Construction and characterization of ialB-deleted strain of Brucella suis

Abstract:

The homologous genes of invasion-associated locus B (ialB) are conserved in Rhizobiales including Brucella spp., while little is known about this gene in Brucella. According to the limited reports, ialB of Brucella may be associated with the invasion into host cells and the adaptation to intracellular stress. [Objective] To explore the role of ialB gene in the Brucella adhering to and invading host cells and the intracellular survival of Brucella. [Methods] We constructed the ialB-deleted strain ΔialBof Brucella suis S2 by using homologous recombination method and the complemented strain CΔialB by transforming the expression plasmid containing the open reading frame of ialB into ΔialB. Subsequently, we compared the growth phenotype and stress resistance of different strains and assessed the effect of ialB deletion on the expression of genes associated with the polar cell elongation of Brucella. Additionally, we determined the effect of ialB deletion on the invasion and proliferation of Brucella in RAW264.7 murine macrophages. [Results] ΔialB and CΔialB were constructed successfully. Compared with B. suis S2, ΔialB showed suppressed growth and decreased cell viability. The deletion of ialB decreased the resistance of Brucella to acid stress, hypertonic stress, hypotonic stress, and polymyxin-B stress and increased the resistance to oxidative stress. Furthermore, the deletion changed the cell morphology of Brucella, which was manifested as shortened cell length and increased cell diameter. The mRNA levels of the genes associated with the polar cell elongation of Brucella were down-regulated in ΔialB. Compared with B. suis S2, deletion of ialB did not change the adhesion or invasion of Brucella and decreased the proliferation in RAW264.7 cells. [Conclusion] ialB is associated with the cell viability and polar growth of Brucella, playing a role in the stress resistance and proliferation of Brucella in host cells.