Phage-problem organism dynamics in biological wastewater treatment

噬菌体或噬菌体是专性寄生虫，需要原核宿主的新陈代谢机制才能繁殖。它们在微生物群落的生态和进化中发挥着重要作用，影响着自然和工程系统中细菌的丰度和多样性、群落组成和功能。尽管人们知道噬菌体在海洋系统中的作用，但对它们如何影响废水处理的了解仍然很少。在生物废水处理(BWT)中，噬菌体丰富，而细菌是主要的处理剂，是它们的宿主。因此，噬菌体在BWT中发挥的作用，在它们对细菌联合体的影响方面，以及随后它们如何影响处理后的出水质量，正受到越来越多的关注。噬菌体活性可以促进系统内的生物量和生产力，但它也可能通过失去关键的功能生物体(例如，负责去除氨的氨和亚硝酸盐氧化细菌)而导致失败。事实上，阐明噬菌体在关键功能基团上的作用及其时间动力学和相互作用有助于预测过程性能和系统故障，并有助于将噬菌体用作生防剂。噬菌体裂解细菌宿主的能力为将其用作控制微生物群落动态的工具提供了机会，类似于传染病中的噬菌体疗法。BWT中存在着大量的问题微生物，例如，膨胀和起泡微生物的过度生长会阻碍二次澄清；反硝化菌不能将硝酸盐完全转化为氮气，会释放出一种强有力的温室气体--一氧化二氮；积累糖原的微生物(GAO)会与积累磷酸盐的微生物(PAO)竞争，导致强化生物除磷(EBPR)的恶化；亚硝酸氧化细菌(NOB)会抑制部分亚硝化-氨氧化(PNA)过程；或甚至在工艺废水中释放对三级处理具有抵抗力的病原体。因此，本博士学位旨在更好地了解BWT中的噬菌体，并评估它们在问题微生物的生物控制中的潜在应用。这项计划将涉及(I)发展独立于培养物的方法，以结合病毒标记和活的荧光活化细胞分类(FACS)来识别和分离活性污泥系统中的问题生物的病毒，(Ii)在全规模系统中对病毒-问题宿主对进行时间监测，(Iii)估计全规模系统中问题生物的捕食率，以及(Iv)进行培养和培养实验，以评估分离的噬菌体作为对问题生物的干预的有效性。

Bacteriophages, or phages, are obligate parasites that require the metabolic machinery of their prokaryotic hosts to reproduce. They play an essential role in the ecology and evolution of microbial communities, influencing bacterial abundance and diversity, community composition and function, both in natural and engineered systems. Despite knowledge of the role of phages in marine systems, an understanding of how they influence wastewater treatment is still lacking.Phages are abundant in biological wastewater treatment (BWT), and bacteria, the primary agents of treatment, are their hosts. Consequently, the role phages play in BWT, in terms of their impact on the bacterial consortia and, subsequently, how they can influence the quality of treated effluent, is receiving increased attention. Phage activity can promote biomass and productivity within a system, but it can also lead to failures through the loss of key functional organisms (e.g., ammonia and nitrite oxidising bacteria responsible for ammonia removal). Indeed, elucidating the role of phages on key functional groups and their temporal dynamics and interactions could help predict process performance and system failures and facilitate the potential use of phages as biocontrol agents.The ability of phage to lyse their bacterial hosts offers an opportunity for their use as tools to control microbial community dynamics, analogous to phage therapy in infectious diseases. Numerous problem organisms exist in BWT; for example, the overgrowth of bulking and foaming organisms can hinder secondary clarification; denitrifiers unable to perform the complete conversion of nitrate to nitrogen gas can release nitrous oxide, a potent greenhouse gas; glycogen-accumulating organisms (GAO) compete with phosphate-accumulating organisms (PAO) and can lead to the deterioration of the enhanced biological phosphorus removal (EBPR); nitrite oxidising bacteria (NOB) can supress partial nitritation-annamox (PNA) process; or even the release of pathogenic organisms resistant to tertiary treatment in process effluents.Therefore, this PhD aims to gain a greater understanding of bacteriophages in BWT and assess their potential use in the biocontrol of problem organisms. This project will involve (i) the development of culture-independent methods to identify and isolate viruses of problem organisms in activated sludge systems by combining viral tagging with live fluorescence-activated cell sorting (FACS), (ii) the temporal monitoring of virus-problem host pairs in full-scale systems, (iii) the estimation of predation rates of problem organisms from the full-scale systems and (iv) culturing and incubation experiments to assess the effectiveness of isolated bacteriophage as an intervention against problem organisms.