DNA Repair of UV-irradiated G. lamblia Cysts Following Low and Medium Pressure UV Disinfection

0302609 Shin 紫外线（UV）照射作为水处理过程中常规化学消毒剂的替代品最近获得了相当大的关注，因为最近发现其对高度耐氯的原生动物病原体（隐孢子虫卵囊和贾第鞭毛虫包囊）的显著灭活能力和相对低的产生有害消毒副产物（DBPs）的可能性。事实上，紫外线消毒是符合第2阶段消毒剂和消毒副产品规则（DBPR）和长期2强化地表水处理规则（LT2ESWTR）的最有前途的候选技术之一。尽管最近认识到紫外线消毒的前景，然而，仍然有几个问题，必须解决之前，广泛使用紫外线照射作为主要消毒剂，以实现微生物可接受的饮用水。其中一个问题是紫外线照射的水生病原体修复其紫外线损伤的DNA的能力。最近，我们的初步研究表明，G.当蓝氏虫包囊暴露于低剂量的低压紫外线并经受一定的修复条件时，它们可以恢复它们的感染性。因此，研究紫外线照射下G.蓝氏藻孢囊，然后确定该微生物的阈值UV剂量，以便将饮用水中该重要的水生微生物的水平降低到可接受的水平。因此，该活性的目的是确定紫外线照射的G.在暴露于低压和中压紫外线源后，通过动物和分子生物学测定确定所需剂量（阈值剂量）的紫外线照射，从而优化紫外线消毒过程，以使这种重要的水生微生物的可感知和可接受的水平。这一拟议的活动是一个罕见的研究DNA修复原生动物，可能是第一个研究，以表征使用各种分子生物学方法对这些微生物中的UV灭活和随后的修复的机制和动力学进行了研究。本研究所收集的信息将有助于我们阐明紫外线对银杏的损伤和修复现象的不同机制。在低压和中压UV暴露之后的Lamblia。此外，这些信息将有助于我们确定阈值紫外线剂量控制G。Lamblia孢囊的LP和MP UV技术，这将确保G.蓝氏藻孢囊，从而优化紫外线照射的有效剂量，以使这种重要的水生微生物达到保护公众健康的水平。关于每种类型紫外灯的主要紫外线损伤和修复机制的信息将使设计当前的处理设施和未来的紫外线技术以最大限度地灭活和修复对G.蓝氏囊藻和其他水生原生动物寄生虫的比较，也为水处理厂紫外灯的选型提供了另一个重要的依据。最后，本文介绍了与G.蓝氏虫包囊将很容易转移到未来的研究紫外线灭活和修复现象的机制，在其他新的和新兴的水生原生动物寄生虫。

0302609 Shin Ultraviolet (UV) irradiation has recently gained considerable attention as an alternative to conventional chemical disinfectants in water treatment processes after the recent discovery of its remarkable inactivation ability of the highly chlorine-resistant protozoan pathogens: Cryptosporidium parvum oocysts and Giardia lamblia cysts and relatively low potential of producing harmful disinfection byproducts (DBPs). In fact, UV disinfection is one of the most promising candidate technologies for compliance with the Stage 2 Disinfectants and Disinfection Byproduct Rule (DBPR) and Long Term 2 Enhanced Surface Water Treatment Rule (LT2ESWTR). Despite the recently recognized promise of UV disinfection, however, there are still several issues that must be addressed before widespread use of UV irradiation as a primary disinfectant to achieve microbially-acceptable drinking water. One such issue is the ability of UV-irradiated waterborne pathogens to repair their UV-damaged DNA. Recently, our preliminary study indicates that G. lamblia cysts can restore their infectivity when they were exposed to low doses of low pressure UV and subjected to certain repair conditions. It is important to characterize the extent and kinetics of DNA repair in UV-irradiated G. lamblia cysts and then identify the threshold UV dosage for this microorganism in order to reduce the level of this important waterborne microorganism in drinking water by an acceptable level. Therefore, the objective of this proposed activity is to determine the kinetics and the extent of the DNA repair capabilities of UV-irradiated G. lamblia cysts after exposure to from low and medium pressure UV sources with both animal and molecular biological assays order to identify required dosages (threshold dosages) of both UV irradiation and thereby optimize UV disinfection processes to inactivate this important waterborne microorganism by an appreciable and acceptable level.This proposed activity is one of the rare studies on DNA repair in protozoans and probably the first study to characterize the mechanism and kinetics of UV inactivation and subsequent repair in these microorganisms using various molecular biological methods. The information gathered in this proposed activity will enable us to elucidate the different mechanisms of UV damage and repair phenomenon in UV-irradiated G. lamblia after low and medium pressure UV exposure. Furthermore, this information will help us to determine the threshold UV dosages for control of G. lamblia cysts for both LP and MP UV technology which will ensure low or no DNA repair of G. lamblia cysts and thereby optimize the effective doses of UV irradiation to inactivate this important waterborne microorganism to levels that will protect public health. Information about the primary UV damage and repair mechanisms for each type of UV lamps would make it possible to design current treatment facilities and future UV technology for maximal inactivation and repair inhibition against G. lamblia cysts and other waterborne protozoan parasites, and also would provide another important selection criteria for UV lamp type in a water treatment plant by comparing their potential advantages. Finally, the information and experience gathered in this proposed activity with G. lamblia cysts will be easily transferred to future studies on mechanisms of UV inactivation and repair phenomena in other new and emerging waterborne protozoan parasites.