Introduction to Prokaryotic Flagella: Videos & Practice Problems

Prokaryotic flagella, or flagellum in singular, are filamentous proteins that enable bacterial motility. They can be categorized based on their distribution: atrichous (no flagella), polar (flagella at one or both poles), and peritrichous (flagella covering the entire surface). Specific types include monotrichous (one flagellum), lophotrichous (multiple at one pole), and amphitrichous (one at each end). Understanding these distributions aids in identifying bacteria and their movement capabilities in various environments.

Introduction to Prokaryotic Flagella

In this video, we're going to begin our introduction to prokaryotic flagella, which is a little bit different than eukaryotic flagella. And so flagella is actually the plural form of the word. The singular form is actually flagellum. And so these flagella are really just long filamentous surface proteins that drive motility of cells, or in other words, they help to propel the cell through its environment to allow the cell to move throughout its environment. Now the term tuft is actually referring to a group of many flagella on the surface of a cell. And so if we take a look at this image down below, notice that we're showing you a bacterium here, a single bacterial cell. And notice that it has these long filamentous surface proteins that are extending off of it, and these are the flagella, or the individual one is the flagellum. Now a group of a bunch of flagella, as we see here, is collectively referred to as a tuft. And these flagella, what they can do is they can move in a very specific way to act as a propeller, to propel the bacterial cell through its environment so that it is capable of moving in a specific direction. And so you can see here that we've got a car that's in motion to show that these flagella are important for motility and for the movement of the cell. And so these flagella can actually be distributed in many different ways across the bacterial surface. And so in our next video we're going to focus on the distribution of these flagella, and the different types of distribution. And so this here concludes our brief introduction to prokaryotic flagella, and we'll be able to continue to learn more and more about them as we move forward. So I'll see you all in our next video.

Types of Flagellar Distribution on Bacteria

In this video, we're going to talk about the types of flagellar distribution on a bacterial surface. Bacterial cells are categorized into multiple groups based on the distribution of the flagella across the bacterial cell surface. The flagellar distributions can be used to identify specific types of bacteria. Notice below, we have an image with various flagellar distributions.

On the top left, the first distribution is an atrichous distribution, which refers to cells that do not have any flagella at all. An atrichous distribution means that these cells do not have any flagella. Notice that we're showing you a bacterial cell here that does not have any flagella branching off of it, and so, it is going to have an atrichous distribution. For example, Citrobacter freundii is an example of a bacteria that has an atrichous distribution because it has no flagella.

The next type of flagella distribution is a polar distribution, referring to flagella that are located at one or both poles of the cell. Here, we're showing you a bacterial cell that has a flagellum at just one pole of the cell. An example of this is Vibrio cholerae. Branching off of the polar are multiple distributions. The polar distribution at the top is really just a broad category with multiple types. We have 2a, 2b, and 2c, representing branches of a polar distribution.

For 2a, we have a monotrichous distribution, referring to just a single flagellum at one pole. Mono is a root that means one. As you can see here, a cell with a monotrichous distribution, a monotrichous polar distribution is shown. Vibrio cholerae is an example of a bacterium that has a monotrichous distribution.

Next, 2b is a lophotrichous distribution, referring to multiple flagella at a single pole of the bacterium. Notice that a bacterial cell is shown here, with multiple flagella branching off from just one end, one pole of the bacteria. An example of this is Helicobacter pylori, which has a lophotrichous polar flagellar distribution.

Lastly, the polar distribution 2c is an amphitrichous distribution. Amph is a root that refers to two. This is referring to one flagellum at each of two opposite ends. Notice that we have a single bacterial cell here with a flagellum coming out of each of two opposite ends. An example of this is Yersinia enterocolitica.

The third type of distribution is a peritrichous distribution, referring to flagella on the entire surface of the cell, with flagella branching off from virtually all different regions surrounding the cell surface. An example that has a peritrichous flagellar distribution is Bacillus cereus.

This concludes our lesson on the different types of flagellar distribution on bacteria. All of these flagella are important for the motility of the bacteria, allowing them to move throughout their environments. We'll be able to get some practice applying these concepts as we move forward. I'll see you all in our next video.

Which term is used to describe flagella that are found all over the surface of the bacterial cell:

• A. Peritrichous.
• B. Monotrichous.
• C. Amphitrichous.
• D. Atrichous.
• E. Lophotrichous.

Answer: (A)

Which of the following terms describes the presence of one flagellum at each pole of a bacterial cell?

• A. Lophotrichous
• B. Peritrichous
• C. Amphitrichous
• D. Dualtrichous
• E. None of the above

Answer: (C)

What kind of flagellar distribution is present on the surface of the bacterial cell in the image below?

• A. Peritrichous
• B. Lophotrichous
• C. Monotrichous
• D. Amphitrichous
• E. Atrichous

Answer: (B)

Here’s what students ask on this topic:

What is the difference between prokaryotic and eukaryotic flagella?

Prokaryotic and eukaryotic flagella differ in structure and function. Prokaryotic flagella are simpler, composed of a protein called flagellin, and rotate like a propeller to move the cell. They are anchored in the cell membrane and cell wall. Eukaryotic flagella, on the other hand, are more complex, consisting of a 9+2 arrangement of microtubules made of tubulin. They move in a whip-like manner and are covered by the cell membrane. These differences reflect the distinct evolutionary paths and cellular architectures of prokaryotes and eukaryotes.

What are the different types of flagellar distribution in bacteria?

Bacteria exhibit various types of flagellar distribution, which can aid in their identification. The main types are:

• Atrichous: No flagella present.
• Polar: Flagella located at one or both poles of the cell. This includes:
• Monotrichous: A single flagellum at one pole.
• Lophotrichous: Multiple flagella at one pole.
• Amphitrichous: One flagellum at each of two opposite poles.
• Peritrichous: Flagella distributed over the entire cell surface.

These distributions are crucial for bacterial motility and can be used to identify specific bacterial species.

How do flagella contribute to bacterial motility?

Flagella are essential for bacterial motility, allowing bacteria to move through their environment. They act like propellers, rotating to push or pull the cell. The rotation is powered by a motor protein complex located at the base of the flagellum, which uses the proton motive force (a gradient of protons across the cell membrane) to generate movement. This motility enables bacteria to navigate toward favorable conditions (chemotaxis) or away from harmful environments, enhancing their survival and adaptability.

What is the significance of flagellar distribution in bacterial identification?

Flagellar distribution is significant in bacterial identification because it provides clues about the species and its motility patterns. Different bacteria have characteristic flagellar arrangements, such as atrichous (no flagella), polar (flagella at one or both poles), and peritrichous (flagella all over the surface). For example, Vibrio cholerae has a monotrichous polar distribution, while Bacillus cereus has a peritrichous distribution. Identifying these patterns helps microbiologists classify bacteria and understand their behavior and ecological roles.

What are the examples of bacteria with different types of flagellar distribution?

Examples of bacteria with different types of flagellar distribution include:

• Atrichous: Citrobacter freundii (no flagella).
• Monotrichous: Vibrio cholerae (a single flagellum at one pole).
• Lophotrichous: Helicobacter pylori (multiple flagella at one pole).
• Amphitrichous: Yersinia enterocolitica (one flagellum at each of two opposite poles).
• Peritrichous: Bacillus cereus (flagella all over the surface).

These examples illustrate the diversity of flagellar arrangements and their importance in bacterial motility and identification.