Dipartimento di Biologia e Biotecnologie, Università degli Studi di Pavia, Pavia, Italy.
PLoS One. 2013;8(1):e55112. doi: 10.1371/journal.pone.0055112. Epub 2013 Jan 28.
Many putative virulence factors of Burkholderia cenocepacia are controlled by various quorum sensing (QS) circuits. These QS systems either use N-acyl homoserine lactones (AHL) or cis-2-dodecenoic acid ("Burkholderia diffusible signal factor", BDSF) as signalling molecules. Previous work suggested that there is little cross-talk between both types of systems. We constructed mutants in B. cenocepacia strain J2315, in which genes encoding CepI (BCAM1870), CciI (BCAM0239a) and the BDSF synthase (BCAM0581) were inactivated, and also constructed double (ΔcepIΔBCAM0581, ΔcciIΔBCAM0581 and ΔcepIΔcciI) mutants and a triple (ΔcepIΔcciIΔBCAM0581) mutant. Subsequently we investigated phenotypic properties (antibiotic susceptibility, biofilm formation, production of AHL and BDSF, protease activity and virulence in Caenorhabditis elegans) and measured gene expression in these mutants, and this in the presence and absence of added BDSF, AHL or both. The triple mutant was significantly more affected in biofilm formation, antimicrobial susceptibility, virulence in C. elegans, and protease production than either the single or double mutants. The ΔBCAM0581 mutant and the ΔcepIΔBCAM0581 and ΔcciIΔBCAM0581 double mutants produced significantly less AHL compared to the WT strain and the ΔcepI and ΔcciI single mutant, respectively. The expression of cepI and cciI in ΔBCAM0581, was approximately 3-fold and 7-fold (p<0.05) lower than in the WT, respectively. The observed differences in AHL production, expression of cepI and cciI and QS-controlled phenotypes in the ΔBCAM0581 mutant could (at least partially) be restored by addition of BDSF. Our data suggest that, in B. cenocepacia J2315, AHL and BDSF-based QS systems co-regulate the same set of genes, regulate different sets of genes that are involved in the same phenotypes and/or that the BDSF system controls the AHL-based QS system. As the expression of the gene encoding the C6-HSL synthase CciI (and to a lesser extent the C8-HSL synthase CepI) is partially controlled by BDSF, it seems likely that the BDSF QS systems controls AHL production through this system.
许多洋葱伯克霍尔德菌的假定毒力因子受各种群体感应（QS）回路控制。这些 QS 系统要么使用 N-酰基高丝氨酸内酯（AHL），要么使用顺-2-十二烯酸（“伯克霍尔德氏扩散信号因子”，BDSF）作为信号分子。以前的工作表明，这两种系统之间几乎没有交叉对话。我们构建了洋葱伯克霍尔德菌 J2315 菌株的突变体，其中编码 CepI（BCAM1870）、CciI（BCAM0239a）和 BDSF 合酶（BCAM0581）的基因失活，还构建了双（ΔcepIΔBCAM0581、ΔcciIΔBCAM0581 和 ΔcepIΔcciI）突变体和三（ΔcepIΔcciIΔBCAM0581）突变体。随后，我们研究了这些突变体的表型特性（抗生素敏感性、生物膜形成、AHL 和 BDSF 的产生、蛋白酶活性和秀丽隐杆线虫中的毒力），并测量了这些突变体在添加 BDSF、AHL 或两者的情况下的基因表达。与单突变体或双突变体相比，三突变体在生物膜形成、抗微生物敏感性、秀丽隐杆线虫中的毒力和蛋白酶产生方面受到的影响更为显著。与 WT 菌株和ΔcepI 和ΔcciI 单突变体相比，ΔBCAM0581 突变体和ΔcepIΔBCAM0581 和ΔcciIΔBCAM0581 双突变体分别产生的 AHL 显著减少。在ΔBCAM0581 中，cepI 和 cciI 的表达分别比 WT 低约 3 倍和 7 倍（p<0.05）。在ΔBCAM0581 突变体中观察到的 AHL 产生、cepI 和 cciI 表达以及 QS 控制表型的差异至少部分可以通过添加 BDSF 来恢复。我们的数据表明，在洋葱伯克霍尔德菌 J2315 中，AHL 和 BDSF 为基础的 QS 系统共同调节相同的一组基因，调节不同的一组基因，这些基因参与相同的表型，或者 BDSF 系统控制 AHL 为基础的 QS 系统。由于 C6-HSL 合酶 CciI（和较小程度的 C8-HSL 合酶 CepI）的基因表达部分受 BDSF 控制，因此 BDSF QS 系统似乎通过该系统控制 AHL 的产生。
