An Osmoregulatory Mechanism Operating through OmpR and LrhA Controls the Motile-Sessile Switch in the Plant GrowthPromoting Bacterium Pantoea alhagi
An Osmoregulatory Mechanism Operating through OmpR and LrhA Controls the Motile-Sessile Switch in the Plant GrowthPromoting Bacterium Pantoea alhagi
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通过 OmpR 和 LrhA 运作的渗透调节机制控制植物生长促进细菌 Pantoea alhagi 中的运动-固着开关
DOI：
10.1128/aem.00077-19
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发表时间：
2019
影响因子：
4.4
通讯作者：
Zhang Lei
中科院分区：
文献类型：
--
作者：
Li Shuyu;Liang Hong;Wei Zhiyan;Bai Haonan;Li Mengyun;Li Qiqi;Qu Meng;Shen Xihui;Wang Yao;Zhang Lei
对渗透胁迫的适应对于细菌在不断变化的环境中的生长和生存至关重要。虽然已经在各种细菌中发现了大量的渗透胁迫反应基因，但渗透变化如何影响细菌的运动性、生物膜的形成和宿主生态位的定植在很大程度上仍不清楚。在本研究中，我们报道了LrhA调节因子是一种渗透调节转录因子，它直接与flhDC、EPS和opgGH操纵子的启动子结合，并对它们的表达进行差异调节，从而抑制植物生长促进细菌Pantoea alhagi LTYR-11z的运动和促进胞外多糖(EPS)的产生、渗透调节周质葡聚糖(OPGs)的合成、生物膜的形成和根的定植。此外，我们观察到，LrhA调节的OPGs以浓度依赖的方式控制RcsCD-RCSB的激活，并维持由介质渗透压增加诱导的高浓度OPGs，以实现RCS磷酸继电器的高水平激活，这导致Alhagi的EPS合成增强和运动性降低。此外，我们还发现渗透调节因子OmpR直接与hRHA的启动子结合并促进其表达，而rHA的表达受到激活的RCS磷酸传递系统的反馈抑制。总体而言，我们的数据支持这样一个模型，即P。通过EnvZ-OmpR双组分系统和LrhA来调节OPGs的合成、EPS的产生和鞭毛依赖的运动性，从而利用分级信号级联来控制移动生活方式和生物膜生活方式之间的转换，从而改变环境渗透压。许多移动细菌种群响应特定的环境线索，包括自然和寄主相关系统中的渗透胁迫，形成表面附着的生物膜。然而，细菌渗透感知、游泳和生物膜形成调控网络之间的相互作用还不完全清楚。在此，我们报道了泛藻中的多效性调节子LrhA参与鞭毛运动、生物膜形成和寄主定植的调节，并对渗透压上移做出反应。我们进一步证明，这种感觉依赖于EnvZ-OmpR双组分系统，该系统已知可以检测外部渗透胁迫的变化。EnvZ-OmpR-LRhA渗透信号转导通路被认为是为了提高细菌在宿主内高渗条件下的适合度。我们的工作提出了一种新的调控机制，将渗透感受和运动-固定的生活方式转变联系起来，这可能为防止或促进生物膜和宿主定植INP的形成提供新的途径。Alhagi和其他具有类似渗透调节机制的细菌。
Adaptation to osmotic stress is crucial for bacterial growth and survival in changing environments. Although a large number of osmotic stress response genes have been identified in various bacterial species, how osmotic changes affect bacterial motility, biofilm formation, and colonization of host niches remains largely unknown. In this study, we report that the LrhA regulator is an osmoregulated transcription factor that directly binds to the promoters of theflhDC,eps, andopgGHoperons and differentially regulates their expression, thus inhibiting motility and promoting exopolysaccharide (EPS) production, synthesis of osmoregulated periplasmic glucans (OPGs), biofilm formation, and root colonization of the plant growth-promoting bacterium Pantoea alhagi LTYR-11Z. Further, we observed that the LrhA-regulated OPGs control RcsCD-RcsB activation in a concentration-dependent manner, and a high concentration of OPGs induced by increased medium osmolarity is maintained to achieve the high level of activation of the Rcs phosphorelay, which results in enhanced EPS synthesis and decreased motility in P. alhagi. Moreover, we showed that the osmosensing regulator OmpR directly binds to the promoter oflrhAand promotes its expression, whilelrhAexpression is feedback inhibited by the activated Rcs phosphorelay system. Overall, our data support a model wherebyP. alhagisenses environmental osmolarity changes through the EnvZ-OmpR two-component system and LrhA to regulate the synthesis of OPGs, EPS production, and flagellum-dependent motility, thereby employing a hierarchical signaling cascade to control the transition between a motile lifestyle and a biofilm lifestyle.IMPORTANCEMany motile bacterial populations form surface-attached biofilms in response to specific environmental cues, including osmotic stress in a range of natural and host-related systems. However, cross talk between bacterial osmosensing, swimming, and biofilm formation regulatory networks is not fully understood. Here, we report that the pleiotropic regulator LrhA inPantoea alhagiis involved in the regulation of flagellar motility, biofilm formation, and host colonization and responds to osmotic upshift. We further show that this sensing relies on the EnvZ-OmpR two-component system that was known to detect changes in external osmotic stress. The EnvZ-OmpR-LrhA osmosensing signal transduction cascade is proposed to increase bacterial fitness under hyperosmotic conditions inside the host. Our work proposes a novel regulatory mechanism that links osmosensing and motile-sessile lifestyle transitions, which may provide new approaches to prevent or promote the formation of biofilms and host colonization inP. alhagiand other bacteria possessing a similar osmoregulatory mechanism.