key term - Tumbles

Definition

Tumbles are the erratic, random movements made by bacterial cells to change direction, typically caused by the reversal of flagellar rotation. This motion is part of the run-and-tumble behavior observed in prokaryotic cells during chemotaxis.

5 Must Know Facts For Your Next Test

1. Tumbles occur when the flagella rotate clockwise, causing the bacterium to reorient randomly.
2. The frequency of tumbles increases in unfavorable environments as bacteria seek more favorable conditions.
3. During a tumble, the bacterial cell momentarily stops moving forward and spins in place.
4. Chemoreceptors on the cell surface help determine whether a bacterium should continue running or initiate a tumble.
5. Tumbles are shorter and less frequent when bacteria move toward higher concentrations of attractants.

Review Questions

Related terms

Run: A smooth, linear movement where bacterial flagella rotate counterclockwise.

Chemotaxis:

The movement of an organism in response to chemical stimuli.

Flagella:

Long, whip-like structures that propel bacteria through their environment.