Functional Validation and Mechanistic Insights into Cadmium Removal by the Green Microalgae Coelastrella tenuitheca S93-3

Coelastrella tenuitheca strain S93-3 is a green microalga that demonstrates remarkable tolerance to heavy metal stress. It is a promising candidate for bioremediation applications, strongly resistant to cadmium, and an essential organism for phytoremediation studies. However, the molecular mechanism of the response of C. tenuitheca S93-3 to cadmium stress, and the key regulatory genes for specific detoxification processes are poorly understood. Overall design: The isolated microalgal strain S93-3 cultured in modified BG-11 liquid media, containing a gradient of cadmium chloride (CdCl2) concentrations: 5, 10, 15, 20, 25, 30, and 50 mg/L. All cultures were incubated under controlled conditions at 28°C with constant shaking at 150 rpm for a duration of 7 days. Growth was monitored daily by measuring OD680 and assessing overall culture status. Dry biomass was quantified at the endpoint of the experiment. The half-maximal inhibitory concentration (IC50)—the cadmium concentration required to reduce the dry biomass by 50% compared to the control—was calculated from this data.