Fig. 6

Scanning electron microscopy of mineral precipitates formed under biofilm-promoting conditions. Crystals precipitated on colonies of W∆-H-BpU (left panels) and W∆-∆d-H-BpU (right panels) were grown on LBGMC agar containing urea and xylose at 30 °C for 1–2 weeks. Crystals removed from the colony surface were imaged on an SEM with gold splutter coating. A Areas of view showing boundaries between porous sections of the precipitate in the left half of the images, with the smooth layer visible towards the right side of the images. Closed arrows indicate smooth areas of precipitate, presumably formed within the extracellular biofilm matrix; open arrows indicate voids in the porous areas of precipitate B Views of porous sections of the precipitate. Open arrows indicate voids or bacterial ‘footprints’ in the precipitate, presumably caused by precipitation closely around the bacterial cells. Sizes of scale bars are given in each image