Question

How do various types of bacteria move? a. by the use of flagella, composed of a filament, hook, and motor b. by means of pili, which help cells twitch or glide along a surface c. by using gas vesicles to regulate buoyancy in water bodies d. All of the above are used by bacteria for movement. e. None of the above are used by bacteria for movement.

Short answer

D. All of the above are used by bacteria for movement.

Step-by-step solution

Understand bacterial movement through flagella

Flagella are tail-like structures that help bacteria move. They are composed of a filament, a hook, and a motor. When the motor rotates, the entire flagella spins, causing a propeller-like motion, leading to the bacteria's movement. So, option a is correct.

Understand bacterial movement through pili

Pili are short, hair-like structures on the surface of bacteria. They can be used by bacteria to twitch or glide along a surface. So, option b is also correct.

Understand bacterial movement through gas vesicles

Gas vesicles are small, rigid protein-bound compartments that provide buoyancy to cells by regulating their gas content. They allow some bacteria to adjust their buoyancy and move vertically in water bodies. So, option c is correct.

Conclude

Taking into account all the above observations, we can conclude that various types of bacteria can use any or all of these mechanisms for movement. Hence option d is the correct choice - All of the above are used by bacteria for movement.

Key concepts

Flagella

Flagella are fascinating structures that allow bacteria to navigate their surroundings efficiently and with remarkable speed. These tail-like appendages are made up of three main parts:

• Filament: This is the long, whip-like part that extends from the bacterial cell.
• Hook: A flexible joint that connects the filament to the motor.
• Motor: Located at the base within the bacterial cell membrane, it powers the rotation of the flagella.

The motor works by utilizing the flow of ions across the bacterial membrane, turning the hook and filament in a circular motion. This movement propels the bacterium forward, much like a propeller moves a boat.
Such motion allows bacteria to move toward favorable environments or away from hostile conditions. This directional movement is known as "chemotaxis," a vital survival skill for many bacterial species. Flagella are not only critical for locomotion but also play a significant role in helping bacteria colonize new environments.

Pili

Pili, often referred to as fimbriae, are tiny, hair-like structures found on the surface of many bacterial cells. Unlike flagella, pili are not used for swimming through a liquid environment; instead, they are instrumental in surface-related movements and interactions.
Pili facilitate a form of movement called "twitching" or "gliding" motility, which allows bacteria to move across solid surfaces. They function by extending and retracting, pulling the bacterial cell along as if it were hauling itself with tiny grappling hooks. This mechanism is particularly useful in environments where fluids are minimal, such as mucous membranes or other solid surfaces.
Beyond movement, pili are crucial for bacterial adhesion, helping bacteria attach to host cells, surfaces, and each other. This adhesive ability is essential for forming biofilms, which are communities of bacteria that stick together and can be resistant to antibiotics. Pili help bacteria not just to move but also to survive and proliferate in competitive and tough environments.

Gas Vesicles

Gas vesicles are intriguing structures used by some bacteria, most notably those found in aquatic environments. They are protein-bound compartments within the cell that help regulate its buoyancy.
Gas vesicles work by trapping or releasing gases, allowing the bacteria to float or sink in a water column. This buoyancy control is similar to how a submarine manages its depth, enabling bacteria to move to optimal light or nutrient conditions in their aquatic habitats. The ability to adjust buoyancy is vital for photosynthetic bacteria that need to be near the surface to capture sunlight.
These vesicles are rigid, providing structural support to the cell and protecting the gas-filled compartments from collapsing under external pressure. The adaptability afforded by gas vesicles is a crucial survival strategy, helping bacteria maintain access to ideal light and nutrient conditions, thus ensuring their continued growth and replication.