Comparative Proteomic Analysis Of Three Lactobacillus Plantarum Based On The ITRAQ Technology

Currently,a variety of Lactobacillus plantarum strains are marketed as probiotics.L.plantarum has many physiological functions that are beneficial to human health.In addition to its health-promoting properties,its industrial importance also causes more and more attention.However,these applications imply that L.plantarum is challenged by high salt concentration.L.plantarum uses several adaptation strategies to cope with unfavourable osmotic conditions.Although there have been some studies on the osmotic stress response of L.plantarum,our understanding is incomplete.In this study,L.plantarum ATCC14917,L.plantarum FS5-5 and L.plantarum 208 of different sources were studied.We drew their growth curves in the medium without NaCl,and then kept the bacteria collected at logarithmic phase in the medium with 0%and 24%?w/v?NaCl for 3h respectively.Protein expression in the two kinds of salt stress conditions was also studied by iTRAQ technology,and finally verified the gene expression of difference protein selected using RT-qPCR.1.Growth curves were drawn respectively in medium without NaCl by measuring OD600nm.Growth curves showed that the time point of middle of logarithmic phase were 5 h,5 h and 6 h for L.plantarum ATCC14917,L.plantarum FS5-5 and L.plantarum 208 in medium without NaCl.2.Salt stress test of three L.plantarum collected in middle of logarithmic phase in medium without NaCl was performed.Then iTRAQ experiment was carried out after collecting bacteria.Experimental results showed that all the spectra identificated in uniprot_taxonomy₁578 were 350957,the spectra matched were 16669,the types of peptides identificated were 1628,and the total number of protein matched were 878.3.867 proteins were got from three L.plantarum under the comparation of 24%with 0%?w/v?,0%?w/v?and 24%?w/v?on the condition that differentially expressed multiples were above 1.2 and P-value<0.05.All the comparation showed that the difference in number of proteins showed increased expression and decreased expression was L.plantarum ATCC14917<L.plantarum FS5-5<L.plantarum 208,and the difference was small with L.plantarum ATCC14917 and L.plantarum FS5-5,but both were big with L.plantarum 208.4.Annotations of function and metabolic pathways of proteins were made through the Gene ontology?GO?and Kyoto encyclopedia of genes and genomes?KEGG?database,and then compared the protein annotated of three L.plantarum.Results also showed that the difference in number of proteins showed increased expression and decreased expression was small with L.plantarum ATCC14917 and L.plantarum FS5-5,but both were big with L.plantarum 208.This might indicate the salt stress ability of L.plantarum ATCC14917 and L.plantarum FS5-5 was near,and of L.plantarum 208 was poor.Therefore,the salt stress ability of three L.plantarum of different sources was different.Proteins showed significant expression mainly involved in carbohydrate metabolism,amino acid metabolism,nucleotide metabolism,protein biosynthesis,stress response and transporters under the condition of salt stress.5.The gene expression of selected difference proteins in iTRAQ was verified by RT-qPCR.Results showed that the gene expression level and protein expression level were almost the same,which verified the accuracy of iTRAQ results at the RNA level.