In the presence of a chemical gradient, bacteria bias their movement by extending the length of runs and reducing the length of tumbles to migrate toward an attractant. If no chemical gradient is present, the durations of runs and tumbles are more equal, resulting in random overall movement.

Bacterial Movement in a Chemical Gradient

Chemotaxis is the movement of a bacterium in response to chemical gradients. This process allows the cell to travel toward chemical attractants, such as nutrients, or away from repellents, such as harmful substances, by adjusting the lengths of its runs and tumbles.

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There are many environmental signals bacteria sense that influence their movement in the form of a taxis. These taxes are: 
- Phototaxis
- Magnetotaxis
- Chemotaxis

Taxis Influencing Bacterial Movement 

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

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Magnetotaxis is the process by which certain bacteria sense magnetic fields and direct their movement. This behavior is facilitated by specialized intracellular structures called magnetosomes.

Magnetotaxis

Chemotaxis

Phototaxis is the directional movement of a bacterium in response to light stimulation.

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