An Electron-microscopic Demonstration of an Acidic Polysaccharide Involved in the Adhesion of a Marine Bacterium to Solid Surfaces

SUMMARY: Staining a marine bacterium with Ruthenium Red and Alcian Blue demonstrated an extracellular, compact acidic polysaccharide layer, which was involved in bacterial adhesion to surfaces. The adhesive substance was present on suspended bacteria and appeared to assist adhesion when they were forced into contact with a suitable surface. Bacteria, which had attached to a surface naturally, produced a secondary fibrous acidic polysaccharide, which probably developed from the primary polysaccharide, and could eventually replace it. A high pH in the growth medium almost totally prevented the appearance of primary polysaccharide in preparations of naturally attached bacteria, which were surrounded by the reticular secondary polysaccharide, and adhesion was not impaired. In contrast to naturally attached bacteria, those forcibly attached were surrounded by primary polysaccharide. High temperature lowered the number of bacteria attached, relative to culture density, but did not affect the appearance of the adhesive substance.