Fig. 2: Physical contact with Anabaena cells causes crystals to grow.

a Time-lapse images showing crystal growth as a result of Anabaena cell lysis within a crystal. Individual cells which were identified within the crystal are shown in blue outline. The yellow outline indicates the last frame the cell was observed before lysis. b The average chlorophyll intensity of the two cells tracked and the corresponding growth of crystal area. Dotted lines indicate the time when the individual cells lysed. c Time-lapse images showing nucleation and growth of a crystal at a sharp bend of a filament. The crystal growth appeared to be caused by cellular leakage due to mechanical stress at the bend. d, e Representative frames and plot showing that crystal growth does not occur due to proximity or contact with a vegetative cell. f Representative frames showing growth of a crystal after contact with a heterocyst (indicated by a caret). g Plot showing crystal area over time. Dotted line indicates the time of heterocyst contact at 37 h. All plots show the brightfield image in grayscale and chlorophyll fluorescence in red. All scale bars are 20 μm. h Model showing hypothesized mechanism behind vegetative cell leakage or lysis-based calcite precipitation. i Model showing hypothesized mechanism behind heterocyst contact-mediated calcite growth.