Describe how a bacterium with peritrichous flagella moves. How does this allow cells to move up a gradient of a an attractant or down the gradient of a repellent? Solution The flagella is present in bacteria. They can take 100\'s of rotations. By taking these rotations they can move freely. If a bacterium has a peritrichous arrangement of flagella, such as Escherichia coli, Salmonella, Proteus, and Enterobacter, the flagella rotates in a counterclockwise directionwhich causes them to form a single bundle that propels the bacterium in long, straight or curved runs without a change in direction. Some flagella which rotates in clockwise diraction forms in the bundle causes the flagellas to be pushed apart from the bundle triggering a tumbling motion. Every time the bacterium tumbles it rerotates itself in a different directions. In the presence of a chemical gradient, their movements become biased. When the bacterium is moving away from higher concentrations of repellents or towards higher concentrations of attractants the runs become longer and the tumbles less frequent. Therefore an increasing concentration of attractant or decreasing concentration of repellent in both the conditions are beneficial causes less tumbling and runs longer; a decreasing concentration of attractant or increasing concentration of repellent both conditions are harmful causes normal tumbling and a greater chance of reorienting in a \"better\" direction. As a result, the organism\'s net movement is toward the optimum environment.. Most of the bacteria with polar flagella like, such as Pseudomonas aeruginosa, they can rotate their flagella both in clockwise direction and counterclockwise direction. If the flagellum is rotating counterclockwise directions, it pushes the bacterium forward. When it rotates clockwise directions, it pulls the bacterium backward. These bacteria can change their direction by changing the rotation of their flagella. Some bacteria with polar flagella, such as Rhodobacter sphaeroides, can only rotate their flagellum clockwise. Therefore in this case, clockwise rotation pushes the bacterium forward. Every time the bacterium stops, it reorients itself in a new direction..

1. Describe how a bacterium with peritrichous flagella moves. How does this allow cells to move
up a gradient of a an attractant or down the gradient of a repellent?
Solution
The flagella is present in bacteria. They can take 100's of rotations. By taking these rotations
they can move freely. If a bacterium has a peritrichous arrangement of flagella, such as
Escherichia coli, Salmonella, Proteus, and Enterobacter, the flagella rotates in a
counterclockwise directionwhich causes them to form a single bundle that propels the bacterium
in long, straight or curved runs without a change in direction. Some flagella which rotates in
clockwise diraction forms in the bundle causes the flagellas to be pushed apart from the bundle
triggering a tumbling motion. Every time the bacterium tumbles it rerotates itself in a different
directions. In the presence of a chemical gradient, their movements become biased. When the
bacterium is moving away from higher concentrations of repellents or towards higher
concentrations of attractants the runs become longer and the tumbles less frequent.
Therefore an increasing concentration of attractant or decreasing concentration of repellent in
both the conditions are beneficial causes less tumbling and runs longer; a decreasing
concentration of attractant or increasing concentration of repellent both conditions are harmful
causes normal tumbling and a greater chance of reorienting in a "better" direction. As a result,
the organism's net movement is toward the optimum environment..
Most of the bacteria with polar flagella like, such as Pseudomonas aeruginosa, they can rotate
their flagella both in clockwise direction and counterclockwise direction. If the flagellum is
rotating counterclockwise directions, it pushes the bacterium forward. When it rotates clockwise
directions, it pulls the bacterium backward. These bacteria can change their direction by
changing the rotation of their flagella. Some bacteria with polar flagella, such as Rhodobacter
sphaeroides, can only rotate their flagellum clockwise. Therefore in this case, clockwise rotation
pushes the bacterium forward. Every time the bacterium stops, it reorients itself in a new
direction.