金属离子胁迫对Sphingomonas sp. Y2降解壬基酚聚氧乙烯醚特性的影响

壬基酚聚氧乙烯醚（NEPOs）是全球应用量最大的非离子型表面活性剂之一，具有环境雌激素毒性。NPEOs的中间代谢产物种类多、难降解，且毒性远高于其母系化合物。为研究金属离子对功能微生物Sphingomonas sp. Y2降解NPEOs特性的影响，分析了金属离子的最低抑制浓度（MIC）、细菌形态、NPEOs降解效率及代谢产物组成等变化。结果显示，菌株Y2对多种金属离子具有耐受性，在重金属培养基中对Mn²⁺、Zn²⁺具有较高的耐受性，MIC分别为500、90 mg/L；在500 mg/L Mn²⁺胁迫下，菌株Y2对NPEOs降解率为100.00%（3 d）；在90 mg/L Zn²⁺胁迫下，菌株Y2对NPEOs的降解率为20.62%（5 d）；两种离子双重胁迫下NPEOs降解率为15.65%（5 d）；Mn²⁺胁迫下菌株Y2细胞表面结构和形态发生明显变化，且改变了NPEOs代谢产物中组分的含量组成，其中短链NPEOs与短链壬基酚聚氧乙烯酸（NPECs）的比例为0.68，与对照相比，抑制/减缓了短链NPEOs的羧化反应。结果表明，菌株Sphingomonas sp. Y2对多种金属离子具有耐受性，Mn²⁺胁迫对细胞表面超微结构及NPEOs中间代谢产物组分组成产生显著影响。该研究将为表面活性剂类污染物的生物降解及相应代谢产物在环境中的毒性评价提供理论依据。

Effects of Metal Ion Coercion on Biodegradation of Nonylphenol Polyoxyethylene by Sphingomonas sp. Y2

Nonylphenol polyoxyethylene (NPEOs) is one of the most widely used non-ionic surfactants across the world, with environmental estrogen toxicity. Its intermediate metabolites of NPEOs are numerous in variety, difficult to degrade, and more toxic than its parent compounds. In order to study the effects of metallic ions on functional bacterium Sphingomonas sp. Y2 to degrade the feature of NPEOs, the experiments analyzed the minimum inhibitory concentration (MIC) of metallic ions, bacterial morph, degradation rate of NPEOs, and the change of metabolites composition. The results showed that Sphingomonas sp. Y2 possessed certain tolerance to a variety of metal ions, among heavy metals it had high tolerance to Mn²⁺ and Zn²⁺ in the TMM medium with MICs at 500 and 90 mg/L, respectively. Under the coercion of 500 mg/L Mn²⁺, Y2 had 100.00% NPEOs degradation rate in 3 d; and under the coercion of 90 mg/L Zn²⁺, Y2 and 20.62% NPEOs degradation rate in 5 d; in double coercion two ions the NPEOs degradation rate was 15.65% (5 d); The cell surface structure and morph of Y2 were significantly changed under Mn²⁺ stress, and changed the contents of metabolite components of NPEOs. Among them the ratio of short-chain NPEOs to short-chain nonylphenoxy carboxylates (NPECs) was 0.68, as compared with control one Mn²⁺ inhibited/slowed down the carboxylation reactions of NPEOs. The results showed that Y2 had tolerance to multiple metal ions, and Mn²⁺ coercion significantly affected ultrastructure of cell surface and the intermediate metabolites composition of NPEOs. The study will provide a theoretical foundation for the biodegradation of surfactant class pollutants and toxicity assessment of the corresponding metabolites in environment.