Biological properties of the virulent bacteriophage RAP44 sensitive to Riemerella anatipestifer

To explore the potential clinical application of the virulent bacteriophage RAP44 sensitive to Riemerella anatipestifer,the biological properties of the phage were detected by the conventional method.It had relatively high stability from pH 5 to pH 9.It still remained high lysis activity after being incubated at 55 ℃ for 30 min.After 15 mmol/L Mg2+ or 20 mmol/L Ca2+ were added to the medium,the numbers of plaques were 61.9% and 53.8% higher than into the medium without Mg2+ or Ca2+ respectively.The optimal multiplicity of infection was 0.025.The latent period was about 10 min,burst period was 40 min,and the average burst size was about 83 PFU/cell.SDS-PAGE profiles indicated that RAP44 contained two capsid proteins,and the two capsid proteins were 40 ku and 17 ku in molecular weight respectively.The genome of the phage was about 40 kb in size.The latent period of phage RAP44 was short and the average burst size was great,indicating that it could be used as a candidate phage strain for biological control R.anatipestifer.