptolins whose toxicity is still unclear) remain poorly investigated. Here, two chlorinated oxidants, sodium hypochlorite (NaClO) and chlorine dioxide (ClO2), were tested on the toxic cyanobacterium Microcystis aeruginosa, evaluating their effect on cell viability, toxin profile and content. Intra- and extracellular microcystins and other cyanometabolites, including their degradation products, were identified using an untargeted LC-HRMS approach. Both oxidants were able to inactivate M. aeruginosa cells at a low dose (0.5 mg L-1), and greatly reduced intracellular toxins content (>90%), regardless of the treatment time (1-3 h). Conversely, a two-fold increase of extracellular toxins after NaClO treatment emerged, suggesting a cellular damage. A novel metabolite named cyanopeptolin-type peptide-1029, was identified based on LC-HRMSn (n = 2, 3) evidence, and it was differently affected by the two oxidants. NaClO led to increase its extracellular concentration from 2 to 80-100 μg L-1, and ClO2 induced the formation of its oxidized derivative, cyanopeptolin-type peptide-1045. In conclusion, pre-oxidation treatments of raw water contaminated by toxic cyanobacteria may lead to increased cyanotoxin concentrations in drinking water and, depending on the chemical agent, its dose and treatment duration, also of oxidized metabolites. Since the effects of such metabolites on human health remain unknown, this issue should be handled with extreme caution by water security agencies involved in drinking water management.