Genomics and Applied Biology 2024, Vol.15, No.5, 255-263 http://bioscipublisher.com/index.php/gab 257 are involved in iron oxidation. The heading stage sees a peak in methanogenic archaea and methanotrophic bacteria, driven by the increased availability of root exudates and changes in soil redox conditions (Schmidt and Eickhorst, 2013). Finally, during the maturation stage, the microbial community stabilizes, with a notable presence of bacteria involved in nitrogen and carbon cycling (Figure 1) (Wang et al., 2019; Liu et al., 2023; Tang, 2024). 3.3 General trends in rhizosphere microbial community structure across seasonal stages Throughout the growing season, the microbial community in the rice rhizosphere undergoes significant changes. Initially, the microbial diversity is relatively low but increases as the plant grows and root exudates become more complex. The rhizosphere effect, where the microbial community in the rhizosphere is distinct from that in the bulk soil, is evident across all stages but is most pronounced during the active growth phases (tillering and heading) (Breidenbach et al., 2016). Proteobacteria, Chloroflexi, Bacteroidetes, and Acidobacteria are predominant phyla across all stages, but their relative abundances shift with plant development. For example, Proteobacteria are more abundant during the tillering and heading stages, while Acidobacteria increase towards the maturation stage (Liu et al., 2023). Functional groups such as iron reducers and fermenters are enriched in the rhizosphere, particularly during the early growth stages, indicating a dynamic interaction between plant roots and microbial communities. 4 Dynamic Changes in Rhizosphere Microbial Community Structure 4.1 Seasonal dynamic changes in microbial diversity and abundance The microbial community structure in the rice rhizosphere undergoes significant changes over the growing season. Studies have shown that the abundance of 16S rRNA genes in the rice rhizosphere is generally higher compared to unplanted bulk soil, indicating a stimulation of microbial growth in the rhizosphere (Breidenbach et al., 2016). Seasonal effects are particularly evident, with shifts in bacterial community structure observed at different plant developmental stages such as tillering, panicle initiation, flowering, and maturity (Schmidt and Eickhorst, 2013). For instance, the abundance of methanogenic archaea peaks at the flowering stage, highlighting the dynamic nature of microbial populations in response to plant growth stages. Additionally, the diversity of active microorganisms in the rhizosphere remains relatively stable across the growth stages, although the total microbial diversity may show little change (Li et al., 2019). Figure 1 The co-occurrence network of soil bacterial community in bulk (A), rhizosphere (B) and rhizoplane soils (C), the size of each node is proportional to its relative abundance. Zi-Pi plots showing the distribution of soil bacterial OTUs based on their topological roles in bulk (D), rhizosphere (E) and rhizoplane soil (F) (Adopted from Liu et al., 2023)
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