Isolation and biological characteristics analysis of a bacteriophage of Enterococcus faecalis

Abstract

ObjectiveTo isolate and identify a bacteriophage of Enterococcus faecalis and to analyze its biological characteristics.MethodsThe host bacteria was isolated from the process of yak slaughtering and identified by 16S rRNA sequencing. The bacteriophage was isolated from the environmental sewage and was purified. The titer of bacteriophages was determined using the double-layer plate method. The morphology of bacteriophage was observed by transmission electron microscopy； the bacteriophage lysis profiles， optimal infection complex， and one-step growth curve were determined； the effects of pH， UV irradiation， temperature， and organic solvents on bacteriophages have been studied. Furthermore， the lytic activity of the bacteriophage against the host bacteria was determined.ResultsThe host bacteria were identified as E. faecalis by 16S rRNA sequencing. A bacteriophage named P45 was isolated from sewage to lyse E. faecalis. Electron microscopy showed that the bacteriophage was a tadpole-shaped long-tailed bacteriophage， which has a hexahedral head and its length is （200±5） nm. The bacteriophage had obvious lysis effect on four strains of E. faecalis. Bacteriophage’s optimal multiplicity of infection was 0.1. The results of one-step growth curve showed that the incubation period was 50 min， the lysis period was 190 min， and the burst size was 1 PFU/cell. This bacteriophage survived at pH=2 to 3，which titers were 1.05×102 PFU/mL and 1.85×103 PFU/mL. At 75 ℃， this bacteriophage was completely inactivated. Bacteriophage’s titer was decreased by UV irradiation， and it was not sensitive to organic solvents.ConclusionThis bacteriophage has a good lysis effect and has potential application on the prevention or control of E. faecalis contamination.

Keywords

• enterococcus faecalis
• bacteriophage
• biological characteristics
• lytic effect