Abstract
A novel Podoviridae lytic phage AJO2, specifically infecting Acinetobacter johnsonii, was isolated from bulking activated sludge. The one-step growth experiment showed that the latent period and burst size of AJO2 were estimated to be 30 min and 78.1 phages per infected cell, respectively. The viability test indicated that neutral conditions (pH 6–8) were table for AJO2 survival, while it was sensitive to high temperature (≥60°C) and ultraviolet treatment (254 nm). Genomic sequencing revealed that the AJO2 had a linearly permuted, double-stranded (ds) DNA consisting of 38,124 bp, with the G+C content of 41 mol%. A total of 58 putative open reading frames (ORFs), 11 pairs of repeats and 11 promoters were identified. The AJO2 genome had a modular gene structure which shared some similarities to those of A. baumanii phages. However, genomic comparative analysis revealed many differences among them, and novel genes were identified in the AJO2 genome. These results contribute to subsequent researches on the interaction between bacteriophages and hosts in wastewater treatment, especially during the bulking period. Additionally, the newly isolated phage could be a good candidate as a therapeutic agent to control nosocomial infections caused by A. johnsonii.
Highlights
As a common problem in activated sludge systems, sludge bulking draws extensive attention worldwide because of its serious consequences, such as poor sludge settle ability, water quality deterioration, sludge loss, or even system failure (Wagner, 1982; Madoni et al, 2000; Martins et al, 2004)
This study describes the physiological characteristics and genome sequence of an A. johnsonii phage from bulking sludge
Bioinformatic analysis and comparison reveal that AJO2 is a novel lytic phage, with unique genomic features and relatively low similarity to other Acinetobacter phages
Summary
As a common problem in activated sludge systems, sludge bulking draws extensive attention worldwide because of its serious consequences, such as poor sludge settle ability, water quality deterioration, sludge loss, or even system failure (Wagner, 1982; Madoni et al, 2000; Martins et al, 2004). Phages appear to be active components of activated sludge systems and phage-mediated bacterial mortality has the potential to influence treatment performance by influencing the bacterial abundance (Withey et al, 2005). On the one hand, analyzing the dynamic changes of bacteriophages that infect key functional groups contributes to understanding the malfunctions in WWTPs. On the other hand, the host specificity of phages makes them a potentially efficient tool to eliminate bulking-related filamentous bacteria. The HHYphage lysing Haliscomenobacter hydrossis (Kotay et al, 2011), SNP-phage lysing Sphaerotilus natans (Kotay et al, 2010) and THE1 lysing Tetrasphaera jenkinsii (Petrovski et al, 2012) have been isolated from activated sludge with the goal of filamentous bulking control. It is urgent to isolate and genetically characterize more phages in activated sludge, especially during the bulking period The main reason is that only a few phages have been isolated and sequenced, limiting its characterization and further application of “phage therapy.” it is urgent to isolate and genetically characterize more phages in activated sludge, especially during the bulking period
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