Comparison of Genomes of Brucella melitensis M28 and the B. melitensis M5-90 Derivative Vaccine Strain Highlights the Translation Elongation Factor Tu Genetuf2as an Attenuation-Related Gene

Abstract

ABSTRACTBrucella melitensiscauses brucellosis, a disease affecting sheep, cattle, and sometimes humans. AttenuatedB. melitensisstrain M5-90, derived from virulent strain M28, is widely used as a live vaccine in ruminants in China. Genetic differences between the strains may cast light on the mechanism of attenuation. We recently reported the complete genomic sequences of M28 and M5-90. Genome organization is highly conserved between these isolates, and also with virulent strains 16 M and ATCC 23457. Analysis revealed 23 open reading frames (ORFs) with consistent differences between M5-90 and the virulent strains. Notably, thetuf2gene encoding translation elongation factor EF-Tu from M5-90 contained 50 single nucleotide polymorphisms (SNPs) and 9 gaps (indels) compared totuf2of M28 or of the other virulent strains. There were no changes intuf1. To evaluate the potential role of EF-Tu in pathogenesis,tuf1andtuf2mutants of M28 and an M5-90 strain harboring wild-typetuf2were constructed, and their virulence/attenuation was evaluatedin vivo. We report that thetuf2gene plays an important role in the attenuation of M5-90 virulence.