Co-occurrence patterns between bacterial and fungal communities in response to a vegetation gradient in a freshwater wetland

Vegetation dynamics are known to influence belowground microbial community diversity and ecosystem processes in wetlands. However, the knowledge on microbe-microbe interactions in response to vegetation changes is scarce. In this study, we investigated how bacterial and fungal community composition, as well as bacterial-fungal community interactions, altered along a vegetation gradient in the Poyang Lake wetland. Surface soil and sediment samples were collected from three vegetation zones: dense, sparse, and naked. Vegetation zones differed in terms of dominant plant species, plant diversity, and vegetation coverage. Using Illumina MiSeq sequencing and network analysis of bacteria 16S rRNA and fungal ITS genes, we found that both bacterial and fungal community profiles varied according to vegetation conditions; in particular, the dense vegetation zone facilitated higher microbial abundance and a greater fungi to bacteria ratio. Co-occurrence analysis revealed that fungi-bacteria interactions were strong on vegetated zones, especially in the dense vegetation zone. However, a weak fungi-bacteria association was observed in the naked zone. Our results indicated that aboveground vegetation may act as a hotspot for organic matter accumulation, microbial growth, and microbe-microbe interactions, whereas fungi and bacteria prefer to distribute into niches based on their own nutritional preferences and functional specificity in bare ground.