h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

That was a very good guide to Gram staining techniques, especially the substitutes, but how about putting in some of the biological theory (i.e. how the crystal violet works,etc)? I'd be happy to help, if you like!

Hi, thanks!
Weeeelll, in Gram positive bacteria, the crystal violet stain forms purple complexes with the iodine, and these get lodged in the giant, net-like molecules that are present in the cell walls of gram-positive bacteria. These molecules are long chains of amino acids and sugars, called peptidoglycans, and form a kind of net that the stain gets stuck in, and can't get out even after irrigation with alcohol.
The reason Gram-negative bacteria don't stain purple is because their cell walls don't have peptidoglycans, and have a relatively impermeable membrane. The red safranin dye simply makes them show up under a microscope.
Whew! I didn't know whether to include that in the article, it seemed a bit long-winded and complicated...

thanks for your offer to help, have you studied biology?