Movie: Biomass-based model biofilm (mixed)
Movie of a biofilm growing from 10 cells per species at time zero for 30,000 min (3 weeks), with one frame per 1,000 min. All frames were rendered with POV-Ray, showing each biomass brick as a sphere. The biomass of the ammonia oxidisers ("Nitroso") is green; the biomass of the nitrite oxidisers ("Nitro") is red. These colours were chosen in order to make the overlapping of biomasses of the two species easily visible. The grey box at the bottom is the inert substratum. Note the wrapped around boundaries in the horizontal direction. Scale: total width of the system = 200 µm.
This Biomass-based model version (mixed) allows the coexistence of biomasses of the two species in the same grid element. Spreading of the two species is independent rather than coupled. This gives the random spreading process a greater chance to mix biomasses of the two species, effectively enhancing the spreading of the minority species. More cells of the minority species end up higher in the biofilm where they grow better.