Completion of the Genome Sequence of Brucella abortus and Comparison to the Highly Similar Genomes of Brucella melitensis and Brucella suis

Abstract

Brucellosis is a worldwide disease of humans and livestock that is caused by a number of very closely related classical Brucella species in the alpha-2 subdivision of the Proteobacteria. We report the complete genome sequence of Brucella abortus field isolate 9-941 and compare it to those of Brucella suis 1330 and Brucella melitensis 16 M. The genomes of these Brucella species are strikingly similar, with nearly identical genetic content and gene organization. However, a number of insertion-deletion events and several polymorphic regions encoding putative outer membrane proteins were identified among the genomes. Several fragments previously identified as unique to either B. suis or B. melitensis were present in the B. abortus genome. Even though several fragments were shared between only B. abortus and B. suis, B. abortus shared more fragments and had fewer nucleotide polymorphisms with B. melitensis than B. suis. The complete genomic sequence of B. abortus provides an important resource for further investigations into determinants of the pathogenicity and virulence phenotypes of these bacteria.Brucellosis is a bacterial disease of animals that can be transmitted to humans. The primary impact of brucellosis stems from losses due to reproductive failure in food animals and the loss of human productivity. Since brucellosis threatens the food supply and causes undulant fever, a long, debilitating disease in humans, Brucella species are recognized as potential agricultural, civilian, and military bioterrorism agents. Brucellosis in food animals is controlled by vaccination. Human brucellosis is treatable with antibiotics, though the course of antibiotic treatment must be prolonged due to the intracellular nature of Brucella.Analysis of 16S rRNA sequences places Brucella spp. as members of the alpha-2 Proteobacteria (31). The genus Brucella has six recognized species, all of which exhibit distinct host preferences (25,26). The high degree of similarity among the brucellae (1, 3, 13, 33) lends support to the proposal that the classical species of Brucella are actually strains of Brucella melitensis (40). However, this view conflicts with the hypothesized evolutionary isolation of these classical species due to their intracellular existence and host preference (29). Common host-pathogen associations among the classical Brucella species are as follows: B.

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

“…abortus 9-941 ( Halling et al, 2005), B. suis ( Paulsen et al, 2002), B. canis ( Wattam et al, 2009), B.…”

Genomic analysis of the original Elberg Brucella melitensis Rev.1 vaccine strain reveals insights into virulence attenuation

“…Blat search analysis revealed a similar RD in B. canis and B. suis 1330. The importance of this RD in the attenuation of Rev.1 is questionable, as ureE in cluster 1 had previously been shown to be a pseudogene in B. melitensis and B. suis [23]. RD2 is located downstream of BMEI1888, which encodes lactoylglutathione lyase, and RD3 is located at the 5ʹ end of BMEII0784, which encodes a putative hydroxlase.…”

Taking the pseudo out of pseudogenes

“…intracellular lifestyle results in frequent fixation of nonsense mutations within the population: Non-synonymous/synonymous (dN/dS) substitutions in intracellular bacteria regularly reach rates of 1, outstripping that of free-living bacteria [15]. Non-sense mutations and frameshifts frequently create pseudogenes by introducing premature stop-codons, or by destroying promoters [16,17], start-codons [18], or functional domains [16,19]. Horizontal gene transfers are probably the major source of pseudogenes in prokaryotes, as the majority of the genes transferred likely provide few benefits and are rapidly silenced due to a lack of positive selective pressure.…”