Molecular Pathogens, 2025, Vol.16, No.5, 246-256 http://microbescipublisher.com/index.php/mp 252 slime) themselves have a long turnover period and can directly contribute to soil organic matter (Agnihotri et al., 2021). The use of exudates by rhizosphere microorganisms will produce a biological carbon sink effect, and arbuscular mycorrhizal fungi can build part of the host plant carbon into mycelium. The mycelial wall is difficult to degrade and can be regarded as a kind of carbon stabilization (Mason et al., 2025). Symbiosis between wheat and mycorrhizae can increase soil fungal source carbon, which is also one of the forms of carbon fixation. Figure 1 Scanning electron microscopy (SEM) micrographs (Adopted from Sharma et al., 2020) Image caption: (A) Biofilm formation by B26 on glass surface (Bar = 30μm). (B) Control Brachypodium distachyon Bd21-3 roots (Bar = 300 μm). (C) Biofilm formation by B26 on the surface of roots prior to root exudate collection of Bd21-3 (Bar = 50μm). (D) Magnified view of biofilm formed by B26 on Bd21-3 roots after root exudate collection (Bar = 20 μm) (Adopted from Sharma et al., 2020) 7.2 Improvement of soil structure and enzyme activity Wheat root exudates play an important role in improving soil structure and increasing soil biological activity. The sticky polysaccharide secreted by it is a key cementing agent for the formation of soil aggregates, which can combine small particles into large aggregates, improve porosity and aeration, alleviate soil compaction, and provide a stable environment for root growth and microbial colonization (Rahim et al., 2020). At the same time, the carbon source secreted by the roots promotes the reproduction of microorganisms, enhances the activity of soil enzymes, such as cellulase, sucrase and acid phosphatase, and accelerates the decomposition of organic matter and nutrient recycling. Signaling substances such as amino acids released by the roots can also activate dormant microorganisms and further increase enzyme levels. Long-term wheat cultivation can maintain high enzyme activity and soil fertility (Paz-Vidal et al., 2023; Bardelli et al., 2024). The improvement of soil structure and enzyme activity promote each other, forming a virtuous cycle with root exudates as the core. Wheat root exudates can be called natural "soil conditioners", and their rational utilization (such as diversified crop rotation) can effectively improve the stability of soil structure and ecological vitality, and achieve sustainable development of cultivated land quality. 7.3 Case study: effect of root exudates on microbial homeostasis in long-term wheat cultivation system In order to deeply understand the role of root exudates in maintaining soil microbial homeostasis, we took the long-term wheat monoculture system as an example for analysis. Under the conditions of long-term continuous wheat cultivation, a specific microbial community structure compatible with wheat root exudates will be formed in the soil. This community shows certain steady-state characteristics to external interference. Long-term wheat fields often experience accumulation of soil-borne pathogens or soil fatigue, and disease-suppressive soils may also develop. Root exudates are one of the driving factors behind these phenomena. Specifically, in the early stages of continuous wheat cropping, a large amount of root exudates enter the soil. Due to the lack of diversity, some obligate carbon-consuming bacteria multiply rapidly, resulting in a competitive disadvantage for beneficial bacteria, a reduction in microbial diversity, and a "disease-inducing" transformation of the soil. As the continuous
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