2. *One of the most important techniques in bacteriology is the Gram stain, first described by Hans-Christian Gram in 1884. it allows the differentiation of bacteria into two groups: have a thick cell wall made of peptidoglycan Gram-positive have a thinner layer Gram-negative

5. 2- Place one needle of solid bacterial growth, and with your inoculating loop, mix it with the water completely and spread the mixture.

6. 3- wait for it to dry.then Heat-Fix the smear by quickly passing the slide through a flame two or three times. The smear is now ready for the staining.

14. results in a purple/blue color Gram-positive results in a pink/red color Gram-negative

17. can retain a complex made between crystal- violet and iodine when decolourised with acetone Gram- positive are decolourised on treatment with acetone Gram- negative