Figure 3.

The biofilm cells promote the formation of a alkaline microenvironment, required for calcium carbonate precipitation and morphogenesis. (a, b) Wild-type and ureA-C mutant biofilms were grown on solid biomineralization-promoting medium with a calcium source, at 30 °C, in a CO₂-enriched environment. (a) The intra-colony pH of wild-type (blue column) and ureA-C mutant strain (red column) on solid biomineralization-promoting medium, with acidic environment (pH 5.5). The results represent the averages and s.d. of three independent experiments. (b) Top view of a biofilm of wild-type B. subtilis (upper panel) and its ureA-C mutant (lower panel) derivative that grows in either an acidic (pH 5.5) or neutral (pH 7) environment, for 3 or 7 days. Images were taken by Stereo microscope with an objective ×0.5. Scale bar corresponds to 2 mm. The results are of a representative experiment out of three independent repeats. (c) Growth curves of wild-type (blue) and its ureA-C mutant derivatives (red) at 30 °C in liquid biomineralization-promoting medium. The results represent the averages and s.d. of six wells per strain, tested in three independent experiments.