Genome Sequence of Brucella abortus Vaccine Strain S19 Compared to Virulent Strains Yields Candidate Virulence Genes

Abstract

The Brucella abortus strain S19, a spontaneously attenuated strain, has been used as a vaccine strain in vaccination of cattle against brucellosis for six decades. Despite many studies, the physiological and molecular mechanisms causing the attenuation are not known. We have applied pyrosequencing technology together with conventional sequencing to rapidly and comprehensively determine the complete genome sequence of the attenuated Brucella abortus vaccine strain S19. The main goal of this study is to identify candidate virulence genes by systematic comparative analysis of the attenuated strain with the published genome sequences of two virulent and closely related strains of B. abortus, 9–941 and 2308. The two S19 chromosomes are 2,122,487 and 1,161,449 bp in length. A total of 3062 genes were identified and annotated. Pairwise and reciprocal genome comparisons resulted in a total of 263 genes that were non-identical between the S19 genome and any of the two virulent strains. Amongst these, 45 genes were consistently different between the attenuated strain and the two virulent strains but were identical amongst the virulent strains, which included only two of the 236 genes that have been implicated as virulence factors in literature. The functional analyses of the differences have revealed a total of 24 genes that may be associated with the loss of virulence in S19. Of particular relevance are four genes with more than 60bp consistent difference in S19 compared to both the virulent strains, which, in the virulent strains, encode an outer membrane protein and three proteins involved in erythritol uptake or metabolism.

The mglA gene and its flanking regions in Brucella: The role of mglA in tolerance to hostile environments, Fe-metabolism and in vivo persistence

“…Taken together with differences in the flanking regions, this gene locus may thus be interesting not only for diagnostic purposes ( Table 1), but also with respect to virulence and pathogenesis. So far, the most relevant difference between the virulent and chronically persisting strain B. abortus 2308 and the vaccine strain B. abortus S19 has only been described for erythritol-catabolism ( Crasta et al, 2008 andSangari et al, 2000). Most interestingly, the differences in the mglA genome region enable similar conclusions as the results of a phylogenetic 'clade' system, based on whole-genome comparisons ( Wattam et al, 2009), which describes B. ovis as an 'ancestor'…”

Erythritol feeds the pentose phosphate pathway via three new isomerases leading to D-erythrose-4-phosphate in Brucella

“…These steps involve three enzymes that have not been described for any other species. Because the role of TpiA2 and RpiB in the metabolism of erythritol is now established, we propose to rename their genes eryH and eryI [the designations eryE, eryF, and eryG have already been proposed for the erythritol transport system of B. abortus (21)]. The gene encoding the putative regulatory protein DeoR, which precedes tpiA2 on the chromosome, has been designated eryR by Geddes and colleagues (13).…”

INFECTION OF C57BL/6 MICE BYTRYPANOSOMA MUSCULIMODULATES HOST IMMUNE RESPONSES DURINGBRUCELLA ABORTUSCOCOLONIZATION

“…Despite genetic differences of B. abortus S19 from wild-type strains commonly isolated in nature (Crasta et al 2008), S19 has been shown to cause disease in mice that is similar to that in large animals, especially in the reproductive tract, supporting its utility as an effective model (Enright et al 1990;Kim et al 2005). The selection of T. musculi, the patho-adapted species of trypanosome for mice, was based on the benign nature which appeared similar to reports of T. cervi in elk (Albright and Albright 1981).…”