Safety Assessment Of Lactobacillus Gesseri JDM511

As people are living a better live nowadays, food safety has become a heated topic. Food safety is a interdiscipline science to promote public health and to improve the living standard. There are different laws and regulars in this fields both at home and aboard.In first part of this work,we sequenced the complete genome of Lactobacillus gasseri JDM511 with a GS 20 system(454 Life Science Corporation).The complete genome of Lactobacillus gasseri JDM511 contains a single, circular chromosome of 1,788,466 bp, a small plasmid of 39,184 bp and a big plasmid of 93,309 bp. The overall GC content of the chromosome is 35.06%.The whole genome codes 1705 protein coding genes,66 t RNA coding genes and 3 r RNA operons. When compared with ATCC 33323,JDM511 has a smaller genome and fewer protein coding genes.12% of total protein is related to the carbohydrate metabolism and transport. 18 glycoside hydrolase genes including glucosidase, amylase,galactose and maltose were found.Secondly,this work combined the complete genome sequence and traditional phenotype to evaluate the safety of JDM511. According to the E-test result, JDM511 shows high resistant to 5 antibiotics: AK, BA, CI, SM and VA, moderate resistance to,TC,GM and RI,while is sensitive to CT,AC, AM, TS, CE, IP, EM and CL. The result is consistent with the spectrum of Lactobacillus. JDM511 does not have the ability to produce biogenic amines such as tyramine, histamine, putrescine, cadaverine, spermine and tryptamine. There is no other amino acid decarboxylase genes in JDM511 besides Oxalyl-Co A decarboxylase. After compared with ARDB,VFDB and other know adverse metabolism related genes, 43 antibiotic resistance genes, 152 putative virulence factors and 11 adverse metabolism related genes were found. There are 1 possible phage related fragment, 1 possible CRISPR and 9 IS elements but no complete prophage on the genome of JDM511. Althogh several antibiotic resistance genes, virulece factors and adverse metabolism related genes were identified, but what should not be ignored is that there are no toxin gene or highly transferable adverse gene and none of these safety related genes is on or near the mobile elemets.This work have combined the traditional phenotype with the genomics to make a safety assessment of Lactobacillus gasseri JDM511. This is a more comprehensive method when compared with old one. It can reveals the potential safety issues and related molecular mechanism at utmost to provide foundation and shed light to other study.In second part of this work,we confirm that Clp can degradate the antitoxin protein 812,which means it takes part in the activation of type ⅡTAs in B. longum JDM301. Toxin-Antitoxin system plays an important role in the regulation of bacteria growth.In third part of this work,we measured the content of aflatoxin B1 contained in the rice samples from different origins and grown in different regions. Aflatoxin is secondary metabolites of some fungi.The results showed that the aflatoxin contained in rice are generally low.And the measure values of the samples that were grown in the north of Jiangsu province are higher than those were grown in the north and east China.The values of the samples bought from super marketss and small groceries are obviously different. Non-qualified samples are found in groceries and medium markets.