Figure 4. Scanning electron micrographs of 10-day-old biofilms.

Individual bacilli, identified as Lactobacillus spp. (day 5) (arrows) are covered by a light glycocalyx (4A (i)) and a control ATCC strain Bacteroides spp. (day 5) by a more mature biofilm (4A (ii)) both captured at × 10000 magnification. Figures 4B (i (day 5) and ii (day 10)) represent osmium fixed biofilms containing coccoid bacteria identified as Streptococcus spp. (by culture) (arrows) at × 15000 and × 30000 magnification. Glycocalyx is not well preserved using traditional aldehyde fixatives followed by OsO₄ post-fixation. Figure 4C (i) (day 10) was fixed using OsO₄, which stabilises lipids and figure 4C (ii) (day 10) was fixed using an aldehyde fixative followed by OsO₄ plus ruthenium red to enhance the preservation of the anionic polysaccharides in the glycocalyx.