gram twort

Question 1

purpose/target of gram twort stain

Answer 1

Differentiate gram positive and gram negative bacteria

Question 2

what are the 2 counterstains for gram twort?

Answer 2

fast green FCF and neutral red/twort stain

Question 3

control tissue for gram twort

Answer 3

appendix

Question 4

what colour will gram positive bacteria stain in gram twort

Answer 4

purple (crystal violet)

Question 5

what colour will gram negative bacteria stain in gram twort

Answer 5

red (Twort stain)

Question 6

what colour will nuclei and cytoplasm stain in gram twort?

Answer 6

Nuclei = red (twort stain)
cytoplasm = green (fast green FCF)

Question 7

In the Brown and Brenn modification of gram twort stain, what are the 2 different counterstains instead of fast green fcf and neutral red?

Answer 7

basic fuchsin and picric acid

Question 8

principle/mechanism of staining for gram twort?

Answer 8

Regressive staining.

Gram positive contain multiple interlinked peptidoglycan layers, &
Gram negative contain thin layer of peptidoglycan.

Crystal violet (+) binds to phosphate (-) in nucleic acid in both, followed by Lugol’s iodine mordant which stains both types of bacteria purple

Decolorizer (acetone-alcohol) disrupts lipoprotein layer and the remaining peptidoglycan layer cannot retain, so gram negative is decolorized and turns red.
Counterstain taken up by gram negative only.
Gram +ve bacteria stays purple

Question 9

purpose of lugol’s iodine in gram twort

Answer 9

mordant

Question 10

purpose of acetone-alcohol in gram twort

Answer 10

decolourize

Question 11

what substance decolorizes bacteria in gram twort

Answer 11

acetone-alcohol

Question 12

what acts as the mordant in gram twort

Answer 12

lugol’s iodine

Question 13

primary stain in gram twort?

Answer 13

crystal violet