Phototaxis Assay of Filamentous Cyanobacteria Using Focused Light Illumination

Begin with a dish containing a filamentous cyanobacteria culture positioned over a small window fitted with an LED-mounted holder in a dark room.

The LED illuminates the dish from below, creating a small light zone.

During incubation, the filamentous cyanobacteria migrate toward the illuminated center, demonstrating phototaxis.

Over time, the cyanobacteria migrate and accumulate at the illuminated center, forming a visibly dense bacterial zone.

After incubation, place a white paper beneath the dish to enhance contrast.

Capture an image of the illuminated area and analyze it using software.

Draw a line across the dish that passes through the center of the bacterial zone to generate a pixel intensity profile.

Compare the average pixel intensity outside and inside the bacterial zone.

Next, draw a line at the maximum intensity within the central region to determine the diameter of the bacterial zone, which represents cyanobacterial phototaxis.

Prepare LED holders where the five millimeter LEDs are mounted to irradiate an area of 20-millimeters square from below to above. Measure and adjust the LED intensities. Ensure that the whole setting is in a dark room or a closed, dark container.

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