| Pseudomonas aeruginosa is a common opportunistic pathogen in nature.It can cause a series of human infections.At the same time,it is also the main pathogen leading to food corruption.In recent years,the widespread use of antibiotics has led to the frequent emergence of drug-resistant strains.The emergence of drug-resistant strains has posed a serious threat to food safety and environmental health.Bacteriophages as bacteriostatic agents and antibiotics can achieve bacteriostatic effects.Bacteriophages as bacteriostatic agents can specifically inhibit the growth of bacteria.At the same time,they are also growing.Compared with antibiotics,they have better application prospects.Therefore,it is urgent to develop new fungicides.In this study,the basic biological characteristics,genomics,taxonomy,antibacterial activity and application of Pseudomonas aeruginosa phage K4 isolated in our laboratory were analyzed and studied.The results of one-step growth curve showed that the incubation period of phage K4 was about 15 min and the release amount was about 85 pfu/infection center;Bacteriostatic curve showed that bacteriophage K4 had obvious inhibitory effect on host bacteria under different infection complex(MOI);The results of stability experiment showed that bacteriophage K4 had good thermal stability,chloroform stability and acid-base stability;The results of host range analysis showed that phage K4 could not lyse the PAK strain with deletion of wbp R,wbp T,wbp V,wzy,ssg,BN889＿05221 genes,all of which are related to the synthesis of LPS,that is,related genes for the biosynthesis of O-specific antigen(OSA).Therefore,it is speculated that the receptor of Pseudomonas aeruginosa phage K4 is OSA..Genomic analysis showed that phage K4 was a linear double stranded DNA molecule with a 74 bp forward terminal repeat.The length of phage K4 genome is 50358 bp,with 77 protein coding genes,encoding 46 hypothetical proteins and 31 proteins with hypothetical functions,including functional proteins involved in replication,transcription,DNA repair,phosphate metabolism and 1 t RNA Arg;We selected 8 strains of Pseudomonas aeruginosa phages for comparative genomic analysis,and selected phages with the same protein function at the amino acid level to analyze the evolutionary tree of their main capsid proteins and large subunits.Comparative genomics showed that the genome of phage K4 shared an identity of95.08% with Pseudomonas virus PA11 which belongs to the Paundecimvirus genus of the Zobellviridae family,suggesting that phage K4 may be a new member of the Paundecimvirus genus.The application experiment showed that in the experiment of the effect of bacteriophage K4 on bacteria in milk,when the MOI of bacteriophage was 1 and 10 at 4°C,the bacteriostatic efficiency was 93.73% and 99.02% respectively,and the bacteriophage increased 71 and 22 times respectively;At 25°C,when the MOI of phage was 1 and 10,the bacteriostatic efficiency was 79.29% and 98.84% respectively,and the bacteriophage increased 149 and142 times respectively.In the effect experiment of bacteriophage K4 on bacteria in lunch meat,the bacteriostatic efficiency was 96.34% and 88.28% when the MOI of bacteriophage was 1 and 10 at 4°C,and the bacteriophage increased by 3 times and 6 times respectively;At25°C,when the MOI of phage was 1 and 10,the bacteriostatic efficiency was 94.89% and99.15% respectively,and the bacteriophage increased 33 and 78 times respectively.The experimental results show that bacteriophage K4 can significantly inhibit the growth of host bacteria in samples such as milk and ready-to-eat beef,and the number of bacteriophages has also increased significantly.It is suitable to be used as an antibacterial agent in the field of food safety.The results showed that bacteriophage K4 grew fast and had strong bactericidal activity,and the genome did not carry genes encoding integrase,resistance and virulence factors.Therefore,phage K4 can be used to control the pollution of Pseudomonas aeruginosa in food. |
PDF Full Text Request