Endophytic bacteria have been explored for their role in plant growth promotion, however, not much has been explored in cucumber. The metabolomic response of plants to application of such microbes also remains largely unknown. Thus, we investigated the application of endophytic bacteria to cucumber to infer their role in plant growth promotion and document metabolome response. The lowest healthy leaf-stalks were sampled from four differently sourced cucumber plants, and endophytic bacteria were isolated after surface disinfection. Initial plant growth-promoting (PGP) screening was performed to identify PGP strains out of numerous isolates, and five strains (Strains 4=Curtobacterium spp., 72=Brevibacillus spp., 167=Paenibacillus spp., 193=Bacillus spp., and 227=Microbacterium spp.) were selected based on their contribution to root growth compared with the control. The selected strains were further evaluated in pot experiments, axenic PGP trait assays, and metabolomic analysis. Results revealed that the selected isolates possessed different qualitative characteristics among indole acetic acid, siderophore production, phosphate solubilization, and 1-aminocyclopropane-1-carboxylate (ACC)-deaminase and nifH genes, and all isolates significantly enhanced plant growth in both pot experiments compared with the uninoculated control and fertilizer control. Metabolomic profiling revealed that both strains affected the plant metabolomes compared with the uninoculated control. Around 50 % of the metabolites explored had higher concentrations in either or both bacteria-applied plants compared with the uninoculated control. Differences were observed in both strains’ regulation of metabolites, although both enhanced root growth near equally. Overall, endophytic bacteria significantly enhanced plant growth and tended to produce or induce release of certain metabolites within the plant endosphere.

人们已经探索了内生细菌在植物生长促进中的作用，但是，在黄瓜中却没有太多探索。植物对此类微生物的代谢反应也仍然很大程度上未知。因此，我们研究了内生细菌在黄瓜中的应用，以推断它们在植物生长促进中的作用并记录代谢组反应。从四种不同来源的黄瓜植株中采集最低健康叶柄，表面消毒后分离内生细菌。进行初始植物生长促进 (PGP) 筛选，从众多分离株中鉴定出 PGP 菌株，共 5 株（菌株 4 =库氏杆菌属、72 =短芽孢杆菌属、167 =类芽孢杆菌属、193 =芽孢杆菌属、以及227 =微杆菌属 (Microbacter spp.) 根据其与对照相比对根生长的贡献进行选择。所选菌株在盆栽实验、无菌 PGP 性状测定和代谢组学分析中进行了进一步评估。结果显示，所选分离株在吲哚乙酸、铁载体产生、磷酸盐溶解、1-氨基环丙烷-1-羧酸酯（ACC）-脱氨酶和nif H基因方面具有不同的质量特征，并且所有分离株在两个盆栽实验中均显着增强了植物生长与未接种对照和施肥对照相比。代谢组学分析显示，与未接种的对照相比，两种菌株均影响植物代谢组。与未接种的对照相比，大约 50% 的探索代谢物在任一或两个施用细菌的植物中浓度较高。 尽管两种菌株对根系生长的促进作用几乎相同，但两种菌株对代谢物的调节存在差异。总体而言，内生细菌显着促进植物生长，并倾向于在植物内圈内产生或诱导释放某些代谢物。