Internship – Euglena Growth & Phototaxis Experiments Plan

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Euglena Growth Experiment:

  1. Prepare a culture medium suitable for euglena growth, which usually contains nutrients such as salts, sugars, and vitamins.
  2. Sterilize the medium and then inoculate it with a small number of euglena cells.
  3. Incubate the culture at an optimal temperature and light condition for euglena growth (typically around 25°C with a 12-hour light/12-hour dark cycle).
  4. Monitor the culture daily, and when the euglena population reaches a sufficient density, use a microscope and hemocytometer to count the number of cells and calculate the growth rate.

Phototaxis Experiment:

  1. Obtain a sample of euglena from the culture and place it on a microscope slide with a cover slip.
  2. Use a microscope equipped with a light source and a camera to observe the euglena and record their movement.
  3. Set the microscope to the desired light intensity and wavelength to stimulate phototaxis in the euglena.
  4. Observe the euglena movement in response to the light source and record their trajectories using the camera.
  5. Analyze the data to determine the degree and direction of phototaxis by the euglena.

It’s worth noting that euglenas are sensitive to changes in temperature, light, and nutrient availability, so maintaining stable conditions is crucial for reliable and repeatable experiments.


Impact of Light:

Euglenas are photosynthetic organisms that use pigments called chlorophylls to capture light energy for photosynthesis. Euglenas have two different types of chlorophylls, chlorophyll a and chlorophyll b, which absorb different wavelengths of light.

Red light has a longer wavelength and is absorbed by chlorophyll b, while blue light has a shorter wavelength and is absorbed by chlorophyll a.

Research has shown that red light promotes euglena growth, while blue light enhances euglena phototaxis. Red light also induces chloroplast development and increases the levels of photosynthetic pigments in euglena, which in turn increases the photosynthetic efficiency of the cells. In contrast, blue light activates the phototaxis response of euglena, which is the process of moving towards or away from a light source. Euglena exhibit positive phototaxis, meaning they move towards a light source, and blue light has been found to be particularly effective in stimulating this response.

Therefore, exposing euglena to different wavelengths of light can have varying effects on their growth and behavior, with red light promoting growth and blue light enhancing phototaxis.


Phototaxis is the process by which organisms move in response to a light source. It is a type of taxis, which is a directed movement of an organism in response to a stimulus. In the case of phototaxis, the stimulus is light.

There are two types of phototaxis: positive phototaxis and negative phototaxis. Positive phototaxis is when an organism moves towards a light source, while negative phototaxis is when an organism moves away from a light source.

Many organisms exhibit phototaxis, including bacteria, protists like Euglena, and animals like insects and fish. The ability to sense and respond to light is an important adaptation that allows these organisms to orient themselves in their environment and find sources of light that may be beneficial for their survival, such as food or mates.

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