Phage-problem organism dynamics in biological wastewater treatment

点击翻译按钮获取中文摘要

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.