Chemotaxis, Phototaxis And Other Taxes

Taxes or sometimes referred to as Taxis, refer to the movement that the organisms show when a stimulus like light or food is given to them or present in their surroundings. In other words, one can say that taxes are the response or action that an organism shows towards various stimuli. This is among the responses of innate behavioural. In this phenomenon, the organism shows movement either away or to words the source of the stimulus. There are different types of taxes based on stimulus type that include chemotaxis, phototaxis and other taxes like barotaxis, durotaxis, hydrotaxis, and more. 

Classification of Taxes

Taxes are an important phenomenon for most organisms. Classification of taxes can be done on two bases:

• Based on the stimulus type
• Presence of sensory organs

Based on stimulus type

This type of classification involves various taxes like chemotaxis, phototaxis and other taxes. The list of types of such taxes is as follows:

• Chemotaxis: The stimulus is chemicals
• Phototaxis: The stimulus is light
• Barotaxis: The stimulus is pressure
• Aerotaxis: The stimulus is oxygen
• Galvanotaxis or Electrotaxis: The stimulus is electric current
• Magnetotaxis: The stimulus is the magnetic field
• Thigmotaxis: The stimulus is physical contact
• Gravitaxis: The stimulus is gravity
• Durotaxis: The stimulus is stiffness
• Thermotaxis: The stimulus is a change in temperature
• Anemotaxis: The stimulus is wind
• Hydrotaxis: The stimulus is moisture
• Rheotaxis: The stimulus is fluid flow

Presence of sensory organs

• Klinotaxis: Environment Samples help in finding stimulus direction
• Tropotaxis: Bilateral Sense organs help in finding stimulus direction
• Telotaxis: A single organ help in finding stimulus direction

Examples of Chemotaxis, Phototaxis and other taxes

Chemotaxis

Chemotaxis refers to the movement that an organism shows to words a chemical stimulus. Organisms like bacteria, somatic cells, single-celled organisms, and multicellular organisms show their movements towards some specific chemicals present in their surroundings. To get food, bacteria move towards the area with the highest concentration of molecules that act as food for them, and they move away from those poisonous chemicals. Similarly, the rest of the organisms show chemotaxis. Chemotaxis in inflammation is increased when there are infections found in the organism. For example, lymphocytes and leukocytes show aberrant chemotaxis whenever any inflammatory disease condition like asthma.

Bacterial chemotaxis

In bacteria like E. coli, there are many flagella present on each cell. These flagella can rotate only in different manners; either they have a counterclockwise rotation or a clockwise rotation. Whenever there is a counterclockwise rotation, the bacteria can swim straightly. However, the flagellum has different directions in a clockwise rotation and makes the bacteria tumble. They have many transmembrane receptors and sense chemical gradients using them. These receptors are known as methyl-accepting chemotaxis proteins. These proteins send signals and result in different actions. Bacterial chemotaxis depends upon the nature of the chemical they are surrounded with; if it is poisonous, then bacteria will swim away from it.

Phototaxis

This refers to the moment an organism shows when the stimulus source is light. This phenomenon is beneficial for those phototrophic organisms as they can move towards the direction of light to perform photosynthesis. Whenever the organism’s movement is in the direction of light, it is termed positive. Whenever it is in the direction away from the source of stimulus, it is referred to as negative.

Other Taxes

Other taxes involve various types of taxes like Aerotaxis in which the organism moves when the oxygen concentration is changed. This type is found in aerobic bacteria. Electrotaxis refers to the movement of cells when there is an electric field present. The cells can detect and orient their structure in the electric field to repair their wounds. Thermotaxis happens when the organism moves concerning temperature. Some nematodes show thermotaxis whenever the temperature rises as they prefer less temperature. 

Conclusion

Taxis are important in many organisms because they help in the movement of the organisms. Taxes can be classified into various types depending upon the type of stimulus. Chemotaxis, phototaxis and other taxes play an important role in organisms like bacteria and phototrophic plants. Bacteria move in the direction of their food molecules wherever the concentration is high, and this is only because of chemotaxis. Similarly, phototrophic plants can move towards light due to phototaxis. So, taxes are an important phenomenon in all kinds of organisms, be it single-celled or multicellular.