Screening Of Uric Acid-lowering Lactic Acid Bacteria And Analysis Of Its Whole Genome Sequence

At present,the main way to treat hyperuricemia is to add drugs on the basis of diet control.Studies have shown that probiotics can reduce the level of uric acid in the human body,thereby achieving the effect of preventing and treating hyperuricemia.In this thesis,the lactic acid bacteria isolated from traditional dairy products were used as the research object,and the ability of lactic acid bacteria to degrade nucleosides and inhibit xanthine oxidase was used as an index,bile salt tolerance,gastrointestinal tolerance,cell adhesion ability,antibacterial ability and drug sensitivity evaluation and molecular biology identification.And further use the whole genome sequencing technology to analyze the genome components of the target strain to mine its genetic information.The following results were obtained from the above study:(1)Seven strains of lactic acid bacteria with higher purine nucleoside degradation rate were screened from 80 strains of lactic acid bacteria,namely: strains NL02,NL07,NL27,NL37,NL46,NL59 and NL68,the degradation rates of inosine and guanosine were above 74%.(2)The test results of the inhibition effect of these seven strains of lactic acid bacteria on xanthine oxidase showed that the intracellular and extracellular substances of the seven strains had different degrees of inhibition on xanthine oxidase(XOD).Among them,the intracellular and extracellular substances of strains NL02,NL07,NL27,NL37 and NL46 have higher inhibition rates of XOD,all above 25%,and have good xanthine oxidase inhibition ability.(3)The probiotic potential test results of the above 5 strains of lactic acid bacteria showed that,The strains NL02,NL07,NL27 and NL37 have certain tolerance under acidic conditions;The bile salt tolerance of strains NL02,NL27 and NL37 was stronger;Strains NL02 and NL27 performed outstandingly in subsequent artificial gastrointestinal fluid tests.(4)The results of antibacterial ability,cell adhesion ability and drug susceptibility test showed that,Strain NL02 has different degrees of inhibitory effect on Escherichia coli,Staphylococcus aureus and Salmonella typhimurium;it has strong adhesion to HT-29 cells,and the adhesion ratio is 5.56±0.87 CFU/cells;and it does not have the ability to 10 kinds of antibiotics.Strain NL02 was identified as Lactobacillus reuteri by16 S r DNA sequencing analysis.(5)The whole genome of Lactobacillus reuteri NL02 was sequenced,and the information of related genes such as its genetic composition,metabolic characteristics and probiotic function was systematically analyzed.The results show,The whole genome contains one circular chromosome and two plasmids,with sizes of 2073208 and 24912 and 13866 bp,and GC contents of 38.80%,37.74% and 41.25%,respectively.There are a total of 2085 protein-coding genes(CDSs)in the whole genome.The COG,GO,KEGG and CAZy databases were used to annotate the whole genome of Lactobacillus reuteri NL02,and the membrane transport and carbohydrate metabolism-related functions encoded in the genome were found.The gene abundance is very high,indicating that it has a very strong metabolic potential.And found 15 genes related to acid tolerance,1related to bile salt tolerance,6 related to adhesion,and 8 related to antibacterial substances in its genome.The strain does not have mobile genetic resistance elements;and its genome also also encodes related enzymes for guanosine and inosine metabolism,it was further verified that Lactobacillus reuteri NL02 has good probiotic properties and the ability to degrade purine nucleosides.This study can provide basic data for animal or clinical trials of lactic acid bacteria to reduce uric acid,and also provide excellent bacterial resources for the prevention and treatment of hyperuricemia and other uric acid metabolism diseases.