Fig. 2

The comparison of algae cell in coculture and axenic culture. a The growth curve of algae cell in coculture (open triangles), axenic Synechococcus sp. PCC 7002 in the presence (filled squares) or absence (open squares) of vitamin B₁₂. The basal medium of the cultures is BG11 medium (see “Materials and methods” section). Obviously, the axenic cyanobacterium is unable to grow in the absence of vitamin B₁₂; b the scanning electron microscopy (SEM) image of cells in coculture (bottom right panel) and axenic culture (bottom left panel)