Table_2_Quorum Sensing System Affects the Plant Growth Promotion Traits of Serratia fonticola GS2.DOCX

Quorum sensing (QS) enables bacteria to organize gene expression programs, thereby coordinating collective behaviors. It involves the production, release, and population-wide detection of extracellular signaling molecules. The cellular processes regulated by QS in bacteria are diverse and may be used in mutualistic coordination or in response to changing environmental conditions. Here, we focused on the influence of the QS-dependent genes of our model bacterial strain Serratia fonticola GS2 on potential plant growth promoting (PGP) activities including indole-3-acetic acid (IAA) production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, and biofilm formation. Based on genomic and phenotypic experimental data we identified and investigated the function of QS genes in the genome of the model strain. Our gene deletion study confirmed the biological functionality of the QS auto-inducer (gloI) and receptor (gloR) on potential PGP activities of GS2. A transcriptomic approach was also undertaken to understand the role of QS genes in regulation of genes primarily involved in PGP activities (IAA, ACC deaminase activity, and biofilm formation). Both transcriptomic and phenotypic data revealed that the QS-deletion mutants had considerably less PGP activities, as compared to the wild type. In addition, in vivo plant experiments showed that plants treated with GS2 had significantly higher growth rates than plants treated with the QS-deletion mutants. Overall, our results showed how QS-dependent genes regulate the potential PGP activities of GS2. This information may be helpful in understanding the relationship between QS-dependent genes and the PGP activity of bacteria, which aid in the production of practical bio-fertilizers for plant growth promotion.

群体感应（Quorum sensing, QS）可使细菌有序调控基因表达程序，进而协调群体行为。该过程涉及胞外信号分子的产生、释放及群体水平检测。细菌中受QS调控的细胞过程多样，可用于互利协调或响应多变的环境条件。本研究聚焦于模式菌株食泉沙雷氏菌（Serratia fonticola）GS2的QS依赖型基因对其潜在植物促生（plant growth promoting, PGP）活性的影响，具体包括吲哚-3-乙酸（indole-3-acetic acid, IAA）合成、1-氨基环丙烷-1-羧酸（1-aminocyclopropane-1-carboxylate, ACC）脱氨酶活性及生物膜形成能力。研究人员基于基因组与表型实验数据，对该模式菌株基因组中的QS基因功能进行了鉴定与分析。基因敲除实验证实，QS自诱导剂（gloI）与受体（gloR）对GS2的潜在PGP活性具有生物学调控功能。本研究还采用转录组学方法，解析了QS基因对主要参与PGP活性（IAA合成、ACC脱氨酶活性及生物膜形成）的基因的调控作用。转录组与表型数据均显示，与野生型菌株相比，QS敲除突变体的PGP活性显著降低。此外，体内植物实验表明，经GS2处理的植株生长速率显著高于经QS敲除突变体处理的植株。综上，本研究阐明了QS依赖型基因对GS2潜在PGP活性的调控机制。相关结果有助于理解QS依赖型基因与细菌PGP活性之间的关联，可为开发用于植物促生的实用型生物肥料提供理论支撑。