Molecular Microbiology Research 2024, Vol.14, No.5, 218-225 http://microbescipublisher.com/index.php/mmr 219 2 Rhizosphere Microbes: Diversity and Functions 2.1 Types of rhizosphere microbes The rhizosphere, the narrow region of soil influenced by root secretions and associated soil microorganisms, hosts a diverse array of microbes including bacteria, fungi, and actinomycetes. These microbial communities play crucial roles in plant health and soil fertility. Rhizosphere bacteria are highly diverse and include beneficial genera such as Pseudomonas, Rhizobium, and Bacillus. These bacteria can promote plant growth by fixing nitrogen, solubilizing phosphorus, and producing plant growth-promoting hormones (Wu et al., 2021). They can act as biocontrol agents against soil-borne pathogens. Mycorrhizal fungi, particularly arbuscular mycorrhizal (AM) fungi, form symbiotic relationships with plant roots, enhancing nutrient uptake, especially phosphorus and nitrogen, and improving plant stress tolerance (Shi et al., 2022). These fungi also play a role in structuring the rhizosphere microbiome, which can further influence plant health and stress resistance (Figure 1) (Hao et al., 2021). These filamentous bacteria are known for their ability to decompose complex organic materials and produce antibiotics that suppress soil pathogens. Genera such as Streptomyces and Arthrobacter are commonly found in the rhizosphere and contribute to plant health by promoting nutrient cycling and inhibiting harmful microbes. The study by Hao et al. (2021) demonstrated that arbuscular mycorrhizal fungi promote tolerance to the harmful heavy metal lanthanum by regulating the structure of the rhizosphere microbial community. They help plants cope better with adverse environments by enhancing nutrient absorption and inducing the enrichment of beneficial microorganisms. Figure 1 PCoA of unweighted UniFrac distances for the rhizosphere bacteria (a) and fungi (b) of different treatments on OTUs level. Co-occurrence network analysis for the rhizosphere bacteria (c) and fungi (d) of different treatments on OTUs level with abundance more than 50 (Adopted from Hao et al., 2021)
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