Light-induced absorbance changes associated with phototaxis in Dictyostelium

Area of Science:

• Cell Biology
• Biophysics

Background:

• Phototaxis is the movement of organisms in response to light.
• Dictyostelium discoideum exhibits phototactic behavior.

Purpose of the Study:

• To investigate light-induced absorbance changes in Dictyostelium discoideum.
• To determine if these absorbance changes are related to phototaxis.

Main Methods:

• Irradiation of cells and cell-free extracts with specific light wavelengths (520-600 nm).
• Measurement of absorbance changes at 411 nm.
• Analysis of light-induced absorbance changes in soluble and pellet fractions.
• Addition of dithionite to cell-free extracts.

Main Results:

• Reversible light-induced absorbance increase at 411 nm observed in Dictyostelium discoideum cells.
• Similar light-induced absorbance changes detected in cell-free homogenates and soluble fractions.
• Absorbance changes decayed in darkness with a half-time of approximately 7 seconds.
• Maximum absorbance change elicited by light around 560 nm, matching the spectral sensitivity of phototaxis.

Conclusions:

• The observed light-induced absorbance changes are associated with the phototaxis of Dictyostelium discoideum.
• The spectral sensitivity of the absorbance change correlates with the spectral sensitivity of phototactic migration.