Question

a) What does 'mordant' refer to? In other words, what is the main function of Gram's iodine? -.IIIIIIIII b) Why do gram-negative bacteria lose their purple color when they are washed with 95% ethanol? Explain in terms of the prokaryotic structure that is affected by the alcohol and what the effect is. c) Why is the use of safranin necessary to Gram staining?

Answer 1

a) Mordant is a dye fixative / substance used to help dye in the process of binding Gram's iodine is a mordant used for Gram staining ... the helps too in the penetration of caystal violet deje and thus adheres gram. positive organisme. It combines with the stain & to increase the ability of staining of dye 60 Thollowing are the characterstier z gram negatia bacteria:- Gram negative bacteria e perplasmic space plasma membrane • peptidoglycan outer membrane Alchohol dissolves the lipide present in the outer cell membrane of gram negative bacteria. This lets out the crystal violent (dye) - - iodine complex to out of the thin peptidoglycas layer. This the gram positive retains crystal violent and the gram negative remain colourler. Hence Safranio, another counterstein is used to stain gram negatiue bacteria c) followed by the addition of alchohol/ decolonizing step, gram negative sto color, remains colourlen •so safranin /secondary stain gives wondrest to the gram negative cells to contrast with gram positive cells