Fixation and Staining of Bacteria.

Fixation and Staining of Bacteria. For each
experiment, 20 glass slides were cleaned wi th 95%
ethanol, and a circle with a diameter of 2 cm was
made on the surface of each slide using a wax pencil.
The 14 -hour culture of S. aureus was diluted 1/100 in
within the circle on each slide. Alterna
of the 14 - hour E. coli culture was spread within the
circle on each slide. The slides were then allowed to
air dry. One set of ten slides was heat- fixed by
passing the bottom of each slide through the flame of
a Bunsen burner until the slid e was warm to the
touch. The remaining ten slides were flooded with
. Excess methanol was decanted off the slides
into a waste disposal container, and t he slides were
allowed to air dry. All 20 slides were randomly
numbered 1 -20 so the individuals who stained and
viewed the slides did not know which slides were
heat -fixed versus methanol - fixed. The slides were
then stained using Hucker’s modified Gram -stain
technique and viewed independently
by three different individuals using a bright-field
light microscope . The experiment was completed
three and four times for E. coli and S. aureus ,
respec tively.