The diversity pattern of soil bacteria in the rhizosphere of different plants in mountain ecosystems

Research on the composition and diversity of rhizosphere microbial communities of different plant species can help to identify important microbial functional groups or functional potentials, which is of great significance for vegetation restoration and ecological reconstruction. To provide scientific basis for the management of mountain ecosystem, the diversity pattern of rhizosphere bacterial community was investigated using 16 S rRNA high-throughput sequencing method among different host plants (Cirsium japonicum, Artemisia annua, Descurainia sophia, Lepidium apetalum, Phlomis umbrosa, and Carum carvi) in Tomur Peak National Nature Reserve, China. The results showed that the richness and diversity of rhizosphere bacteria were highest in Descurainia sophia, and lowest in Lepidium apetalum. Pseudomonadota, Acidobacteriota, and Actinomycetota were the common dominant phyla, and Sphingomonas was the predominant genus. Furthermore, there were some specific genera in different plants. The relative abundance of non-dominant genera varied among the plant species. Canonical correspondence analysis indicated that available potassium (AK), total phosphorus (TP), total potassium (TK), and soil organic matter (SOM) were the main drivers of bacterial community structure. Based on PICRUSt functional prediction, the bacterial communities in all samples encompass six primary metabolic pathways and 47 secondary metabolic pathways. The major secondary metabolic pathways (with a relative abundance of functional gene sequences > 3%) include 15 categories. Co-occurrence network analysis revealed differences in bacterial composition and interactions among different modules, with rhizosphere microorganisms of different plants exhibiting distinct functional advantages. This study elucidates the distribution patterns of rhizosphere microbial community diversity in mountain ecosystems, which provides theoretical guidance for the ecological protection of mountain soil based on the microbiome.

Source and acquisition of rhizosphere microbes in Antarctic vascular plants

Rhizosphere microbial communities exert critical roles in plant health, nutrient cycling, and soil fertility. Despite the essential functions conferred by microbes, the source and acquisition of the rhizosphere are not entirely clear. Therefore, we investigated microbial community diversity and potential source using the only two native Antarctic plants, Deschampsia antarctica (Da) and Colobanthus quitensis (Cq), as models. We interrogated rhizosphere and bulk soil microbiomes at six locations in the Byers Peninsula, Livingston Island, Antarctica, both individual plant species and their association (Da.Cq). Our results show that host plant species influenced the richness and diversity of bacterial communities in the rhizosphere. Here, the Da rhizosphere showed the lowest richness and diversity of bacteria compared to Cq and Da.Cq rhizospheres. In contrast, for rhizosphere fungal communities, plant species only influenced diversity, whereas the rhizosphere of Da exhibited higher fungal diversity than the Cq rhizosphere. Also, we found that environmental geographic pressures (i.e., sampling site, latitude, and altitude) and, to a lesser extent, biotic factors (i.e., plant species) determined the species turnover between microbial communities. Moreover, our analysis shows that the sources of the bacterial communities in the rhizosphere were local soils that contributed to homogenizing the community composition of the different plant species growing in the same sampling site. In contrast, the sources of rhizosphere fungi were local (for Da and Da.Cq) and distant soils (for Cq). Here, the host plant species have a specific effect in acquiring fungal communities to the rhizosphere. However, the contribution of unknown sources to the fungal rhizosphere (especially in Da and Da.Cq) indicates the existence of relevant stochastic processes in acquiring these microbes. Our study shows that rhizosphere microbial communities differ in their composition and diversity. These differences are explained mainly by the microbial composition of the soils that harbor them, acting together with plant species-specific effects. Both plant species acquire bacteria from local soils to form part of their rhizosphere. Seemingly, the acquisition process is more complex for fungi. We identified a significant contribution from unknown fungal sources due to stochastic processes and known sources from soils across the Byers Peninsula.