To investigate the effects of Pseudomonas monteilii SX001 on various parameters of cucumber plants under salt stress, the salt-sensitive cucumber variety Jinyou No. 4 was used as the test material, and coconut bran was used to simulate salt stress by applying NaCl solution. The results indicated that salt stress significantly reduced the morphological structure, relative growth rate, root morphology, and photosynthetic parameters of the cucumber plants. Leaf starch, soluble sugar, and sucrose contents significantly increased, whereas their levels in roots decreased. Cell membrane damage leads to the accumulation of reactive oxygen species and malondialdehyde, with notable increases in the activities of major antioxidant enzymes such as SOD, CAT, and POD. Nitrogen metabolism was disrupted, as evidenced by a significant decrease in nitrate nitrogen content and an increase in ammonium nitrogen content, as well as a significant reduction in the activity of NR enzymes involved in nitrogen metabolism. The enzyme activity in the cucumber rhizosphere soil decreased. However, Pseudomonas monteilii SX001 significantly enhanced the growth of cucumber seedlings under salt stress, improved photosynthetic efficiency, and facilitated sugar transformation and transport via glucose metabolism. Additionally, Pseudomonas monteilii SX001 reduced the reactive oxygen content and increased antioxidant enzyme activity. It also increased the activity of substrate enzymes and decreased the diversity of rhizosphere soil microorganisms but also increased the abundance of Asticcacaulis, Acinetobacter, Brevundimonas, Pseudomonas, and Enterobacter. These findings demonstrate that Pseudomonas monteilii SX001 is a promising bioinoculant for alleviating salt stress in cucumber production and improving soil health.

Soil acts as a crucial reservoir for both nutrients and microorganisms, hosting a wide range of microbial communities essential for ecosystem health. Particularly noteworthy are the interactions between plants and these microbes in the rhizosphere, as they actively contribute to sustaining plant well-being and fortifying plants against environmental pressures. Challenges, such as drought and salinity, pose significant threats to agricultural output and overall plant development. Therefore, it is imperative to explore the intricate mechanisms of stress responses to develop strategies to bolster plant resilience. Plant growth-promoting rhizobacteria (PGPR) offer a promising avenue for alleviating stress-induced damage in plants. Recent progress in the understanding of drought stress has shed light on the physiological and biochemical reactions within plants, emphasizing the critical role of abscisic acid (ABA) in stress mitigation. Similarly, advancements in research on salinity tolerance have elucidated the functions of ion transporters and stress signaling proteins. PGPRs play a crucial role in enhancing plant stress resilience through various mechanisms, including the regulation of ethylene levels, enhancement of nutrient absorption, and synthesis of hormones and enzymes. Utilizing the synergistic potential of plant-microbial interactions presents a promising strategy for tackling salinity and drought challenges in agriculture. Furthermore, PGPRs are instrumental in mitigating the effects of organic pollutants and heavy metals via mechanisms such as ACC deaminase activity. Innovative approaches, such as constructed wetland systems, leverage plant-microbial interactions to enhance water quality by purging pollutants.