Chlamydomonas reinhardtii cells adjust the metabolism to maintain viability in response to atrazine stress

•Results indicate energy alterations in C. reinhardtii cells exposed to atrazine.•Cellular metabolic activity decreased in atrazine treated cells.•Cytoplasmic and mitochondrial membrane potentials were altered in exposed cells.•Atrazine exposed cells were able to maintain cellular viability.•RNA-Seq revealed upregulated transcripts related to heterotrophic energy generation.

Chlamydomonas reinhardtii cells were exposed to a sublethal concentration of the widespread herbicide atrazine for 3 and 24 h. Physiological parameters related to cellular energy status, such as cellular activity and mitochondrial and cytoplasmic membrane potentials, monitored by flow cytometry, were altered in microalgal cells exposed to 0.25 μM of atrazine. Transcriptomic analyses, carried out by RNA-Seq technique, displayed 12 differentially expressed genes between control cultures and atrazine-exposed cultures at both tested times. Many cellular processes were affected, but the most significant changes were observed in genes implicated in amino acid catabolism and respiratory cellular process. Obtained results suggest that photosynthesis inhibition by atrazine leads cells to get energy through a heterotrophic metabolism to maintain their viability.