2 part Question -acid fast stain and observing capsules?

Question

#1. Which cells are acid-fast and what part of the cell allows this distinction?

#2. How do we observe capsules?

Answer 1

1) Mycobacteria and Corynebacteria are acid fast, because of a component (mycolic acid) of their cell walls.

2) capsules can be observed by staining the sample with India Ink. The ink is made up of small particles that cannot penetrate teh capsule, so when you add it to your slide, you'll see a clearing around the cell (zone of exclusion), that's where the capsule is.

Answer 2

John V. has already given you a very nice answer. to make it more closer, some bacteria like mycobacteria and some Corynebacteria contain mycolic acid, in their cell wall. Due to which these organisms are resistant to get decolorized by acids (like acid-alcohol, used in gram staining).. hence named,.. acid fast ..
http://en.wikipedia.org/wiki/Acid-fast

2. Capsules are relatively impermeable structures that cannot be stained with dyes. Mainly observerd using negative staining method,.. that is by using either India Ink or Nigrosine black, here capsules are observed against dark background.

Answer 3

if you're refering to "acid-fast staining", bacteria are identified by the staining. the disruption of the cell wall allows staining. the acid-fast staining should allow capsules to be viewed.