Question

A thin, filamentous extension of cell wall required for a bacterial motility is called (a) Hook (b) Flagella (c) Tail (d) Mesosome

Short answer

The correct answer is (b) Flagella.

Step-by-step solution

Understand the question and options

This question is asking for the name of a thin, filamentous structure that extends from the cell wall and aids in bacterial movement. The options provided are Hook, Flagella, Tail, and Mesosome.

Evaluate each option

Evaluate each option to see if it fits the description. A hook and a tail are not precise terms used in cellular biology to describe structures responsible for bacterial movement. A Mesosome is an extension of the cell membrane that aids in cellular functions, but not specifically movement.

Select the correct option

According to the evaluations of the options, the correct answer would be Flagella. The flagella are long, thin, filamentous extensions of the cell wall that rotate like propellers, enabling the bacteria to move.

Key concepts

Flagella

Flagella are incredibly significant anatomical features of various bacteria, playing an essential role in their ability to move. These structures are slender, whip-like appendages that protrude from the cell body of certain bacteria and eukaryotic cells. In the realm of microbiology, flagella function as bacterial outboard motors, propelling the organisms through liquids.

Fueled by a flow of protons or, in some bacteria, sodium ions across the bacterial membrane, the flagellar motor rotates, allowing the flagella to act as a propeller. In solutions, they may spin at rates of hundreds of revolutions per second, giving bacteria the ability to travel up to tens of body lengths per second - a relative speed that surpasses that of a cheetah when scaled to size!

There are several types of flagella based on their arrangement and function: polar flagella present at one or both ends of the cell, and peritrichous flagella distributed over the entire surface of the cell. This distinction is critical, as the different flagellar placements are associated with distinctive movement patterns, giving each bacterial species its unique navigational abilities.

Cell wall extension in bacteria

The bacterial cell wall plays multiple roles in cell survival and function, but when we talk about cell wall extensions and bacterial motility, we are particularly referring to structures like flagella that extend from the cell wall and facilitate movement. It's critical to clarify that the flagellum is anchored in the cell wall and extends outwards, essentially mining the strength of the cell wall structure to act as a firm base for movement.

While flagella are the primary extensions associated with locomotion, some bacteria also have other structures like fimbriae and pili. Although these are not primarily for movement, they occasionally can participate in a type of movement called twitching motility or can aid in surface attachment, which may be indirectly involved in cell positioning and thus in the larger context of mobility.

Bacterial movement mechanisms

Bacteria have developed an assortment of movement mechanisms to navigate their environments. Aside from the well-known flagellar propulsion, some species of bacteria utilize non-flagellar forms of motility. For example, 'gliding motility' allows bacteria to move across surfaces without the need for flagella. Instead, they rely on mechanisms such as secretion of slimy polysaccharides, which act to pull or push the bacterial cell along a surface.

Another interesting method is 'twitching motility,' which is mediated by type IV pili, filamentous structures that can extend, attach to a surface, and then retract, pulling the cell forward in a jerky, inchworm-like motion. Additionally, 'swarming motility' is observed in groups of bacteria that exhibit a coordinated movement to cover solid surfaces; this behavior often requires flagella and is influenced by the production of surfactants that aid in reducing surface tension. Understanding these various bacterial movement mechanisms shines a light on the remarkable adaptive capabilities of these microorganisms to thrive in diverse habitats.