Isolation and characterization of a phage against an Escherichia coli strain producing L-aspartase

Abstract:

[Objective] A phage was isolated from Escherichia coli CICC 11021S fermentation media, and its biological characterization was studied. [Methods] A phage designated CICC 80003 was isolated using the double-layer agar culture method. Phage morphology was observed by transmission electron microscopy. Gel electrophoresis of phage genome was carried out after genome extraction and treatment by endonucleases. We investigated the optimal multiplicity of infection, one-step growth curve, pH and temperature stability, and host range. Additionally, we analyzed the effects of CICC 80003 on cell growth and L-aspartase activity of CICC 11021S. [Results] The phage plaque was round and transparent, and showed clear aureole. The phage had a regular head of 50?60 nm in diameter and a long tail with 120?130 nm in length. The phage genome could be cut by endonucleases BamH I and Mlu I. The optimal multiplicity of infection was 0.1. The one-step growth curve showed a latent period of 5 min and a rise period of 25 min. The average burst size was about 86 phage particles per infected cell. The optimal pH was 8.0. The phage was completely inactivated when incubated at 90 °C for 15 min. Some of Escherichia coli and Salmonella spp. strains could be split by CICC 80003. No cell growth and L-aspartase activity was detected when phage contamination occurred. [Conclusion] CICC 80003 was a dsDNA phage and belonged to the family Siphoviridae, which could completely split E. coli CICC 11021S in broth.