Rhizosphere Soil Microbial Community Under Ice in a High-Latitude Wetland: Different Community Assembly Processes Shape Patterns of Rare and Abundant Microbes

Variation and assembly mechanisms of Rhinolophus ferrumequinum skin and cave environmental fungal communities during hibernation periods

Animal skin acts as the barrier against invasion by pathogens and microbial colonizers. Environmental microbiota plays a significant role in shaping these microbial communities, which, in turn, have profound implications for host health. Previous research has focused on characterizing microorganisms on bats' skin and in their roosting environments, particularly bacterial communities. The emergence of white-nose syndrome, caused by the fungal-pathogen Pseudogymnoascus destructans, highlights the importance of understanding fungal dynamics in cave ecosystems and on bats' skin. In this study, we employed ITS amplicon sequencing to investigate the fungal community associated with the skin of Rhinolophus ferrumequinum and surfaces within hibernacula. In addition, we utilized neutral community and null models to assess the relative importance of stochastic and deterministic processes in fungal community assembly. The infection status of P. destructans did not significantly impact fungal community composition either on bat skin or cave environments. However, fungal diversity was significantly higher in cave environments compared to bat skin. Notably, potentially inhibitory genera of fungal pathogens were present in both bats and cave environments during hibernation. Furthermore, the composition and structure of fungal communities on both bat skin and cave environments varied across hibernation periods. Our findings suggest neutral processes primarily drive the assembly of fungal communities associated with hibernating R. ferrumequinum and cave environments, with dispersal limitation exerting a significant influence. This study provides insights into the fungal communities associated with hibernating R. ferrumequinum and cave environments.IMPORTANCEAnimal habitats provide sources and reservoirs for host microorganisms, making it critical to understand changes in microbial communities between habitats and hosts. While most studies have focused on bacterial microorganisms, research on fungal communities is lacking. This study investigated how community dynamics and assembly processes differ between the skin of hibernating Rhinolophus ferrumequinum and the cave environments under pathogen stress. We found significant differences in the composition and structure of the fungal communities between bat skin and roosting cave environments. Fungal genera with potential inhibitory effects on pathogens were found in all bat skin and cave environments. In addition, dispersal limitations during stochastic processes were a key factor in the formation of environmental fungal communities on bat skin and in caves. These findings offer new insights for exploring pathogen-host-environment-microbe interactions.

Plant diversity increases diversity and network complexity rather than alters community assembly processes of leaf-associated fungi in a subtropical forest

Plant diversity significantly impacts ecosystem processes and functions, yet its influence on the community assembly of leaf fungi remains poorly understood. In this study, we investigated leaf epiphytic and endophytic fungal communities in a Chinese subtropical tree species richness experiment, ranging from 1 to 16 species, using amplicon sequencing to target the internal transcribed spacer 1 region of the rDNA. We found that the community assembly of epiphytic and endophytic fungi was predominantly governed by stochastic processes, with a higher contribution of dispersal limitation on epiphytic than on endophytic fungal communities but a higher contribution of selection on endophytic than on epiphytic fungal communities. The plant-epiphytic fungus interaction network was more complex (e.g., more highly connected and strongly nested but less specialized and modularized) than the plant-endophytic fungus interaction network. Additionally, tree species richness was positively correlated with the network complexity and diversity of epiphytic (α-, β- and γ-diversity) and endophytic (β- and γ-diversity) fungi, but was not associated with the contribution of the stochastic and deterministic processes on the community assembly of epiphytic and endophytic fungi. This study highlights that tree species diversity enhances the diversity and network complexity, rather than alters the ecological processes in community assembly of leaf-associated fungi.

The process of nitrogen-adaptation root endophytic bacterial rather than phosphorus-adaptation fungal subcommunities construction unveiled the tomato yield improvement under long-term fertilization

Interactions between endophytes (endophytic bacteria and fungi) and plants are crucial in maintaining crop fitness in agricultural systems, particularly in relation to abundant and rare subcommunities involved in community construction. However, the influence of long-term fertilization on heterogeneous rhizosphere nitrogen and phosphorus environments and how these conditions affect the key subcommunities of root endophytes and their community assembly mechanisms remain unclear. We studied the 26th year of a field experiment conducted in a greenhouse with varying levels of nitrogen and phosphorus (CKP0, CKP1, CNP0, CNP1, ONP0, and ONP1) to assess the composition of tomato root endophytes and their impact on yield. We employed 16S rRNA and fungal ITS region amplicon sequencing to investigate the assembly mechanisms of abundant and rare endophytic subcommunities, network correlations, core subcommunity structures, and key species that enhance crop yield. The results indicated that organic manure and phosphorus fertilizers significantly increased the rhizosphere soil nitrogen content, phosphorus content, and phosphorus availability (labile P, moderately labile P, and non-labile P). These fertilizers also significantly affected the composition (based on Bray-Curtis distance) and community assembly processes (βNTI) of endophytic microbial subcommunities. The assembly of both bacterial and fungal subcommunities was primarily governed by dispersal limitation, with community structures being significantly regulated by the content of rhizosphere soil available nitrogen (AN) and moderately labile P (MLP). Rare bacterial and fungal subcommunities complemented the ecological niches of abundant subcommunities in the co-occurrence network, supporting community functions and enhancing network stability. Nitrogen-adapting abundant and rare bacterial subcommunities provided a stronger predictive correlation for tomato yield than phosphorus-adapting fungal subcommunities. Additionally, three core genera of rare endophytic bacteria such as Arthrobacter, Microbacterium, and Sphingobium were identified as potentially involved in improving crop yield improvement. These findings revealed the distinct assembly mechanisms of endophytic microbial subcommunities affected by fertilization, enhancing our understanding of better management practices and controlling endophytes to improve crop yield in intensive agricultural ecosystems.