Flagella Staining:

Flagella are fine, threadlike organelles of locomotion and are too small to be seen with light microscope and can be directly seen using Electron Microscope

•  To observe them with light microscope, the thickness of flagella is increased by coating them with mordants like tannic acid and potassium alum and they are stained with pararosanilins (Leifson method) or basic fuchsin (Gray method)

•  Microbiologists use the number and arrangement of flagella as diagnostic aid (Fig. 17)

 

Fig. 17 . Flagella staining

Negative staining:

•  Reveals the presence of the diffuse capsules surrounding many bacteria.

•  Bacteria are mixed with India ink or Nigrosin dye and spread out in a thin film on a slide.

•  After air drying, bacteria appear as lighter bodies in the midst of a blue-black background because ink and dye particles cannot penetrate either the bacterial cell or its capsule (Fig. 18).

•  It is valuable in the observation of overall cell shapes, sizes and capsules

 

Fig. 18. Capsule staining

REFERENCES:

Text Books:

1. Jeffery C. Pommerville. Alcamo's Fundamentals of Microbiology (Tenth Edition). Jones and Bartlett Student edition.

2. Gerard J. Tortora, Berdell R. Funke, Christine L. Case. Pearson - Microbiology: An Introduction. Benjamin Cummings.

Reference Books:

1. Lansing M. Prescott, John P. Harley and Donald A. Klein. Microbiology. Mc Graw Hill companies.