Molecular Microbiology Research 2024, Vol.14, No.5, 248-258 http://microbescipublisher.com/index.php/mmr 250 nitrogen-deficient soils. These bacteria colonize the rhizosphere and form nodules on plant roots, where they fix nitrogen in exchange for carbon compounds from the plant. This process not only enhances plant growth but also reduces the need for chemical nitrogen fertilizers, promoting sustainable agricultural practices (Kumar et al., 2022). 3.1.3 Plant growth-promoting rhizobacteria (PGPR) PGPR (Plant Growth-Promoting Rhizobacteria) are a diverse group of bacteria that promote plant growth through various mechanisms, including nutrient solubilization, hormone production, and disease suppression. PGPR-mediated rhizosphere engineering directly and indirectly enhances plant growth (Figure 1). For instance, Bacillus, Pseudomonas, and Burkholderia are known to produce indole-3-acetic acid (IAA), solubilize phosphates, and produce siderophores, thereby improving nutrient availability and uptake (Erturk et al., 2010; Liu et al., 2020; Hakim et al., 2021). These bacteria can also induce systemic resistance in plants, helping them to withstand both biotic and abiotic stresses (Khan et al., 2021; Qiuping et al., 2021). Figure 1 illustrates in detail how PGPR promotes plant growth through various mechanisms. PGPR is a diverse group of bacteria that support healthy plant growth by solubilizing nutrients (such as phosphate and potassium), producing hormones (such as auxins and cytokinins), and suppressing diseases (through biocontrol agents and induced systemic resistance). These mechanisms work together to significantly enhance nutrient uptake and disease resistance, thereby improving crop growth and yield. Figure 1 The benefits of PGPR-mediated rhizosphere engineering to the plant growth (Adopted from Hakim et al., 2021) 3.2 Antagonistic interactions Antagonistic interactions in the rhizosphere involve competition, antibiosis, and parasitism among microbial communities. These interactions can suppress plant pathogens and enhance plant health. For example, organic amendments have been shown to increase the abundance of beneficial bacteria while reducing pathogenic fungi like Fusarium in the kiwifruit rhizosphere. PGPR can also produce antibiotics and lytic enzymes that inhibit the growth of phytopathogens, thereby protecting plants from diseases (Hakim et al., 2021; Kong and Liu, 2022).
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