Pan-Genome of Brucella Species

Whole-genome sequencing of bacterial pathogens has high impact on diagnosis and development of prophylaxis to human and veterinary disease. To study the genetic variations and relatedness among Brucella spp., we have examined the pan-genomic content of 18 Brucella complete genomes from NCBI using GView and Panseq server. Multiple sequence alignment of 16S rRNA gene sequences and multiple genome alignment of all 18 Brucella spp. showed high conservation at the nucleotide level. The core, accessory and unique gene content of Brucella spp. were estimated to be 2473, 7972 and 235 respectively. The presence of strain specific region in chromosome 1 of B. melitensis M5-90 and chromosome 2 of B. microti CCM 4915, B. pinnipedialis B2/94, and B. suis ATCC 23445 were identified. In addition, a stretch of genetic pool harboring 206 strain specific coding genes trans-located from chromosome 1 to chromosome 2 were also identified in the genome of B. suis ATCC 23445. Pan-genome analysis has also revealed the integration of strain specific 23 CDS (57.82 Kb) and 6 CDS (12 Kb) in B. pinnipedialis B2/94 and B. microti CCM 4915, respectively. Major pathogenic determinants like virB operon, non-classical lipopolysaccharide, two-component system BvrR/BvrS and cyclic beta-1, 2-glucan synthase were unanimously found in all Brucella spp.. The virulence genes such as flagella, type III secretion system, hemolysins, outer membrane proteins, acvB, MViN and genes involved in eryrthritol metabolism were found in the accessory genome, which may guide the host specificity.