We analyzed the impact of surfactant addition on hydrocarbon mineralization kinetics and the associated population shifts of hydrocarbon-degrading microorganisms in soil. A mixture of radiolabeled hexadecane and phenanthrene was added to batch soil vessels. Witconol SN70 (a nonionic, alcohol ethoxylate) was added in concentrations that bracketed the critical micelle concentration (CMC) in soil (CMC′) (determined to be 13 mg g−1). Addition of the surfactant at a concentration below the CMC′ (2 mg g−1) did not affect the mineralization rates of either hydrocarbon. However, when surfactant was added at a concentration approaching the CMC′ (10 mg g−1), hexadecane mineralization was delayed and phenanthrene mineralization was completely inhibited. Addition of surfactant at concentrations above the CMC′ (40 mg g−1) completely inhibited mineralization of both phenanthrene and hexadecane. Denaturing gradient gel electrophoresis of 16S rRNA gene segments showed that hydrocarbon amendment stimulated Rhodococcus and Nocardia populations that were displaced by Pseudomonas and Alcaligenes populations at elevated surfactant levels. Parallel cultivation studies revealed that the Rhodococcus population can utilize hexadecane and that the Pseudomonas and Alcaligenes populations can utilize both Witconol SN70 and hexadecane for growth. The results suggest that surfactant applications necessary to achieve the CMC alter the microbial populations responsible for hydrocarbon mineralization.
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机译：我们分析了表面活性剂添加对烃矿化动力学的影响以及土壤中降解烃的微生物的相关种群迁移。将放射性标记的十六烷和菲的混合物添加到分批土壤容器中。加入Witconol SN70（一种非离子型乙醇乙氧基化物），其浓度与土壤（CMC'）中的临界胶束浓度（CMC）包围在一起（确定为13 mg g -1 ）。以低于CMC'（2 mg g -1 ）的浓度添加表面活性剂不会影响任何一种烃的矿化速率。但是，当以接近CMC'的浓度（10 mg g -1 ）添加表面活性剂时，十六烷矿化被延迟，菲矿化被完全抑制。以高于CMC'（40 mg g -1 ）的浓度添加表面活性剂完全抑制了菲和十六烷的矿化。 16S rRNA基因片段的变性梯度凝胶电泳显示，碳氢化合物修饰刺激了假单胞菌和产碱菌种群在表面活性剂水平升高时取代的红球菌和诺卡氏菌种群。并行培养研究表明，红球菌种群可以利用十六烷，假单胞菌属和产碱菌种群可以利用维康醇SN70和十六烷来生长。结果表明，实现CMC所需的表面活性剂应用会改变负责烃矿化的微生物种群。
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