What Is Flagella? Types And Staining Procedure

If you’re interested in biological cells, then you might have seen the term flagella coming up often, but not known what it referred to. What is flagella? 

What Is Flagella? Types And Staining Procedure

Our helpful guide below will tell you all about it, as well as the different types that exist. On top of that, we have a guide on how to stain them in order to help identify the species.

What Is Flagella?

Flagella is a slender and long filamentous cytoplasmic structure that protrudes through a cell wall. Their own cell envelope is filled with protein called flagellin, and the flagella as a whole is unbranched.

Flagella are the cause of bacterial motility, which is an essential part in the survival of a bacteria, and affects the ability for the bacteria to provoke disease. 

Flagella Measurements

Flagella (singular: flagellum) can have a length of anywhere between 5 and 16 μm, while its diameter is capable of measuring anywhere between 12 and 30 nm. “Nm” stands for nanometer, which is one billionth of a meter. 

What Do Flagella Do?

Flagella have many functions and assist with many different things. For one thing, they help with movement and chemotaxis for the bacteria, allowing it to be mobile.

Flagella propel cells by spinning their axis around in a type of motion akin to a corkscrew. On top of that, they also assist bacteria with sensation. 

For a cell that is anchored in tissue, flagella help to move liquid over the surface of the cell. An example of an anchored cell would be the epithelial cells that line our air passages, and the way that flagella helps is to help push particle-laden mucus towards our throat. 

On top of all these helpful functions, flagella also assist with adhesion, as well as signal transduction.

Signal transduction is the term given to the transmission of molecular cells from the exterior of a cell to the interior. They do this through three stages: reception, transduction, and response. 

Types Of Flagella

Below are 4 types of ways that you and scientists will find flagella distributed on a bacteria. Alongside these types, we’ve included examples of bacteria where you would find them.

1. Monotrichous

These have a single flagellum at one pole. Visually, this will look like there is just one single strand of long hair (if you will) sticking out of the bacteria cell body.

An example of a bacteria with monotrichous distribution of flagella would be vibrio cholerae. These bacteria are shaped like commas, and are facultative anaerobe – as well as being Gram-negative. 

The term “Gram-negative”, if you don’t know, is given to bacteria that cause things like infections of the bloodstream and pneumonia. They are resistant to many drugs and antibiotics.

When a Gram staining method is used on them for bacterial differentiation, they do not keep the crystal violet stain – hence they are “Gram-negative.”

2. Peritrichous

From one flagella to loads. This is the name for when there are lots of flagella all over the body of the bacteria. If you picture it visually, it will look like the bacteria cell body is hairy in a sense, with lots of different long strands coming off it.

An example of a bacteria that has peritrichous distribution would be salmonella typhi. This is another Gram-negative bacterium. 

3. Amphitrichous

This is the term for when there is a single flagellum on both sides of the bacteria cell body. Visually, it’s a rectangular cell body with a single long strand sticking out from either end of it, going outward in different directions.

An example of a bacteria with this would be alkaligens faecalis.

4. Lophotrichous

When a bacteria has a layout of flagella coming off it in the quantity of tufts, be they at one or both sides, this is the name given to the distribution.

Visually, it looks like a cell body with a few long strands coming off one end, or both ends in some circumstances. An example of a bacteria with this is spirillum.

5. Flagella Parts

Each individual flagellum has three parts to it. The basal body is attached to the cytoplasmic membrane through some ring shaped structures.

Then the hook is a part embedded into the cell envelope, while the filament is a piece that is external to the cell itself. 

How To Flagella Stain

  1. To start, grow the organisms that you want to stain on blood agar plates. They should be grown by room temperature for 16-24 hours. 
  2. Once that’s done, take a microscope slide and add a droplet of water, then dip an inoculating loop into some sterile water. The loop should be sterile, too. 
  3. Then take the loopful of water and briefly touch it to the colony margin. Motile cells will enter the water, then touch that loop to the slide’s water.
  4. Cover the water with a cover slip, with tiny air spaces on the edges. 
  5. Immediately examine it under 40x magnification. If you see motile cells, leave the slide for 10 minutes. 
  6. Apply 2 RYU flagella stain drops on the slip’s edges. Wait 10 minutes (keeping room temperature), then examine the cells at 100x magnification for flagella.

Final Thoughts

Use our guide to identify the arrangements of flagella on bacteria cells, identifying the bacteria. 

Jennifer Dawkins

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