Breeding And Resistant Mechanism Of Anti-phage Mutant Lactobacillus Plantarum Strain

Bacteriophage pollution in dairy industry is considered as one of the important problems to be solved urgently.Spontaneous phage-resistant strain was isolated from its host strain Lactobacillus plantarum IMAU10120 by secondary infection method using Lactobacillus virulent bacteriophages P1 and P2.The changes of adsorption characteristics,adsorption receptor and fermentation characteristics of the mutant strain were evaluated in compared with the host strain.Moreover,the mutation sites were located by whole genome sequencing,and the phage-resistant mechanism was tried to be elucidated.The results showed that:1)A phage-resistant mutant IMAU10120-1 to phage P1 and P2 was successfully screened by secondary infection method.This strain is non-lysogenic,and possess stable inheritance resistant properties.2)The adsorption rate of phage P1 on the anti-phage strain increased by 3.01%(92%for the sensitive strain),and the adsorption rate of phage P2 on the anti-phage strain showed no significant difference in compared with the host strain(P >0.05),which might mean the anti-phage ability of mutant strain was independent with adsorption.3)Fermented soymilk by phage-resistant strain had stable physical and chemical properties during the storage period,with high viable count,viscosity and water-holding capacity.Moreover,there was no significant difference(P >0.05)between the mutant strain and host strain in flavor,odor and acceptability.Its fermented properties were in similar with those of host strain.4)Whole genome sequencing and comparative analysis showed that 11 genes with14 sites were mutated,involving the metabolic pathway changes of small subunit ribosomal protein S14,ABC-2 type transport system ATP-binding protein(ABC-2.A),shikimate kinase(aro K)and osmoprotectant transport system permease protein(opuBD),which might lead to the blocking of transcription and translation of phages.In this study,an anti-phage mutant Lactobacillus plantarum strain was screened out,its related characteristics were studied.The possible mechanism of its anti-phage property was preliminary analyzed,which may provide some theoretical and technical basis for the application of anti-phage strains in industrial processing in the future.