ACID FAST Stain PDF

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Summary

Learning another method of staining bacteria (such as mycobacteria) and the method to do so in a proper fashion. We are also going to learn about advantages and disadvantages of this staining method...

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ACID FAST STAIN Purpose: WHAT IS THE AIM OF TODAY’S LAB?

Learning another method of staining bacteria (such as mycobacteria) and the method to do so in a proper fashion. We are also going to learn about advantages and disadvantages of this staining method Materials:

• Acid fast reagents: Kinyoun carbolfuchsin, acid alcohol and methylene blue • Cultures: 

Mycobacterium smegmatis/phlei (slant)



Staphylococcus epidermidis (broth)

Methods: (Write down what you did, step by step) Refer to pages 35 in the BIOL302 Lab manual. The instructor conducted the lab and result was given

Results: (Any graphs? Screen shot/cropped data? Etc

Figure legend: (Briefly and concisely explain what data I am looking at)

These pictures shows the result of acid-fast stained bacteria samples. On the top right we have the Non Acid-fast organism and on the top left, we have acid fast organism Discussion: (Interpret what you see, why it is important, and why it look that way. Any improvements? Future direction?

These 2 pictures show samples of acid-fast stain. On the top left red stained mycolic acid layers can recognize the Acid-fast organism. The bacteria on top right shows a blue stain, meaning that it does not have mycolic acid layers and so it shown the blue color after the final wash. This indicates that top left sample have mycolic acid layer and is an acid fast organism (mycobacteria) but the sample on the right lacks the mycolic acid layer and so became blue instead. Using thus method we can distinguish bacteria and see if they are acid fast or not.

Questions: (Answer all questions found from your lab manual section)

1. When subjected to the Gram stain, mycobacteria either stain weakly red or do not stain at all. Explain why, describing the differences between the cell envelopes of acid-fast, gram positive, and gramnegative bacteria.

The acid-fast organisms have mycolic acids layer. It is made of a waxy lipid layer in cell envelopes and it makes the cell impermeable to most of stains. Gram-positive cell envelope is made of cytoplasmic membrane, cell wall and capsule. The gram-negative cell envelope is made of cytoplasmic membrane, cell wall, periplasmic space, outer membrane and capsule. Mycobacteria however, has an extra layer of mycolic acid layer.

2. Synthesizing cell walls with mycolic acids requires a great deal of energy. Do you expect acid-fast bacteria to grow fast or slow compared to other bacteria? Explain. I would predict for them to be much slower. The production of mycolic acid cell walls take a lot of energy for a bacteria, and since it takes the energy from its production, there would not be any more left to use on rapid growth and replication.

3. What are the chemical differences between the Gram stain and the acid-fast stain?

Dyes used in acid-fast stain are different from ones used in gram stain We use acid alcohol instead of alcohol, which is used in gram stain. Instead of alcohol, acid-fast stain use acid alcohol. We also do not use iodine, and instead use heat fix for dye binding....