3.1 Fluorescence-microscopical (FM) images of the
adsorbate layer
Figure 1 shows a characteristic example of FM-images of high
alloyed steel 1.4301 (UNS 304) after EPS-adsorption at 40 8C. One
can clearly see the difference between the images in the left and
the right column representing the non-immersed and the
immersed part of the sample, respectively. The single images
have been taken under the same conditions, e.g. with respect to
the duration of exposure. While the upper part of the sample was
not immersed and gives no rise for an FM-signal, the lower half
was covered by EPS-containing solution. The comparably high
intensity of the FM-images is thus due to the presence of a
carbohydrate adlayer but does not give information on other
chemical groups e.g. proteins. Images taken in the region of the
liquid-atmosphere boundary (not given here) sometimes show
higher intensity than those of the lower half. This is probably due
to the evaporation of the liquid and thus enrichment of EPS at the
phase boundary. No cells were visible under the FM indicating the
absence of bacterial cells in the suspension. In addition, that
proves that there was no contamination during the staining
procedure. Bacteria would also be stained by ConA as
carbohydrates are present on the cell surface.