Collaborative Research: Sunlight Inactivation Mechanisms of Pathogenic Bacteria in Natural Waters

CBET 1334359/1335673 Alexandria Boehm/Kara NelsonStanford University/University of California Berkeley粪便指示细菌（FIB），如肠球菌和大肠杆菌，用于评估海滩水质，并作为人类病原体的替代物。天然沃茨中的FIB浓度随浓度的变化而变化，并且通常在下午三点左右低于测定检测限，而在晚上高出几个数量级，这具有几种含义。首先，样品收集的时间会极大地影响测量的浓度，这可能会导致水质标准的遵守和不遵守之间的差异。第二，目前尚不清楚实际病原体的浓度以及由此产生的相关健康风险是否也会经历这种波动。因此，获得有关控制FIB和相关人类病原体昼夜波动的过程的信息至关重要。日光被认为是FIB昼夜波动的主要原因。然而，阳光破坏微生物的主要机制还不清楚。至少有三种机制已被描述：内源性的直接损伤细胞成分的紫外线波长，和间接的内源性和外源性的光灭活所造成的反应物种产生的细胞内外，分别当光子被吸收的敏化剂分子。迄今为止的研究主要集中在FIB的光灭活，并已普遍高度经验和网站特定的，所以它是不可能概括预测在其他环境背景下或其他生物体的阳光灭活率。此外，关于细菌病原体的光灭活的数据显著缺乏。本项目的目的是表征FIB和一组病原菌对内源性和外源性光灭活的敏感性，并建立光灭活的定量模型。实验室实验将用于开发控制灭活过程的机械理解，并了解生物体之间观察到的差异的性质。现场和实验室数据将被纳入一个模型，以预测灭活率，该模型将使用微观研究进行测试。该模型将使用环境参数作为输入，以估计阳光对细菌的灭活，并将有助于估计各种生物和沃茨的灭活率，而无需进行特定地点和生物的研究。该研究将对FIB和细菌病原体在环境中的命运产生重要的见解，这是保护人类健康和改善沿海水质的高度优先研究需求。这项工作将对休闲用水的管理产生直接影响，以保护人类健康。对阳光介导的灭活机制的更好理解和新的建模方法也将直接用于工程和自然系统，其中阳光在消毒中起着重要作用，包括饮用水的太阳能消毒（SODIS）和池塘和湿地的废水处理。拟议工作的结果将与决策者和海滩管理人员分享，并将导致更好地保护人类健康。调查人员将把结果融入他们的课堂教学中。研究生和本科生将参与研究。调查人员将为高中生开发关于阳光对雨水径流处理影响的新课程，并为小学生开发一个关于水和环境工程的模块。

CBET 1334359/1335673Alexandria Boehm/Kara NelsonStanford University/University of California-BerkeleyFecal indicator bacteria (FIB), such as Enterococcus and Escherichia coli, are used to assess beach water quality and serve as proxies for human pathogens. FIB concentrations in natural waters vary diurnally with concentrations and are often below assay detection limits in mid-afternoon and orders of magnitude higher at night, which has several implications. First, the time the sample is collected dramatically impacts the measured concentration, which could make the difference between compliance and noncompliance with water quality standards. Second, it is not known whether the concentrations of actual pathogens, and thus associated health risk, also experience such fluctuations. Therefore, it is critical to obtain information on the processes that control the diurnal fluctuations for FIB and human pathogens of concern. Sunlight is believed to be the major cause of the diurnal fluctuations in FIB. However, the dominant mechanisms through which sunlight damages microorganisms are not well understood. At least three mechanisms have been described: endogenous direct damage to cellular components by ultraviolet wavelengths, and indirect endogenous and exogenous photoinactivation caused by reactive species generated inside and outside the cell, respectively, when photons are absorbed by sensitizer molecules. Research to date has primarily focused on FIB photoinactivation and has generally been highly empirical and site-specific so that it is not possible to generalize to predict sunlight inactivation rates in other environmental contexts or for other organisms. Additionally, there is a striking lack of data on the photoinactivation of bacterial pathogens. The objectives of this project are to characterize the susceptibility of FIB and a suite of pathogenic bacteria to endogenous and exogenous photoinactivation and develop a quantitative model for photoinactivation. Laboratory experiments will be used to develop a mechanistic understanding of processes that control inactivation, and to understand the nature of observed differences between organisms. Field and laboratory data will be incorporated into a model to predict inactivation rates, and the model will be tested using a microcosm study. The model will use environmental parameters as inputs to estimate the inactivation of bacteria by sunlight and will be useful for estimating inactivation rates for a wide range of organisms and waters without the need for site- and organism- specific studies.The project will advance knowledge in several ways. The research will yield essential insights into the fate of FIB and bacterial pathogens in the environment, a high priority research need to protect human health and improve coastal water quality. The work will have immediate implications for the management of recreational water for the protection of human health. The improved understanding of sunlight-mediated inactivation mechanisms and the new modeling approach will also be directly useful for engineered and natural systems in which sunlight plays a major role in disinfection, including solar disinfection of drinking water (SODIS) and wastewater treatment in ponds and wetlands. The results from the proposed work will be shared with policy makers and beach managers and will result in the improved protection of human health. The investigators will integrate the results into their classroom instruction. Graduate and undergraduate students will participate in the research. The investigators will develop new curriculum on the impact of sunlight on the treatment of stormwater runoff for high school students and a module on water and environmental engineering for elementary school students.