Construction of photogranules by varying the initial cyanobacterial addition

We augmented five activated sludges with increasing amounts of phototrophic communities or cyanobacterial strains. The initial type and abundance of cyanobacteria determined the ecosystem's morphotype. Augmentation of sludge in sufficient concentrations steered morphotype development into the direction of the morphotype typically formed by the strain grown in synthetic medium. Final communities were always dominated by mat-forming cyanobacteria, whereas photogranule-formers were low abundant or absent. The presence of photogranule-formers was only required for the initiation of photogranulation. Communities were described based on 16S rRNA gene amplicons of the V4-V5 region and 23S rRNA gene amplicons.