Fig 4. Stereo microscope images showing discoloration of damaged cells after exposure of UVB at 302 nm.

Partially infiltrated cyanobacterial biofilms into muscovite (A), phlogopite (B), and biotite (C) sheets were exposed to UVB for 6 hours. The edges of mineral sheets are highlighted with black curves. The biofilms protected underneath mica sheets (the lower right portion of the images) remained green in color, while those regions without any mica protection (the upper left regions, indicated by red arrows) showed discoloration. Images were taken looking down the C-axis. Each scale bar represents 50 microns.