URBM, Department of Biology, University of Namur, Namur, Belgium.
PLoS One. 2013 Dec 11;8(12):e82514. doi: 10.1371/journal.pone.0082514. eCollection 2013.
Brucella quorum sensing has been described as an important regulatory system controlling crucial virulence determinants such as the VirB type IV secretion system and the flagellar genes. However, the basis of quorum sensing, namely the production of autoinducers in Brucella has been questioned. Here, we report data obtained from the use of a genetic tool allowing the in situ detection of long-chain N-acyl-homoserine lactones (AHL) activity at single bacterium level in Brucella melitensis. These data are consistent with an intrinsic production of AHL by B. melitensis in low concentration both during in vitro growth and macrophage infection. Moreover, we identified a protein, named AibP, which is homologous to the AHL-acylases of various bacterial species. In vitro and during infection, expression of aibP coincided with a decrease in endogenous AHL activity within B. melitensis, suggesting that AibP could efficiently impair AHL accumulation. Furthermore, we showed that deletion of aibP in B. melitensis resulted in enhanced virB genes expression and VirB8 production as well as in a reduced flagellar genes expression and production of FlgE (hook protein) and FliC (flagellin) in vitro. Altogether, these results suggest that AHL-dependent quorum sensing and AHL-quorum quenching coexist in Brucella, at least to regulate its virulence.
布鲁氏菌群体感应被描述为一种重要的调控系统，控制着关键的毒力决定因素，如 VirB 型 IV 型分泌系统和鞭毛基因。然而，群体感应的基础，即布鲁氏菌中自动诱导物的产生一直存在争议。在这里，我们报告了使用一种遗传工具获得的数据，该工具允许在布鲁氏菌中单个细菌水平原位检测长链 N-酰基高丝氨酸内酯 (AHL) 活性。这些数据与布鲁氏菌在体外生长和巨噬细胞感染过程中以低浓度固有产生 AHL 的情况一致。此外，我们鉴定了一种名为 AibP 的蛋白，它与各种细菌的 AHL 酰基酶同源。在体外和感染过程中，aibP 的表达与布鲁氏菌内内源 AHL 活性的降低相一致，表明 AibP 可以有效地抑制 AHL 的积累。此外，我们表明，在布鲁氏菌中缺失 aibP 会导致 virB 基因表达和 VirB8 产生增强，以及鞭毛基因表达和 FlgE（钩蛋白）和 FliC（鞭毛蛋白）的产生减少。总之，这些结果表明，至少在布鲁氏菌中，AHL 依赖性群体感应和 AHL 群体淬灭共存，以调节其毒力。
