Heat fixing
slide is passed film-side up quickly through the flame of the alcohol lamp 2 to 3 times.
Alcohol fixing
consists of covering smear with 95% ethyl alcohol for 1 minute, then draining the alcohol
it denatures the protein, and it can cause the milk to curdle or coagulate making it clumpy which makes it hard to view
Why is heat fixing not suitable for preparations made up of milk
kill the microorganisms, coagulate the protoplasm of the cell and cause it to adhere to the slide
purpose of fixation
simple staining
only 1 dye used
Methylene blue
dye used in teeth scraping
Negative staining
dye does not adhere or stain the bacteria but rather the background
transparent
color of bacteria in negative staining
Nigrosin
dye used in negative staining
Differential staining
usage of 2 or more dye
Methylene blue
primary stain of differential staining
Basic fuchsin
secondary/ counterstain of the primary stain of Differential staining
pink or red due to the basic fuchsin
color of the cheek cells
dark blue or blue
color of the diplococcus salivarious
Ammonium oxalate-crystal violet
primary stain of gram staining
Mordant
used to intensify the chemical bond between the primary stain of the cell wall of the microorganism
Iodine
mordant used in gram staining
95% ethyl alcohol
decolorizer
safranin
secondary stain
usually gram negative
Plant pathogenic gram staining
Bacillus subtilis
gram positive
Escherichia coli
gram negative