Jiangsu Provincial Key Lab for Organic Solid Waste Utilization, National Engineering Research Center for Organic-Based Fertilizers, Jiangsu Collaborative Innovation Center for Solid Organic Waste Resource Utilization, Nanjing Agricultural University, Nanjing, People's Republic of China.
Key Laboratory of Microbial Resources Collection and Preservation, Ministry of Agriculture, Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China.
Appl Environ Microbiol. 2018 Apr 2;84(8). doi: 10.1128/AEM.02744-17. Print 2018 Apr 15.
Efficient biofilm formation and root colonization capabilities facilitate the ability of beneficial plant rhizobacteria to promote plant growth and antagonize soilborne pathogens. Biofilm formation by plant-beneficial strains is triggered by environmental cues, including oxygen deficiency, but the pathways that sense these environmental signals and regulate biofilm formation have not been thoroughly elucidated. In this study, we showed that the ResDE two-component regulatory system in the plant growth-promoting rhizobacterium strain SQR9 senses the oxygen deficiency signal and regulates biofilm formation. ResE is activated by sensing the oxygen limitation-induced reduction of the NAD/NADH pool through its PAS domain, stimulating its kinase activity, and resulting in the transfer of a phosphoryl group to ResD. The phosphorylated ResD directly binds to the promoter regions of the and operons to improve the biosynthesis of terminal oxidases, which can interact with KinB to activate biofilm formation. These results not only revealed the novel regulatory function of the ResDE two-component system but also contributed to the understanding of the complicated regulatory network governing biofilm formation. This research may help to enhance the root colonization and the plant-beneficial efficiency of SQR9 and other rhizobacteria used in agriculture. spp. are widely used as bioinoculants for plant growth promotion and disease suppression. The exertion of their plant-beneficial functions is largely dependent on their root colonization, which is closely related to their biofilm formation capabilities. On the other hand, is the model bacterium for biofilm study, and the process and molecular network of biofilm formation are well characterized (B. Mielich-Süss and D. Lopez, Environ Microbiol 17:555-565, 2015, https://doi.org/10.1111/1462-2920.12527; L. S. Cairns, L. Hobley, and N. R. Stanley-Wall, Mol Microbiol 93:587-598, 2014, https://doi.org/10.1111/mmi.12697; H. Vlamakis, C. Aguilar, R. Losick, and R. Kolter, Genes Dev 22:945-953, 2008, https://doi.org/10.1101/gad.1645008; S. S. Branda, A. Vik, L. Friedman, and R. Kolter, Trends Microbiol 13:20-26, 2005, https://doi.org/10.1016/j.tim.2004.11.006; C. Aguilar, H. Vlamakis, R. Losick, and R. Kolter, Curr Opin Microbiol 10:638-643, 2007, https://doi.org/10.1016/j.mib.2007.09.006; S. S. Branda, J. E. González-Pastor, S. Ben-Yehuda, R. Losick, and R. Kolter, Proc Natl Acad Sci U S A 98:11621-11626, 2001, https://doi.org/10.1073/pnas.191384198). However, the identification and sensing of environmental signals triggering biofilm formation need further research. Here, we report that the oxygen deficiency signal inducing biofilm formation is sensed by the ResDE two-component regulatory system. Our results not only revealed the novel regulatory function of the ResDE two-component regulatory system but also identified the sensing system of a biofilm-triggering signal. This knowledge can help to enhance the biofilm formation and root colonization of plant-beneficial strains and also provide new insights of bacterial biofilm formation regulation.
生物膜的形成和根定植能力有助于有益植物根际细菌促进植物生长和拮抗土传病原菌的能力。有益植物菌株的生物膜形成是由环境信号触发的，包括缺氧，但感知这些环境信号并调节生物膜形成的途径尚未得到彻底阐明。在本研究中，我们表明，植物促生菌 SQR9 中的 ResDE 双组分调节系统感知缺氧信号并调节生物膜形成。ResE 通过其 PAS 结构域感知由缺氧诱导的 NAD/NADH 池减少来激活，刺激其激酶活性，并导致磷酸基团转移到 ResD。磷酸化的 ResD 直接与 和 操纵子的启动子区域结合，以改善末端氧化酶的生物合成，这可以与 KinB 相互作用激活生物膜形成。这些结果不仅揭示了 ResDE 双组分系统的新调节功能，而且有助于理解调控生物膜形成的复杂调节网络。这项研究可能有助于提高 SQR9 和其他用于农业的 根际细菌的根定植和植物有益效率。 spp. 被广泛用作促进植物生长和抑制疾病的生物接种剂。它们发挥植物有益功能在很大程度上取决于它们的根定植，这与它们的生物膜形成能力密切相关。另一方面， 是生物膜研究的模式细菌，生物膜形成的过程和分子网络得到了很好的描述（B. Mielich-Süss 和 D. Lopez，Environ Microbiol 17:555-565, 2015, https://doi.org/10.1111/1462-2920.12527; L. S. Cairns, L. Hobley 和 N. R. Stanley-Wall，Mol Microbiol 93:587-598, 2014, https://doi.org/10.1111/mmi.12697; H. Vlamakis, C. Aguilar, R. Losick 和 R. Kolter，Genes Dev 22:945-953, 2008, https://doi.org/10.1101/gad.1645008; S. S. Branda, A. Vik, L. Friedman 和 R. Kolter，Trends Microbiol 13:20-26, 2005, https://doi.org/10.1016/j.tim.2004.11.006; C. Aguilar, H. Vlamakis, R. Losick 和 R. Kolter，Curr Opin Microbiol 10:638-643, 2007, https://doi.org/10.1016/j.mib.2007.09.006; S. S. Branda, J. E. González-Pastor, S. Ben-Yehuda, R. Losick 和 R. Kolter，Proc Natl Acad Sci U S A 98:11621-11626, 2001, https://doi.org/10.1073/pnas.191384198）。然而，触发生物膜形成的环境信号的识别和感知需要进一步研究。在这里，我们报告说，诱导生物膜形成的缺氧信号是由 ResDE 双组分调节系统感知的。我们的结果不仅揭示了 ResDE 双组分调节系统的新调节功能，而且确定了生物膜触发信号的感应系统。这方面的知识有助于增强有益植物 菌株的生物膜形成和根定植能力，也为细菌生物膜形成调控提供了新的见解。
