Particle-size dependent of bacterial diversity associated with suspended particulate matter continuum in Lake Taihu.

Suspended particulate matter (SPM) of varying particle sizes is widespread in aquatic ecosystems, providing crucial habitats for bacteria and serving as hotspots for mineralization and nutrient cycling. However, prior studies have typically treated bacteria associated with these particulates as a homogeneous group, overlooking size-related differences in diversity and composition. In this study, we separated the SPM continuum into five size-fractions (0.2, 2, 20, 200, and 500 µm) and investigated bacterial diversity, community assembly, and environmental drivers across four representative regions of Lake Taihu, China, over 1-year period. Using 16S rRNA gene sequencing, we observed particle-size-dependent variations in bacterial diversity. Alpha diversity decreased significantly with increasing particle size, while beta diversity showed a similar trend. Environmental factors influencing species richness varied by particle size, while bacteria associated with smaller particles (0.2, 2, and 20 µm) were more sensitive to environmental factors compared to those associated with larger ones (200 and 500 µm). The role of deterministic processes in community assembly increased with particle size, indicating stronger selection on larger particles. This study enhances our understanding of bacterial diversity in aquatic ecosystems and highlights the importance of particle size in bacterial community dynamics.