Context. Phages are viruses that infect bacteria and, by predation, can influence the bacterial population dynamics and, consequently, the function of a microbial community. This mechanism can compromise the efficiency of engineered systems that rely on the activity of a bacterial consortium, such as biological wastewater treatment (BWT).
Gap. Limited knowledge on the identity of phages in BWT processes, especially phages infecting functional bacterial, and their impact on treatment performance.
Aim. Isolate phages that infect key bacteria in wastewater treatment, and use them as a microbial ecology tool to study the function of the respective host in the microbial community.
Methods. First, phages were recovered from wastewater samples collected at different points of full-scale systems, adapting existing protocols to activated sludge samples and slow-growing bacterial hosts. Isolation of specific phages was performed by plaque assay, using known key organisms in nutrient removal that are available as pure cultures.
Findings. The adapted protocol for recovery, purification, and isolation of phages from wastewater was successfully applied. Samples were collected at different points of wastewater treatment processes, and a decrease in the number of phages along the process was observed. Multiple phages infecting Dechloromonas sp. were isolated from different WWTP. All isolated phages caused lytic infections, i.e. induce the lysis of the bacterial host, as shown by the formation of clear plaques in plate cultures. Further characterization of the isolated phages is being performed, and we envisage their application in mixed cultures to selectively infect the host.
Utilization. The isolation of phages infecting Dechloromonas sp. can be replicated for other bacterial hosts and applied to samples from different systems.
Increasing knowledge on the identity and activity of phages is necessary to understand the microbial ecology of BWT and can ultimately contribute to a more reliable monitoring, control and design of WWTP.
