Multiple light inputs control phototaxis in Synechocystis sp. strain PCC6803

Area of Science:

• Microbiology
• Photobiology
• Cellular Physiology

Background:

• Cyanobacteria, like Synechocystis sp. strain PCC6803, display phototaxis, the directed movement in response to light.
• Understanding the photoreceptors and light pathways governing these behaviors is crucial for comprehending microbial adaptation.

Purpose of the Study:

• To investigate the light input pathways and photoreceptors responsible for positive and negative phototaxis in Synechocystis sp. strain PCC6803.
• To elucidate the spectral sensitivities and fluence rate responses of phototactic behaviors.

Main Methods:

• Utilized a glass slide-based phototaxis assay to study individual cell behavior.
• Determined action spectra and fluence rate-response curves for wild-type and mutant strains.
• Analyzed phototactic responses under varying light intensities and wavelengths.

Main Results:

• Positive phototaxis is a low fluence response, spectrally sensitive to red light (645, 704 nm), and mediated by the TaxD1 protein.
• Negative phototaxis is primarily a high-intensity blue light response (peak sensitivity ~470 nm).
• A taxD1 mutant exhibits negative phototaxis across a broader spectral range, indicating TaxD1's specific role in positive phototaxis.

Conclusions:

• The TaxD1 protein acts as a red light photoreceptor, mediating positive phototaxis in Synechocystis.
• Negative phototaxis is regulated by distinct, yet unidentified, blue light photoreceptors.
• Synechocystis sp. strain PCC6803 employs multiple light-sensing pathways to control directed movement.