Ch 3 Flagella

In a peritrichous bacterium, the flagella are all

bundled together in a very streamlined way, allowing for efficient movement.

Bacteria achieve directional movement by

changing the rotation of their flagella.

When tumbling, flagella are splayed out while rotating in a

clockwise direction, creating a looping motion and reorienting the cell toward the direction of the attractant.

Without a chemical gradient, flagellar rotation cycles between

counterclockwise (run) and clockwise (tumble) with no overall directional movement.

When running, flagella rotate in a

counterclockwise direction, allowing the bacterial cell to move forward.

Gram-positive and gram-negative bacteria have different basal body configurations due to

differences in the cell wall structure

Axial filaments of bacterial are also called

endoflagella

Bacteria can move in response to a variety of environmental signals, including

light (phototaxis), magnetic fields (magnetotaxis) using magnetosomes, and, most commonly, chemical gradients (chemotaxis).

A bacterium with a singular flagellum, typically located at one end of the cell (polar), is said to have a

monotrichous flagellum.

When an attractant exists, runs and tumbles still occur; however, the length of runs is longer, while the length of the tumbles is reduced, allowing

overall movement toward the higher concentration of the attractant.

Flagella that cover the entire surface of a bacterial cell are called

peritrichous flagella

Bacterial flagella act like

propellors

When no chemical gradient exists, the lengths of runs and tumbles are more equal, and overall movement is more

random

In a cell with peritrichous flagella, the flagella bundle when they rotate in a counterclockwise direction, resulting in a

run.

Endoflagells is found in

spirochetes (this means flagella is on each cide)

Flagella are

stiff spiral filaments composed of flagellin protein subunits that extend outward and spin in solution

Flagella

structures used by cells to move in aqueous environments

Purposeful movement toward a chemical attractant, like a food source, or away from a repellent, like a poisonous chemical, is achieved by increasing

the length of runs and decreasing the length of tumbles.

However, when a chemical gradient of an attractant exists,

the length of runs is extended, while the length of tumbles is decreased.

The basal body of flagella is

the motor and is embedded in the plasma membrane

Cells with lophotrichous flagella have a

tuft at one end of the cell.

However, when the flagella rotate in a clockwise direction, the flagella are no longer bundled, resulting in

tumbles.

chemotaxis

an overall directional movement toward the higher concentration of the attractant

Endoflagella is

anchored at one end of a cell, and rotation causes the cell to move

The basic structure of a bacterial flagella consists of

a basal body, hook, and filament

Cells with amphitrichous flagella have

a flagellum or tufts of flagella at each end.