Flagella Stain- Principle, Procedure and Result Interpretation


Flagella are long, thin, whip-like appendages that some bacteria use for locomotion. They are important for the identification and classification of bacteria, as they can vary in number, location, and arrangement on the cell surface. However, flagella are too thin and delicate to be seen with a regular light microscope and ordinary stains. Therefore, a special staining technique called flagella stain is used to visualize them.

The objective of flagella stain is to check whether a bacterium is motile or non-motile and to determine its flagellar pattern. This can help in the presumptive identification of motile bacterial species based on their flagellation. For example, some bacteria have a single flagellum at one end (monotrichous), some have multiple flagella at one or both ends (lophotrichous or amphitrichous), some have flagella all over the cell surface (peritrichous), and some have no flagella at all (atrichous). Different types of flagellation can be associated with different genera and species of bacteria. For instance, Escherichia coli is a peritrichous bacterium, Vibrio cholerae is a monotrichous bacterium, and Helicobacter pylori is a lophotrichous bacterium.

Flagella stain is a simple and useful technique when the number and arrangement of flagella are critical for the identification of motile bacteria. However, it requires an experienced laboratory scientist and is not considered an entry-level technique. It also depends on various factors such as the temperature, pH, age of culture, and quality of stain that can affect the stability and visibility of flagella. Therefore, flagella stains should be performed carefully and interpreted cautiously.