Which of the following is not characteristic of the glycocalyx found in bacteria?
a. a viscous coating surrounding the cell made of polysaccharide, polypeptide, or both
b. creates a slimy, slippery coating that prevents bacteria from attaching to surfaces
c. if firmly attached, contributes to bacterial virulence
d. a structure that can be visualized using an acidic negative stain and a basic counterstain