Molecular Microbiology Research 2024, Vol.14, No.5, 236-247 http://microbescipublisher.com/index.php/mmr 240 compositions in the rhizosphere and endosphere compartments (Santos-Medellín et al., 2017). Previous studies have shown that the diversity index of rhizosphere soil bacterial community did not change significantly under drought stress, and the composition of rhizosphere soil bacterial community was different under drought stress and normal irrigation. Furthermore, through the analysis of bacterial community structure and species differences, it is found that drought stress significantly affected the structure and composition of bacterial community in rice rhizosphere soil. The change of bacterial community structure in rice rhizosphere soil may be a positive response of the rice-rhizosphere soil bacterial community to drought stress. Similarly, the microbial community structure in the rhizosphere of rice plants is influenced by the plant's growth stage and the specific soil environment, with certain bacterial phyla such as Gemmatimonadetes, Proteobacteria, and Verrucomicrobia being particularly affected (Breidenbach et al., 2016). 3.2 Functional roles of rhizosphere microbes in plant health Rhizosphere microbes are essential for enhancing plant growth and stress tolerance through various mechanisms. The edge of the plant root system is enriched with many rhizosphere microorganisms, which act as decomposers to transform the organic matter in the soil into inorganic matter that can be absorbed by plants, and at the same time, soil rhizosphere microorganisms secrete some plant hormones in the process of metabolism to provide necessary energy and hormones for the growth of plants, and finally achieve the role of promoting plant growth. Plant rhizosphere growth promoters can also stimulate plants to synthesize a variety of osmotic regulators such as proline, etc., to maintain cell osmotic balance, prevent cell dehydration, enhance antioxidant enzyme activity, help plants remove excess reactive oxygen species and other harmful substances, reduce oxidative damage, and thus improve plant drought tolerance. These microbes can improve nutrient uptake, promote plant growth, and protect plants from pathogens. For example, specific bacterial and fungal taxa such as Bacillus, Pseudomonas, Aspergillus, and Rhizopus have been associated with phosphorus solubilization and plant growth promotion in aluminum-tolerant rice genotypes (Xiao et al., 2022). PGPR inoculants indirectly promote plant growth and health by altering the composition and function of the rhizosphere microbial community (Kong et al., 2020; Hakim et al., 2021). Additionally, the presence of AMF in the rhizosphere has been shown to enhance plant tolerance to heavy metal stress by altering the microbial community structure and promoting the enrichment of beneficial microbes (Hao et al., 2021). Furthermore, the interactions between roots, rhizosphere, and rhizobacteria are critical for improving plant growth and tolerance to abiotic stresses such as drought, salinity, and heavy metals (Khan et al., 2021). 3.3 Impact of environmental factors on rhizosphere microbial communities Environmental factors such as soil type, salinity and drought significantly affected the composition and function of rhizosphere microbial communities. Soil pH, heavy metals, soil texture and nitrogen are the most important factors affecting rhizosphere microbial communities, and they play different roles in different fields (Deng et al., 2017; 2022). Under drought stress, plants affect the community structure and function of rhizosphere microorganisms by changing the type and quantity of their own root exudates. Drought stress induced changes in the main components of rhizosphere and endophytic microbial communities. Drought increases soil heterogeneity, restricts nutrient flow and access, and often leads to dramatic reductions in bacterial biomass. The changes in root exudates affected the diversity, richness and structure of microbial communities, and recruited and enriched plant rhizosphere growth-promoting bacteria. Rhizosphere microorganisms affect the growth and development of plants by interacting with them. The composition of endogenous bacterial communities in the roots of sensitive rice is significantly changed under drought stress, but the community composition of endophytic bacteria in the roots of early-tolerant rice is similar under normal irrigation and drought stress. The enrichment of drought-responsive microorganisms may be beneficial to plants by enhancing their drought resistance (Santos-Medellín et al., 2017). Similarly, saline-alkali stress affects rhizosphere microbial communities, and specialized microbial communities from specific environments enhance plant tolerance to salinity by promoting plant growth and shaping microbial community composition (Santos et al., 2021). In addition, soil salinization has also been shown to affect
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