Glucose as a Mitigator of Cadmium-Induced Toxicity in Chlorella sp.: Insights from Cell Division and Photosynthesis

Cadmium (Cd) pollution is a growing environmental challenge worldwide, impairing cellular integrity and transcriptional regulation across species and undermining ecosystem stability. This study investigates the effects of Cd 2+ stress on Chlorella pyrenoidosa in terms of growth, cell division, and photosynthetic function, and evaluates the alleviating role of soluble organic carbon supplementation, using glucose as a representative source. Results indicate that Cd 2+ exposure markedly suppresses algal growth, disrupts photosynthetic systems, reduces chlorophyll content, diminishes key photosynthetic metrics, and interferes with cell wall degradation. Biomass and specific growth rate declined from 0.6 g L -1 and 0.49 d -1 in controls to 0.38 g L -1 and 0.42 d -1 under Cd 2+ stress, but recovered to 0.95 g L -1 and 0.61 d -1 with glucose addition. Glucose supplementation substantially counteracted these inhibitory effects, partially reviving photosynthetic activity through enhanced QA-to-QB electron transfer and stabilization of porphyrin metabolism. Transcriptomic profiling revealed that Cd 2+ downregulated genes involved in cellulose degradation while upregulating those associated with lignin biosynthesis; glucose treatment restored the expression of lignin-related genes to near-control levels. Collectively, our findings demonstrate that glucose alleviates Cd 2+ toxicity in C. pyrenoidosa by restoring photosynthetic competence and cell division capacity, thereby elucidating key metabolic pathways underlying heavy-metal detoxification. • Glucose increased Chlorella biomass by counteracting Cd inhibition. • Cd 2+ disrupts cell wall degradation and photosynthetic systems. • Glucose co-treatment restored the cell wall degradation and chlorophyll homeostasis.