Microalgal membrane fluidity monitoring using DCVJ

This article proposes a flow cytometric methodology to monitor microalgae membrane fluidity using DCVJ (9-(2,2-DiCyanoVinyl)Julolidine). DCVJ is a methanol-soluble molecular rotor that inserts itself into the cell membrane. The tagging procedure was optimized in terms of cell-to-probe ratio, probe-to-water ratio, incubation time, and methanol toxicity. The model microalgae for this work was Chlorella vulgaris . The results demonstrated that the best incubation conditions are 1 mL sample at 1 MCell/mL, with a probe addition of 10 μ L at 10 mM, incubated in the dark for 20 min. In addition, the protocol shows some robustness as cell concentration can be decreased to 0.1 MCell/mL, incubation time extended from 20 to 30 min, and methanol quantity quadrupled without perturbing the signal. Once optimized, the protocol was applied to monitor microalgae membrane acclimation to hyperosmotic (rigidifying) conditions and their reversion (fluidizing). An advanced signal treatment is required to access membrane fluidity properly. Ultimately, the protocol allowed monitoring for two passages, delivering explainable and repeatable results. • Chlorella vulgaris were tagged using DCVJ to measure membrane fluidity. • Cell-to-probe ratio, incubation duration and illumination were optimized. • DCVJ alters fluorescence membrane signal. • A model is proposed to compensate for the signal alteration. • Cell membrane fluidity was successfully tracked over an hyperosmotic culture.