Insights into irr and rirA gene regulation on the virulence of Brucella melitensis M5-90

Abstract

Iron is a fundamental element required by most organisms, including Brucella. Several researchers have suggested that the iron response regulator (irr) and rhizobial iron regulator (rirA) genes regulate iron acquisition by Brucella abortus, influencing heme synthesis by and virulence of this pathogen. However, little is known about another Brucella species, Brucella melitensis. In this research, we successfully constructed two mutants: M5-90Δirr and M5-90ΔrirA. The adhesion, invasion, and intracellular survivability of these two mutants were evaluated in RAW264.7 cells infected with 1 × 106 CFU of M5-90Δirr, M5-90ΔrirA, or M5-90. We also tested the sensitivity of cells to hydrogen peroxide and their ability to grow. In addition, the virulence of these two mutants was evaluated in BALB/c mice. The results showed that the ability of these two mutants to invade and adhere inside the murine macrophages RAW264.7 was attenuated but their ability to replicate intracellularly was strengthened, enhancing the resistance to hydrogen peroxide. The M5-90Δirr mutant showed stronger growth ability than the parental strain under iron-limiting conditions. No differences were observed in the number of bacteria in spleen between M5-90 and M5-90Δirr at 7 or 15 days postinfection. However, the number of M5-90ΔrirA in spleen reduced significantly at 15 days postinfection. The splenic index of the M5-90Δirr group is evidently lower than that of M5-90. This is the first report that irr and rirA genes of B. melitensis are associated not only with virulence but also with growth ability. Together, our data suggest that M5-90Δirr is a promising Brucella vaccine candidate.

Using a Relative Quantitative Proteomic Method to Identify Differentially Abundant Proteins in Brucella melitensis Biovar 3 and Brucella melitensis M5-90

“…Additionally, the iron uptake system also plays a role in the virulence of Brucella and pseudomonas aeruginosa . Mutation of the iron uptake system leads to the attenuation or even an avirulent phenotype both in vitro and in vivo ( 30 , 31 ). Results of KEGG database analysis in our study indicate that the Brucella Zur protein (encoded by gene BMEII0175 , protein accession: Q8YDK0) is indirectly associated with iron uptake and this protein is over-represented in the Y3 strain ( Table S3 ).…”

“…Results of KEGG database analysis in our study indicate that the Brucella Zur protein (encoded by gene BMEII0175 , protein accession: Q8YDK0) is indirectly associated with iron uptake and this protein is over-represented in the Y3 strain ( Table S3 ). In addition to the Irr and RirA proteins that are involved in iron transport in Brucella ( 31 ), Zur might be another regulatory protein involved in Brucella iron metabolism. It has been discovered that ABC transporters are crucial virulence factors in Streptococcus pneumoniae and Escherichia coli ( 32 , 33 ).…”

Integrated mRNA-seq and miRNA-seq analysis of goat fibroblasts response to Brucella Melitensis strain M5-90

“…Previous research focused on identification of B. melitensis M5-90 virulence factors ( Li et al, 2015 ; Zhang et al, 2020 , 2017 ) and elucidating unique gene expression profile of mouse infected macrophages ( Wang et al, 2011b ; Xu et al, 2021 ). In macrophages, it has already been observed that the two-component system BvrR/BvrS of B. meliten sis is required to modulate bacterial physiology and the shift from extracellular to intracellular life ( Martín-Martín et al, 2012 ).…”

Deletion of the type IV secretion system promoter VirB in Brucella abortus A19 strain attenuated the virulence of the bacteria and promotes autophagy

“…The viability of A19ΔvirB and parental strain A19 was assessed in Murine macrophage RAW264.7 and Murine dendritic cell sarcoma (DCS), as previously described (Zhang et al 2020). Briefly, macrophages and dendritic cells of 1×10 6 cells/well were inoculated into 6-well plates for 24 h in a cell culture incubator containing 5% CO2 at 37° C and then infected with brucella abortus A19 and mutated brucella abortus A19 at a multiplicity of infection (MOI) of 100:1.…”

“…However, the detection of antibodies in mouse serum was carried out by the method described by Zhang (Zhang et al 2020), and the Recombinant VirB1, VirB5, VirB8 and L7/L12 were used as detection proteins, and antibodies against VirB1, VirB5, VirB8 and L7/L12 were detected by Western blot.…”