The role of microbial communities in the degradation of trace organic contaminants in the environment is little understood. In this study, the biotransformation potential of 27 pharmaceuticals and endocrine-disrupting compounds was examined in parallel with a characterization of the native microbial community in water samples from four sites variously impacted by urban run-off and wastewater discharge in Lake Mead, Nevada and Arizona, USA. Samples included relatively pristine Colorado River water at the upper end of the lake, nearly pure tertiary-treated municipal wastewater entering via the Las Vegas Wash, and waters of mixed influence (Las Vegas Bay and Boulder Basin), which represented a gradient of treated wastewater effluent impact. Microbial diversity analysis based on 16S rRNA gene censuses revealed the community at this site to be distinct from the less urban-impacted locations, although all sites were similar in overall diversity and richness. Similarly, Biolog EcoPlate assays demonstrated that the microbial community at Las Vegas Wash was the most metabolically versatile and active. Organic contaminants added as a mixture to laboratory microcosms were more rapidly and completely degraded in the most wastewater-impacted sites (Las Vegas Wash and Las Vegas Bay), with the majority exhibiting shorter half-lives than at the other sites or in a bacteriostatic control. Although the reasons for enhanced degradation capacity in the wastewater-impacted sites remain to be established, these data are consistent with the acclimatization of native microorganisms (either through changes in community structure or metabolic regulation) to effluent-derived trace contaminants. This study suggests that in urban, wastewater-impacted watersheds, prior exposure to organic contaminants fundamentally alters the structure and function of microbial communities, which in turn translates into greater potential for the natural attenuation of these compounds compared to more pristine sites.

微生物群落在环境中痕量有机污染物降解中的作用鲜为人知。在这项研究中，同时检查了27种药物和破坏内分泌的化合物的生物转化潜力，并同时表征了四个地点水样本中天然微生物群落的特征，这些地点受到米德湖，内华达州和亚利桑那州的城市径流和废水排放的不同影响， 美国。样品包括湖上端的相对原始的科罗拉多河水，通过拉斯维加斯洗车场进入的近纯的经过三次处理的市政废水，以及混合影响的水（拉斯维加斯湾和博尔德盆地），代表了经过处理的废水的梯度污水影响。基于16S rRNA基因普查的微生物多样性分析表明，尽管所有站点的总体多样性和丰富度都相似，但该站点的社区与受城市影响较小的站点不同。同样，Biolog EcoPlate分析表明，拉斯维加斯洗车场的微生物群落具有最强的代谢功能和活性。在大多数受废水影响最大的场所（拉斯维加斯洗车场和拉斯维加斯湾），有机污染物作为混合物添加到实验室缩微中，可以更快，更彻底地降解，并且大多数半衰期比其他场所或在抑菌对照中更短。 。尽管仍有待确定在受废水影响的地区提高降解能力的原因，这些数据与天然微生物适应环境（通过改变群落结构或代谢调控）适应废水中的痕量污染物有关。这项研究表明，在受废水影响的城市流域中，事先接触有机污染物会从根本上改变微生物群落的结构和功能，与更多原始的地区相比，这反过来转化为这些化合物自然衰减的潜力更大。