Figure 6

Biofilm development during substrate limitation. Confocal scanning micrographs of C. thermocellum biofilms on Whatman #3 filter paper chads, taken approximately halfway through the ‘plateau’ (see figure 3) region. Low magnification images (below) show heavily populated fibers, some with very high cell-density biofilms, which were consistently observed throughout. Fibers with lesser colonization were observed typically deeper into the paper structure. High magnification imaging (above) of an extremely dense region shows the formation of numerous terminal sporangia, attached to the substratum at the non-sporulated end. Normal cells are still observed to line the surface of the same fibers. The regions indicated with white arrows show near-complete collapse of the cellulose fibers. Cells stained with SYTO 9 (green); cellulose fibers stained with WGA-TRITC (red).