Page 44 - MNUmicrobiology practical 2025
P. 44

General Microbiology & Immunology (PM 401)    second level    Semester 4       2024/2025


                  7. Flame the loop.

                  8.  Dry  the  suspension  by  warming  gently  over  a  Bunsen  burner  flame  (at  a

                     distance of 15 cm) and then ‘fix’ it by quickly passing it through the flame a few

                     times. This is called a heat-fixed smear; it should be visible to the naked eye as

                     a whitish area. Fixing is necessary to:


                      •  Ensure that cells adhere to the slide so they do not wash off when staining

                      •  Kill any bacteria that may be alive
                      •  Facilitate the stain penetration



                       Note

                     If you heat fix too little, the bacteria will wash off the slide. If you heat fix

                     too much, you will cook the bacteria and denature them.












































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