Whole Genome Sequencing And Comparative Genomic Analysis Of Brucella Abortus A19

Brucellosis,which is caused by a group of Gram-negative bacteria of the genus Brucella,is a major allergic infectious zoonotic disease.It leads to huge economic losses and serious public health problem.Currently,vaccination is the main approach of prevention and control of brucellosis.Brucella abortus strain A19 is a vaccine strain that is widely used for brucellosis prevention in China.This study is committed to elucidate Brucella abortus strain A19 genomic information and the main functions of its genes.Through the comparison with the strain S19,it may help us further understand the differences between the two vaccine strains,indicating the research direction for the development of brucella vaccine.The paper contains two parts:Part one:Whole genome sequencing of Brucella abortus A19StrainBrucella abortus A19 genomic DNA was sequenced using Illumina Hiseq2000 sequencing analyzer through 100-fold(100×)genome coverage.By comparison with the published genome sequence of B.abortus S19,the order and orientation of the contigs assembled were determined and leftover gaps were amplified and sequenced by Sanger sequencing for comprehensive closure of the genome.The 3.28Mb B.aborlus A19 genome is comprised of two circular chromosomes:one 2122576 bp(chrl)and the other 1162241(chr?)in length.In the B.abortus A19 genome,3295 putative protein coding genes with an average length of 864 bp were predicted,covering 86.7%of the genome.Besides,a total of 55 tRNA genes,9 rRNA genes,9 genomics islands and 1 possible crispricer were predicted by corresponding databases.A whole genome Blast search was performed against COG,GO,KEGG,NR databases for genome annotation,and 2625,2385,2140,3235 genes were annotated respectively.In addition,55 genes which may be involved in pathogen host interactions,79 potential virulence factors,1 antibiotic resistance gene and 160 secretory proteins were predicted.Part two:Comparative genomic analysis of Brucella abortus A19A systematic comparative analysis of B.abortus A19 strain with B.abortus S19 was carried out to illuminate similarities and differences between the two vaccine strains on a genome-wide scale.Alignment results demonstrate that the two strains have perfect collinearity and no translocation and inversion occurrence was observed.However,a total of 6026 SNPs and 306 insertion-deletions were identified,which affected 1795 genes with nonsynonymous mutation or premature-stop.The 702bp deletion in the ery operon was also observed.Cluster results of COG database show that most affected genes were involved in the metabolism pathway.And among the 1795 genes,6.7%(121/1795)was experimentally confirmed to be virulence-related genes.Overall,comparative analysis in this study might be helpful for further understanding of differences between the two vaccine strains and provide resources for further study and improvement of brucellosis vaccines.