Land use and Season Drive Compositional Shifts in Cyanobacteria-dominated Soil Bacterial Communities

Cyanobacteria-dominated bacterial communities in soils were investigated using a selective cultivation approach to evaluate the effects of land use and season. Soils were sampled from cropland and non-agricultural terrestrial habitats in spring and autumn, and microbial growth was enriched on modified Bristol medium lacking inorganic nitrogen before being analyzed by 16S rRNA gene sequencing. Alpha diversity did not differ significantly between land-use types or sampling seasons, indicating that functional selection imposed by cultivation constrained within-sample diversity. In contrast, community composition showed consistent differentiation across both factors. Multivariate analyses demonstrated that land-use- and seasonrelated patterns were primarily driven by shifts in a limited number of cyanobacteria-associated heterotrophic bacterial genera. In contrast, filamentous cyanobacteria showed comparatively stable representation across environments and seasons. These results indicate that, within functionally selected soil microbial systems, environmental signals are more effectively captured by changes in associated bacterial partners than by variation in cyanobacterial diversity or dominance.