Studies On The Biological Characteristics Of Lactobacillus Plantarum Virulent Phage P2

Lactic acid bacteria are considered as beneficial species and are widely used in fermented food industry to produce dairy products,meat products and animal silage.In the process of fermentation,phages often infect lactic acid bacteria,resulting in slow or even a complete fermentation failure.This will result in a huge economic loss for the producer.Therefore,the contamination of bacteriophage is considered as one of the most serious threats in the food fermentation industry.In this study,Lactobacilus plantarum virulent bacteriophage P2 was isolated and purified from a slow fermentation containing Lactobacilus plantarum.Morphology,resistance to pH and temperature,as well as adsorption ability under different pH,temperature,divalent cations and chloramphenicol were evaluated.Moreover,phage resistant properties of different Lactobacillus plantarum strains to phage P2 were examined.Electron microscopy results showed that Lactobacillus plantarum virulent phage P2 belonged to the Stylovinidae type B1 family;it has an isometric head with a diameter of 66.67 ± 3.00 nm and a non contractile tail of 216.67±3.00 nm in length and 12.25 ± 3.00 nm in width.Its latent period was 30 min with a burst time of 135 min,and average burst size of 214.49 ± 3.98 PFU.The survival rate of phage pH P2 was evaluated over a pH range of 2?11.Results indicated that it was totally inactivated at pH 2 and 3.When the pH increased from 6 to 9,the survival rate increased more than 80%:pH 8 appeared as optimal for survival.At 50? where the survival rate decreased to 12.89%.The adsorption rate of phage over a pH 5?9 exhibited no obvious effects:in all case the adsorption rate was more than 90%.At a pH of 4,10 or 11,the adsorption rates decreased,but stil]maintained values greater than 50%.Temperature other than at 50?had little effect on the adsorption rate(>88.29%)of the phage.Calcium can improve adsorption ability,but magnesium showed adsorption ability decreased;the effect was Ca2+>Control>Mg2+.Chloramphenicol did not show obvious influence on the phage's adsorption ability.After treated for 30 min,the adsorption rate still can reach to 90.19%.Thirty-eight Lactobacillus plantarum strains were evaluated with respect to phage infectivity;only three strains(NM20-4,WH6-1-1 and NM24-2)were sensitive to virulent phage P2,indicated that higher infection specificity.In the present study,the biological properties of Lactobacillus plantarum virulent phage P2 were analyzed.The information obtained can be used to enrich the database of lactobacillus phages,and provide a basis of information for the control of this phage in the fermentation industry.