We found that both gram-positive (S.
aureus) and gram-negative (E. coli) bacteria that
were fixed to slides using methanol as the fixative
agent adhered more effectively than did cells that
were heat-fixed to slides. Slides of S. aureus fixed
with methanol had two to four times as many cells
present than did slides fixed with heat. In the case of
E. coli, the difference was even more dramatic with
five to ten times as many cells present on methanol-fixed slides compared to slides that were heat-fixed.
Methanol fixation prior to Gram staining would
clearly allow students to locate and view bacterial
cells more easily than heat fixation