Fig 2 -

Real-time evolution of (a) pH and (b) OD_750nm for MICP experiments with the presence of calcite seeds. Note that the first shown data point of the measurement is taken 4 min after the start of the reaction. The OD_750nm was measured before start of the reaction to get the contribution of the initial seeds in the crystallization solution, and this starting value was subtracted from the OD_750nm. Therefore, the shown signal is correlated to the amount of precipitated CaCO₃. The OD in the legend shows the OD_600nm of the bacteria dilution before adding to the crystallization solution. (c) Optical microscope time-series of the precipitation process for bacteria dilution with OD_600nm = 0.88 with calcite seeds present for different time-points of the reaction: (i) 0 min, (ii) 20 min, (iii) 28 min, (iv) 50 min, (v) 80 min, (vi) 110 min, (vii) 170 min, (viii) 230 min, and (ix) 21 h. The magnified area on the right shows calcite seeds that will increase in size during the experiment. The magnified area on the left shows an area with a small distance to calcite seeds that will increase in size during the experiment. (d) Comparison of real time pH evolution of MICP experiments with and without calcite seeds. (e) Micrographs of precipitated crystals after 21 h reaction time for (1) D1-C1_s, (2) D2-C1_s, (3) D3-C1_s, and (4) D4-C1_s. The red arrows indicate calcite seeds that grew during the experiment and the blue arrows indicate additional nucleated calcite crystals. The scale-bar is 50 μm in (c) and 150 μm in (e).