The first chemical used in the Gram stain, crystal violet, binds to negatively charged parts of the bacterial cell. The second chemical, Gram’s iodine, acts as a mordant – a chemical that enhances the reactivity of a stain for tissue. Thus, Gram’s iodine is used to increase the tightness of bond between crystal violet and the bacterial cells. Though it has a brownish color, Gram’s iodine does not alter the color of the bacterial smear due to its use. <\/p>\n\n\n\n
Gram’s decolorizer is the third chemical used during the Gram stain procedure. At this point in completion of a Gram stain, Gram positive and Gram negative cells all are the same purple color. Gram’s decolorizer will remove the crystal violet\/iodine complex from Gram negative bacteria but Gram positive bacteria remain stained.<\/p>\n\n\n\n
Gram’s decolorizer can be either ethanol or acetone, both of which are lipid solvents that also dehydrate cells. Gram positive and Gram negative cells differ in the structure of their cell walls. Gram positive walls have thick peptidoglycan – 20 sheets or so of the cell wall fabric. Gram negative cell walls have much less peptidoglycan (5 sheets or so) but have an outer wall membrane made of lipid material. Peptidoglycan shrinks during decolorizer use, keeping the crystal violet\/iodine complexes in Gram positive cells. But decolorizer manages to remove the crystal violet\/iodine complexes from Gram negative bacteria because of too little peptidoglycan to hold it in, and the dissolving of the outer membrane. The result is the Gram positive bacterium remains purple following use of Gram’s decolorizer, while the Gram negative bacterium has lost its stain and appears clear.<\/p>","protected":false},"excerpt":{"rendered":"
The first chemical used in the Gram stain, crystal violet, binds to negatively charged parts of the bacterial cell. The second chemical, Gram’s iodine, acts as a mordant – a chemical that enhances the reactivity of a stain for tissue. Thus, Gram’s iodine is used to increase the tightness of bond between crystal violet and […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","template":"","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"doc_category":[39],"doc_tag":[],"knowledge_base":[44],"class_list":["post-12014","docs","type-docs","status-publish","hentry","doc_category-reagents-chemicals-stains","knowledge_base-reference"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t