gram staining

Question 1

what are the results for gram positive bacteria?

Answer 1

stained purple, as it has a thick peptidoglycon layer (cell wall) which dehydrates at the addition of alcohol, traps crystal violet stain inside

Question 2

what are the results for gram negative bacteria?

Answer 2

pink stained- has more complex cell wall with a fatty layer, so when alcohol is applied the stain washes off. Saffranin is added and can be easily seen

Question 3

what is the method for gram staining?

Answer 3

1) Bacteria culture is smeared onto a slide
2) Heat is applied to fix the bacteria onto the slide
3) Crystal violet stain is applied, wash with water
4) Iodine is applied to trap cv onto cell
5) Alcohol is applied as a wash (decolourisation of stain)
6) Counterstain of saffranin to stain untouched bacteria
7) Blot with paper towel and examine under a microscope

Question 4

what are the pros of a light microscope?

Answer 4

cheap, view live specimens, easy to use and can see a colour image with stains

Question 5

what are the pros of an electron microscope?

Answer 5

high magnification, high resolution

Question 6

what are the negatives of a light microscope?

Answer 6

low magnification, low resolution

Question 7

what are the negatives of an electron microscope?

Answer 7

specimen has to be dead, expensive