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Updated: Aug 10, 2025

Author Spotlight: An Adapted Optical Density-Based Microplate Assay for Characterizing Actinobacteriophage Infection
Published on: June 30, 2023
Microbial density-dependent viral dynamics and low activity of temperate phages in the activated sludge process
Ruyin Liu1, Zong Li2, Ganghua Han2
1College of Resources and Environment, University of Chinese Academy of Sciences, No.19(A) Yuquan Road, Shijingshan District, Beijing 100049, China; RCEES-IMCAS-UCAS Joint-Lab of Microbial Technology for Environmental Science, University of Chinese Academy of Sciences, Beijing, China; Yanshan Earth Critical Zone National Research Station, University of Chinese Academy of Sciences, Beijing, China; Binzhou Institute of Technology, Weiqiao-UCAS Science and Technology Park, Binzhou City, Shandong Province, China.
Abstract:
The ecological behavior of bacteriophages (phages), the most abundant biological entity in wastewater treatment systems, is poorly understood, especially that of temperate phages. Here, the temporal dynamics of lytic and temperate phages in a laboratory-scale activated sludge reactor with a sludge bulking issue was investigated using coupled sludge metagenomic and viromic analyses. The lysogenic fragments (prophages) identified were widely distributed in the reconstructed metagenome-assembled genomes (61.7%, n = 227). However, only 12.3% of the identified prophages experienced lysogenic-lytic switching, and the abundance contribution of prophages to free virus communities was only 0.02-0.3%, indicating low activity of temperate phages. Although the sludge community changed dramatically during reactor operation, no massive prophage induction events were detected. Statistical analyses showed strong correlations between sludge concentration and free virus and temperate phage communities, suggesting microbial density-dependent virus dynamics in the sludge microbiota.
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