Photogranules are found in nature as cryoconite granules on glaciers or microbialites in marine waters. This growth form of phototrophic communities has advantages also for biotechnological applications, as biomass is easily settleable and produces oxygen in-situ, thus eliminating costly aeration. To use photogranules in biotechnology, it is beneficial to better understand the initial requirements for their development. We use a laboratory system in which we can monitor photogranulation using activated sludge as starting matrix. In this presentation, we investigate how the spatialization of the developing phototrophic ecosystem can be altered by cyanobacterial augmentation. We hypothesized that gliding filamentous cyanobacteria present in the outer layer of already formed photogranules possess the trait to form the spherical structure of a photogranule in climax state. We augmented activated sludge from five sources with increasing amounts of phototrophic communities or cyanobacterial strains. During the development of a phototrophic ecosystem, we observed, the formation of a range of morphotypes: microbial mats, hemispheroids and spherical photogranules. This distribution of morphotypes could be altered by augmenting the sludge with sufficiently high concentrations of cyanobacteria. The resulting distribution was then dominated by the type-morphotype of the added strain when grown in isolation in synthetic medium. The coupling of the initially present type and abundance of cyanobacteria to the deterministic trajectory of morphotype development aids in ecological engineering. The cyanobacterial ecosystem engineers were low in abundance or absent in the final microbial communities, in which always mat- forming cyanobacteria dominated. If this also holds true for naturally occurring photogranules, we cannot obtain insight into the ecosystem engineer by studying the final microbial communities, as often done in studies of these ecosystems. Our model ecosystem allows us to shed light on the succession of cyanobacteria with different traits and eventually on the spatial outcome of photogranulation.