Study On Pathogenicity Of Listeria And Functional Analysis Of Partial Genes

Listeria is a gram-positive parasitic bacteria in the cell,which belongs to the seven species.According to the pathogenicity,there is divided into two major categories.It represents the Listeria monocytogenes can adapt to various environments?such as low temperature,high pH,high salt concertration,etc.?and can infect many animals from humans to insects.Murry first reported Listeria in1962,this disease has been occurring in many countries,especially in the last 20years,the food poisoning caused by listeria monocytogenes has become increasingly serious.In order to further study the pathogenicity of listeria,this paper completed the following studies:?One?Study on three listeria strains infected miceIn order to study virulence difference among Listeria monocytogenes?Lm?,L.ivanovii?Li?and L.welshimeri?Lw?,three kinds of bacteria were inoculated in Kunming mice to establish artificial infection model,and the clinical symptoms of mice were observed.The pathological observation was made on the characteristic pathological tissues from liver,spleen,lung and kidney paraffin slices.It was observed that the typical symptoms of infected mice were 2 to 5 days after the infection,but after 7 days,they basically recovery.The pathogenicity of listeria monocytogenes is the most serious,mainly damaging the kidney and liver,and the second is L.ivanovii,which mainly damages the spleen and liver.The pathogenicity of L.welshimeri is the weakest,which mainly damages the lung and liver.It is shown that Listeria monocytogenes has the strongest pathogenicity in mice,followed by L.ivanovii,and the pathogenicity of L.welshimeri is the weakest.?Two?Transcriptional study on macrophages infected by listeria monocytogenes.To study the molecular mechanism of virulence and pathogenicity of Listeria monocytogenes,macrophages?RAW264.7?were infected in abdominal cavity by it at the optimum ratio of 1:35 through gradient screening.The total RNA of the Listeria monocytogenes after infected 0 h,4 h and 8 h were extracted and sequenced.The sequencing results were analyzed.There were 578 differential expression genes,including 487 down-regulated genes and 91 up-regulated genes.The GO enrichment analysis showed that there were 1 090 genes with differential expression genes,of which 137 up-regulated genes and 953 down-regulated genes.These genes belong to three major categories in GO terms:601 genes related to biological processes,449related to molecular function,and 40 related to cell components.The differential expression genes were compared in the KEGG database,and 710 genes in all the differential expression genes were noted in 170 different physiological pathways.In the process of stress reaction,the bacteria can adjust the number and activity of various intracellular enzymes to adapt to the new environment through different environmental signals.In the process of infection,the decrease in the synthesis efficiency of ribosomal protein was related to the decrease of L25 protein expression.The sRNA structure found that the predicted target gene concentration was enriched to the activity of methyltransferase,the function of ABC transporter,the function of RpiR family transcriptional regulatory agency and the activity of replication of DNA helicase.?Three?Functional analysis of Sigma B and Zurr.It has been reported that Sigma B and Zurr genes play an important regulatory role in bacillus subtilis,bacillus cereus and staphylococcus aureus.In order to further study regulatory mechanisms of these genes,specific primers is designed to amplify and construct the cloning vector.The related bioinformatics analysis of amino acid composition,antigen index,epitope,secondary structure and tertiary structure prediction were carried out.Sigma B may play a role in many processes,such as DNA binding transcription factor activity,nucleic acid-binding transcription factor activity,protein-binding transcription factor activity,and core RNA polymerase binding transcription factor activity etc.The Zurr gene also play regulatory role in binding transcription factors,nucleic acid binding,DNA binding,cation binding,metal binding and have the effect of coordinating the absorption Zn²⁺from the external environment.