Screening And Characteristics Of Phage P1 Resistant Lactobacillus Plantarum Strain

Spontaneous phage-resistant mutant was screened out from Lactobacillus virulent phage P1 and its host strain Lactobacillus plantarum IMAU10120 by using secondary culture method.To evaluate the influence of phage resistance changes on its phenotypic characteristics,the phage resistance,adsorption property and receptors,as well as fermentative properties were determined.To analyze the possible reason of antiphage properties,the differences between the mutant strain and sensitive strain were compared by using whole-genome resequencing.The results showed that:(1)A spontaneous phage-resistant Lactobacillus plantarum mutant was successfully screened out.As a non-lysogenic strain,the phage-resistant mutant showed complete resistance on phage P1 which could be steady inherited.(2)The data of whole-genome resequencing showed the identity between mutant strain and parent strain.Some variations were observed in the mutant genome,including the absence of three plasmids and eight mutations involving six genes,which may result in structural change of the translated protein or different gene expression that cause abnormal protein function.Moreover,phage proliferation and release might be influenced by metabolic pathway regulation,and then cause phenotype change and produce phage resistance.(3)The adsorption rate of mutant didn't change obviously(>97%),which indicated that phage receptors were not mutated.Moreover,the adsorption receptor of phage P1 might be polysaccharide polymer which was connected with the peptidoglycan.(4)The fermentative characteristics between mutant strain and sensitive strain were similar and had no significant difference(P>0.05).It can be used as a substitute strain of the sensitive isolates.This study screened out a phage-resistant Lactobacillus plantarum strain and studied on its relevant characteristics,which may provide theoretical data support for the in-depth exploration of antiphage mechanism and lay the foundation for the breeding and development of antiphage strain.