Institute of Medical Microbiology, University of Zürich, Zürich, Switzerland.
mBio. 2024 Jun 12;15(6):e0071024. doi: 10.1128/mbio.00710-24. Epub 2024 Apr 29.
The causative agent of Legionnaires' disease, , is an environmental bacterium, that replicates in macrophages, parasitizes amoeba, and forms biofilms. employs the quorum sensing (Lqs) system and the transcription factor LvbR to control various bacterial traits, including virulence and biofilm architecture. LvbR negatively regulates the nitric oxide (NO) receptor Hnox1, linking quorum sensing to NO signaling. Here, we assessed the response of to NO and investigated bacterial receptors underlying this process. Chemical NO donors, such as dipropylenetriamine (DPTA) NONOate and sodium nitroprusside (SNP), delayed and reduced the expression of the promoters for flagellin (P) and the 6S small regulatory RNA (P). Marker-less mutant strains lacking individual (Hnox1, Hnox2, or NosP) or all three NO receptors (triple knockout, TKO) grew like the parental strain in media. However, in the TKO strain, the reduction of P expression by DPTA NONOate was less pronounced, suggesting that the NO receptors are implicated in NO signaling. In the Δ mutant, the promoter was upregulated, indicating that NosP negatively regulates LvbR. The single and triple NO receptor mutant strains were impaired for growth in phagocytes, and phenotypic heterogeneity of non-growing/growing bacteria in amoebae was regulated by the NO receptors. The single NO receptor and TKO mutant strains showed altered biofilm architecture and lack of response of biofilms to NO. In summary, we provide evidence that regulates virulence, intracellular phenotypic heterogeneity, and biofilm formation through NO and three functionally non-redundant NO receptors, Hnox1, Hnox2, and NosP.
The highly reactive diatomic gas molecule nitric oxide (NO) is produced by eukaryotes and bacteria to promote short-range and transient signaling within and between neighboring cells. Despite its importance as an inter-kingdom and intra-bacterial signaling molecule, the bacterial response and the underlying components of the signaling pathways are poorly characterized. The environmental bacterium forms biofilms and replicates in protozoan and mammalian phagocytes. harbors three putative NO receptors, one of which crosstalks with the quorum sensing (Lqs)-LvbR network to regulate various bacterial traits, including virulence and biofilm architecture. In this study, we used pharmacological, genetic, and cell biological approaches to assess the response of to NO and to demonstrate that the putative NO receptors are implicated in NO detection, bacterial replication in phagocytes, intracellular phenotypic heterogeneity, and biofilm formation.
军团病的病原体 ，是一种环境细菌，它在巨噬细胞中复制，寄生在变形虫上，并形成生物膜。利用群体感应（Lqs）系统和转录因子 LvbR 来控制各种细菌特性，包括毒力和生物膜结构。LvbR 负调控一氧化氮（NO）受体 Hnox1，将群体感应与 NO 信号联系起来。在这里，我们评估了 对 NO 的反应，并研究了这一过程中的细菌受体。化学 NO 供体，如二丙三胺（DPTA）NONOate 和硝普钠（SNP），延迟和降低了鞭毛（P）和 6S 小调节 RNA（P）启动子的表达。标记缺失的突变株缺乏单个（Hnox1、Hnox2 或 NosP）或所有三个 NO 受体（三缺失突变株，TKO）在培养基中像亲本菌株一样生长。然而，在 TKO 菌株中，DPTA NONOate 对 P 表达的减少不明显，表明 NO 受体参与了 NO 信号。在Δ突变体中，P 启动子上调，表明 NosP 负调控 LvbR。单和三缺失突变株在吞噬细胞中的生长受到损害，非生长/生长变形虫中的细菌表型异质性受 NO 受体调节。单 NO 受体和 TKO 突变株表现出改变的生物膜结构和生物膜对 NO 无反应。总之，我们提供的证据表明，通过 NO 和三个功能上非冗余的 NO 受体（Hnox1、Hnox2 和 NosP）， 调节毒力、细胞内表型异质性和生物膜形成。
作为一种具有高反应性的双原子气体分子，一氧化氮（NO）由真核生物和细菌产生，以促进细胞内和细胞间的短程和瞬时信号传递。尽管作为一种种间和种内信号分子非常重要，但细菌的反应及其信号通路的潜在成分仍知之甚少。环境细菌 形成生物膜并在原生动物和哺乳动物吞噬细胞中复制。 含有三个假定的 NO 受体，其中一个与群体感应（Lqs）-LvbR 网络相互作用，以调节各种细菌特性，包括毒力和生物膜结构。在这项研究中，我们使用药理学、遗传学和细胞生物学方法来评估 对 NO 的反应，并证明假定的 NO 受体参与了 NO 的检测、吞噬细胞中的细菌复制、细胞内表型异质性和生物膜形成。
