Identification and control of a novel Escherichia coli phage in industrial production

Abstract:

[Background] Phages are viruses obligately lysing bacteria. They have a significant impact on the industrial fermentation of Escherichia coli. It is necessary to seek highly effective control measures to reduce the damage caused by phages to production. [Objective] To isolate an E. coli phage strain from the contaminated fermentation broth and analyze its biological characteristics and genome sequence. [Methods] A phage strain was isolated from the contaminated liquid of an amino acid production enterprise, and its morphology and structure was observed by transmission electron microscopy. The host range, temperature tolerance, pH tolerance, optimal multiplicity of infection, and one-step growth curve were determined for this phage strain. Furthermore, whole genome sequencing was performed for this strain. Finally, a bacterial defense system was selected to control this strain. [Results] A virulent E. coli phage strain was isolated and named JNP1. It can form clear and translucent plaques. The phage consisted of an icosahedral head approximately 60 nm in diameter and a long slender tail about 170 nm in length. JNP1 can tolerate the conditions of 4-50 ℃ and pH 5.0-10.0. It showcased the optimal multiplicity of infection of 0.1, the latent period of 10 min, the lysis period of 10-70 min, and the burst size of 110 PFU/cell. The full-length genome of the phage was 40 865 bp, with the G+C content of 44% and a total of 65 open reading frames. The phylogenetic analysis showed that this strain was a novel E. coli phage. Based on the biological and genomic characteristics of JNP1, the control effect of DNA phosphorothioation on this phage was evaluated. [Conclusion] In this study, a phage strain JNP1 was successfully isolated from the fermentation environment of E. coli in production. An industrial strain with the DNA phosphorothioation system can defense against this phage. This achievement provides a solid theoretical basis for formulating prevention and control strategies against phage contamination during industrial production.