Bacterial Motility

exponential phase. There is a significant rate of cell division and multiplication of cells. Nutrients are used up rapidly until at least one nutrient is depleted, which begins to limit the growth.

The third phase of growth is called the stationary phase. This is directly caused by a lack of all of the necessary nutrients because they have been depleted. There is a reduction of metabolic activity and the consumption of all cellular proteins not deemed essential. Finally, there is a death phase, where there is a complete lack of necessary metabolic ingredients and the cells die off.

BACTERIAL MOTILITY

As already mentioned, bacteria have ways of being motile. The most common way that bacteria move is through the action of flagella, which are long filaments that act as propellers to move the cell. The flagellum will rotate through the use of a reversible “motor” at its base, whereby it uses the electrochemical gradient across the membrane and the movement of ions across this membrane in order to generate power.

Bacteria can have forward movement or tumbling movement. Tumbling helps the cell reorient themselves. There are four types of flagellated bacteria: monotrichous (one flagellum), amphitrichous (a flagellum at each end), lophotrichous (clusters of flagella at each end), and peritrichous (flagella all over the cell surface). There are stimuli in the environment that determine how and where the bacterial cell will move. There are phototaxis, chemotaxis, magnetotaxis, and energy taxis.